Category: HortInsights

Copper Based Fungicides

Copper Based Fungicides

By Steve McGrane MAIH RH Images/ Steve McGrane

What are they? Are they safe for the environment? How to use copper effectively in a horticultural setting.. the alternatives..

Fungal infection on a geranium. Image/ Steve McGrane

Fungal infections can be highly impactful to many plants, including vegetables, fruit and ornamentals. Copper is an effective fungicide for controlling fungal, viral and bacterial infections. However a large body of research indicates copper fungicides have a considerable impact to humans and the environment.

The reality is, many treatments used in horticulture have detrimental effects. We can’t entirely stop the use of such chemicals so being ‘well informed’ and understanding effective alternatives, is the most practical course of action.

How Does Copper Work as a Fungicide?

Copper impairs cellular functions in viruses, fungi and bacteria through ‘peroxidation’ (oxidation) of cells leading to inaction by lipids resulting in the collapse of cells walls, attacking virus structural integrity, inhibiting protein and enzyme chemical disruption by binding to surfaces. These actions either prevent fungal spores from completing essential metabolic functions or cause desiccation (drying out) through destruction of cell walls.

A fungal disease that attacks kangaroo paws (Anigozanthos) is Alternaria alternata. This disease can be controlled in perennial varieties of kangaroo paws (having a rhizome), by cutting back leaves to within a cm of the soil, post flowering. Copper is also effective in addressing a single attack of the disease. However subsequent infections are better controlled through seasonal removal of infected leaves. Image/ Steve McGrane

Implications of using Copper in Horticulture

Copper is a Heavy Metal

Copper is a naturally occurring element termed a heavy metal, and generally occurs at very low levels in the natural eco system but accumulates in the environment largely through horticultural and commercial activities.

Note: A heavy metal is best described as an element that is dense in volume and resistant to break down. While copper can bind with proteins and remain biologically bound, it can become ‘free’ (as occurs in the use of copper fungicide preparations) and becomes toxic. Copper accumulates in soils, seabeds, humans and plant tissue.

Low Levels of Copper Kills Soil Biota

At very low levels copper becomes toxic to plants, humans and importantly, soil organisms, including worms. Relatively low concentrations prove toxic to soil organisms (Helling et al. 2000).

Copper sprays are harmful to all aquatic life (including fish), livestock and soil biota. Small elevations of copper in the soil reduce beneficial mycorrhizae associations (Liao et al. 2003). Fungi are essential for symbiotic relations with plants.

Copper sulfate kills soil biota and, insects (e.g. bees) when sprayed as an anti-fungal (Bogomolov et al. 1996, Böckl et al. 1998). Impact on pollinators highlights the need to be aware of timing of applications. Spraying fungicides when pollinators are present is counterproductive and environmentally irresponsible.

Copper Anti-Fungal Compounds Encourage ‘Pest Resistance’

Research shows disease and pathogenic fungi develop resistance to copper treatments making copper fungicides ineffectual overtime and we should therefore have a mix of chemical and cultural strategies e.g. rotate crops or improve air flow in the garden or nursery. Refrain from overhead watering.

Copper Stays in the Soil

In most soils, copper residues are likely to remain indefinitely, and will continue to influence the health of the soil. This has implications for future land management and human health.

Organic Matter Does Not Lower Copper Levels in Soils

Thrupp (1991) found that copper, arising through Bordeaux application, tended to be associated with areas of high organic matter build-up. Hence even good levels of organic matter, will not assist in reducing copper toxicity but rather exacerbate. Hence the message is, use copper sparingly because you can’t put the genie back in the bottle.

Liquid Copper. Image/ Steve McGrane

Using Fungicides Effectively

Apply fungicides before the development of buds, or after in the case of liquid copper and ‘certified organic’ fungicides that are potassium based or other compounds such as milk that do not have a corrosive effect on plant tissue.

Applying fungicides before bud burst is also necessary to prevent fungal spores’ transferring to the plants androecium (male sexual parts of the plant) after buds open and develop further during fruit set and fruit development. Liquid copper (discussed further below) can be applied after bud burst without damaging tissue.

Examples of Common Copper Fungicides and Their Uses

A copper formulation used pre-emptively for the treatment of fungus (mildew and botrytis) is Bordeaux. Bordeaux uses copper ions and a slurry of lime to prevent fungal spores from germinating by blocking an essential enzyme.

Bordeaux is typically applied to deciduous trees in winter. Note: alternatively, ‘organically certified’ Bio Dynamic Pastes, are an effective alternative to Bordeaux when applied in winter.

Copper Oxychloride a historically effective treatment for fungal attack. Image/ Steve McGrane

Another common copper fungicide, Copper Oxychloride, controls fungal and bacterial attacks on trees and vegetables; This includes diseases like mildew, anthracnose, banana leaf speckle, leaf spot, septoria leaf spot, black spot, melnose, lemon scab, smoky (sooty) blotch, brown rot, collar rot and pink disease etc. Since copper oxychloride becomes toxic in the soil, use removable mats under plants when spraying, to avoid contamination of soil.

More recently ‘liquid’ forms of copper (copper hydroxide), have become popular as anti-fungal treatments. Liquid copper is more effective due to its inter-laminar nature (nano in size, entering leaf tissue) and therefore more persistent and less effected by wet weather. However it is also more persistent in soils.

Note: fungicides are only disruptive but not a cure, as fungal spores survive treatments.

Copper, can be too Much of a Good Thing, even for plants!

Although copper is required in the soil for plant health, it easily becomes toxic causing iron chlorosis (yellowing) or stopping photosynthesis turning leaves dark green before becoming white. Excessive copper, damages roots causing wilt or death.

Note: ‘Lesser quality’ copper supplements, or anti-fungal products, may contain high levels of undesirable heavy metals such as arsenic, mercury, lead and cadmium.

Combine a ‘potassium based’ fungicide with plant oils for stronger efficacy. Image/ Steve McGrane

Alternate Fungicides

Effective antifungal treatments with minimal environmental effects are as follows (Alva AK, Huang B, Paramasivam S, 2000):

  • Use ‘covers crops’, to reduce pathogenic fungi as an alternative to copper.
  • Ensure good air flow around plants and prune fruit trees in winter.
  • Apply a Bio Dynamic Tree paste after pruning each year (4 parts cow manure, 2 parts diatomaceous earth or silica, 3 part potters clay, or garden clay, add rain water to make a slurry which is applied with a brush)
  • Use a potassium based fungicide pre and post ‘bud burst’.
  • In the nursery or garden, use drip irrigation instead of overhead watering to reduce fungal growth.
  • Add regular amounts of compost and inoculated compost (beneficial fungi strains that attach to pathogens)
  • Surfactants and bio surfactants (oils or fats used to lower surface tension and discourage leaf fungi) e.g. Eco Oil
  • Compost teas (good bacteria prevent harmful fungal spores establishing)
  • pH modifiers and bicarbonates (changing the pH prevents fungal spore germination) calcium and silicone sprays e.g. Milk products, create an alkaline surface not conducive to fungal spore germinations.
  • Molasses; mixed at a rate of 1:10 in water and sprayed on plant leaves.
  • Essential oils:
    – Citronella oil
    – Jojoba oil
    – Nimbin (neem oil)
    – Oregano oil
    – Rosemary oil
  • Wettable Sulphur


October 26, 2017, Society of Environmental Toxicology and Chemistry
Van Zwieten M, Stovold G, Van Zwieten L (2004b) Literature Review and Inventory of Alternatives to
Copper for Disease Control in the Australian Organic Industry. A report for the Rural Industries
Research and Development Corporation. RIRDC Project DAN-208A. ISBN 0 7347 1590 0, 101p
NSW Department of Primary Industries, June 2017
Kay T. Ho et al, Effects of micronized and nano-copper azole on marine benthic communities, Environmental Toxicology and Chemistry 2017.
A report for the Rural Industries Research and Development Corporation. RIRDC Project DAN-208A. ISBN 0 7347 1590 0, 101p. Ware GW (1978) ‘The Pesticide Book.’ (W.H. Freeman and Company: San Francisco).

Green Is The New Black!

Green Is The New Black!

By Simon Holloway MAIH Images/ Simon Holloway, Vegepod

Vegepod has noted that of all 11 years of operation they have never witnessed such a marked rise in edible gardening as compared to the last two years. This has clearly reflected the boom across the entire horticulture industry since COVID19 first struck, but edible gardening in particular has seemed to have climbed to new ‘trendy’ heights due to its appeal on a few levels beyond ornamental gardens.  

So much so that even popular celebs and esteemed Australians have jumped on the grow-your-food trend and have been brandishing themselves in the media using edible gardens like Vegepods. 

The rise of therapeutic horticulture since covid’s enforced ‘health check’ on all citizens has meant wellness is now seen through a more holistic lens, including aspects such as mental health, emotional health, physical health and social / spiritual meaning. This has all culminated in a new-found consumer intention for sustainable action, self-sufficiency, organic living, family bonding and healthy eating from within one’s own home.

Vegepod reports seeing a 200% increase sales over the last two years whilst meeting the new demand for the trend.  Vegepod’s Head of Community and co-founder, Simon Holloway, says “Thanks to contained edible garden beds like Vegepod, these days anyone can grow their own food no matter the space, ability or background.  Despite a crowded market and information overload around wellness, edible gardening is finally a ‘wellness trend’ that absolutely anybody and everybody can have access to and enjoy ..and it’s a meaningful one!”

Simon also noted an interesting interaction with a journalist from a major national paper asked during the thick of the initial outbreak. He said “The lady asked me if Vegepod and the hort industry as a whole felt guilty about having some success during such troubling times for others. I was taken aback by the ridiculous question at first but then proceeded to respond by saying I found that offensive and it’s not the case at all. On the contrary, if there was one wholesome trend and industry for individuals, society and the entire planet that did deserve a shot in the arm – then it was (edible) gardening!” (Note, that particular question and answer was not published in the final article!).

So Vegepod says they salute all and sundry who have taken up edible gardening in the last two years and who are proudly showing those activities off!

Industry Memberships See New Book Reach Fruition

Industry Memberships See New Book Reach Fruition

By Daniel Austin MAIH RH Images/ Daniel Austin

Author and lecturer Dan Austin. Image/ Daniel Austin

Memberships with multiple industry bodies are one of the most valuable things a person can do to foster a successful career, and a membership with the Australian Institute of Horticulture has been the latest of mine.

I thought the Institute’s HortInsights publication would be a great way to introduce myself and connect with new faces across Australia. My name is Dan Austin and I am a lecturer in horticulture at TAFESA’s Urrbrae Campus in South Australia, among a few other roles.

Though the membership with AIH is my latest, my first membership was with a group known as the International Plant Propagators Society (IPPS). It was a membership that, many moons ago, gave me the opportunity to travel to South Africa to study the country’s nursery industry through a scholarship. I could not have imagined the impact the experience would have on my career and I credit IPPS as the trigger for what has become a life of working on horticultural projects across the globe.

If there is one piece of advice, I drill in to my students ad nauseum, it is the value of industry memberships.

In the years since that initial study tour, industry memberships have provided me with opportunities to work in horticulture in far flung places from the tropical Solomon Islands to arid Israel and other countries in between. As a result, I am happy to be able to share a new book for plant lovers everywhere – Off The Garden Path: Green Wonders Of The World.

Off the Garden Path cover. Image/ Daniel Austin

Off The Garden Path was initially planned as a celebration of botanical photography to share some of the remarkable horticultural enterprises I have been fortunate enough to be involved with around the world, in the hope of inspiring gardeners and travellers alike. However, it soon became a book for anyone with an interest in the wonders of our planet.

Over the years since its conception, the project has become an international collaboration with numerous centres of horticultural excellence abroad offering assistance. From the Bogor Botanic Gardens in Indonesia to the Jerusalem Botanic Gardens in Israel, even Singapore’s Gardens by the Bay have played a significant part in the text reaching fruition.

A non-fiction resource, Off The Garden Path: Green Wonders Of The World is full of botanical factoids. As an example – did you know that high in the Himalayas, Nepali beekeepers produce a potent psychoactive honey used recreationally and in traditional medicine by ensuring their bees feed only on poisonous rhododendron flowers?

From exploring the weird and wonderful world of parasitic plants to delving into the lives of plants that survive through symbiosis and mutualism, the content is diverse.


Rafflesia pricei a parasitic plant endemic to Borneo. Image/ Daniel Austin

Living root bridges in Northeast India another of the book’s featured sites. Image/ Daniel Austin

As the title suggests the text takes readers off the beaten track to locations less travelled, from remote tribal villages in Tanzania, and floating gardens in Myanmar to enormous centre pivot farms in the deserts of Jordan. The sites featured aren’t your average gardens and the people are not your average gardeners in the publication, which offers a chance to travel vicariously in a world of restrictions and inspiration for when things open up again.

A matt form of the book is available through a plethora of online distributors, but premium gloss copies can also be ordered through It is a great addition for the green thumb or travel bug in your life.

The book has been well-received and I hope you enjoy it as much as I enjoyed putting it together. Also, keep an eye out next year for the second book in the series Off the Garden Path: Green Wonders of Australia.

The Role Organics Can Play Post COP26

The Role Organics Can Play Post COP26

By Christopher Rochfort MAIH, CEO CORE

Cross-Sectional design of a Bio-Swale system with Bio-Filter treating road run-off before discharging to waterways. Image/ Chris Rochfort, CORE

It’s not easy sometimes seeing the wood for the trees. This could be the case with for the horticulture industry as it navigates its way through COP26 and a strong focus on energy emissions. There are the obvious benefits horticulture can offer such as more shade trees for addressing the heat island effect and greening of the urban landscapes but there is more much more.

But first I want to take a step back and recognise the role plant material plays in methane generation in landfills if not recycled. I’ve been at the forefront of organics recycling since 1992 helping to form two key industry organizations, conducting government supported research into markets for end products and initiating Australian Standards for Composts, Soil Conditioners and Mulches.

By far the most important body of work though has been through CORE (The Centre for Organic Research & Education) in unpacking the critical role organic material can play in water management.

By water management I’m not only referring to moisture holding capacity benefits; for instance I’m referring to the role organic material can treat and remove pollutants that are in urban, industrial and agricultural run-off. This run-off often contains nutrients, heavy metals, toxic compounds such as hydrocarbons and microplastics.

Recycled organics when combined with a number of other materials such as glass, sand, charcoal and other recycled materials can physically, chemically and biologically treat the above-mentioned pollutants. We have even removed uranium and PFAS, for instance. The removal rates are often in the 90th percentile and it is difficult to find any other product or machine for that matter that can do better.

Manly, NSW Stormwater Treatment & Reuse System showing Bio-Filter surrounding drainage and storage tanks used to irrigate grass areas of Manly beach using treated stormwater. Image/ Chris Rochfort, CORE

Lyne Park, Rose Bay Sydney during rainfall event showing run-off dispersing over Bio-Filter bed. Image/ Chris Rochfort, CORE

Cross Sectional design for Lougheed Highway, BC, Canada using CORE designed Bio-Filtration Media in median strip to protect nearby salmon streams receiving road run-off. Image/ Chris Rochfort, CORE

Through CORE, we have conducted long-term research on materials and pilot sites around Australia and fifteen other cities around the world where the results have been replicated. Traditionally city engineers and researchers had opted for sand filter technology to remove pollutants from run-off using the same principles as a “sand filter” used in swimming pools.

However, they soon tried to adopt the technology to vegetated filter systems such as rain gardens and bioswales with often less than favourable results. Testing was carried on adding a small amount of organic matter however they found this leached impurities into the waterways. This was because the organic matter chosen was unstable and not suited for the purpose.

CORE research has found that if the organic matter is properly prepared and particle sized there is almost no leaching occurring. This finding has enabled a higher percentage (up to 50 %) or organic matter can now be used in biofiltration systems that results in optimum plant growth. The plants can also contribute to the treatment process through “phyto-remediation”.

Another important factor is these systems resilience in the era of climate change with plants coping much better in either drought or localised flood events. A wider palette of plants can be used whereas with sand filters primarily monocotyledon plants were used. With increased organic matter levels there are other benefits such as reduced flooding and higher carbon sequestration.

In summary plant material and horticulture have a lot to offer in cleaning waterways and managing climate change.

The Renovation of a Historic Kitchen Garden: Chateau Holtmühle in the Netherlands

The Renovation of a Historic Kitchen Garden: Chateau Holtmühle in the Netherlands

By Andrea Govaert MAIH

On a recent visit to the Netherlands, I stumbled on a restored castle complex. It was autumn, and the area was ablaze with the light and colours of a typical northern landscape.

Autumn colours at the grounds of Chateau Holtmühle, Tegelen, the Netherlands. Images/ Andrea Govaert

Chateau Holtmühle, jointly with its associated properties, grounds and gardens of 37 hectares, is situated in the south of the Netherlands, in the village of Tegelen, one of many villages scattered along the banks of the river Maes, close to the borders with Germany.

Parts of the castle date back to the 14th century. Its principal construction was completed in the 17th century. The municipality of Tegelen acquired the crumbling castle complex in 1967. After a prolonged period of restoration, Chateau Holtmühle was ‘reborn’ in 1993 and converted into a hotel, whilst keeping the history and classical architecture of the complex.

Initially, the gardens were not considered in the overhaul and thus had fallen into complete disrepair. However, at the initiative of current head gardener Henk Kruizinga, the gardens were restored and opened to the public in 2014.

The concept of a kitchen garden evolved from the medieval hortus conclusus (‘enclosed garden’), established by monastic communities that relied on growing their own produce for survival. Therefore a hortus conclusus was, and still is, primarily utilitarian. The beauty of a kitchen garden lies in the quiet geometrical order of (raised) garden beds, dedicated to different types of produce.

A kitchen garden is often segregated from a ‘leisure garden’ by walls, fences, moats or hedges to protect the produce from straying animals, thieves as well as the elements. The original design of the kitchen garden at Chateau Holtmühle, feeding the castle inhabitants, is based on this concept. The garden is surrounded by a moat filled with water lilies, irises, rush and other marginal plants as well as trained Fagus sylvatica, Carpinus betulus and clipped yew hedges.

Left: Henk Kruizinga, head gardener at Chateau Holtmühle. Right: Clipped yew surround the kitchen garden. Images/ Andrea Govaert

The garden itself is divided into garden beds dedicated to culinary and/or medicinal plants and herbs, such as Rucola eruca vesicaria, Borago officinalis, Mondarda fistulosa, various mint varieties and common herbs such as sage, parsley, garlic, and basil.

Additionally there are beds containing annuals and perennials with cosmetic qualities and edible flowers such as Lavandula augustifolia, Calendula officinalis, Matricia chamomilla, Anthriscus cerefolium, Centaurea cyanus, Hesperis matronalis, Viola tricolor, Tropaeolum majus and finally, the majestic Verbascum nigrum (black mullein). With its finely haired leaves and long straight stems, it was dried and dipped in resin to use as torches already by the Romans until late in the 16th century.

The kitchen garden also has an orchard with neat rows of apple, plum, and cherry trees, as well as Ficus carica and Mespilus germanica (medlar). The latter was commonly planted in German and Dutch monastic gardens for its brownish fruits that are best eaten raw when slightly rotten (particularly after the first frost), or eaten cooked in compotes and jams.

Unlike its botanical name suggests, the tree originates from the area around the Black and Caspian Seas. Today it is increasingly rare in Germany and the Netherlands and its fruits are not very popular.

Left: The garden beds, at the end of the season. Right: Fruit of the Mespilus germanica. Images/ Andrea Govaert

Finally, the orchard contains a Vitex agnus-castus, (the Vitex, chaste tree or monk’s pepper), a native of the Mediterranean basin, that was first described by Linnaeus in 1753. Its fruits, about the size of a peppercorn, were reportedly used to reduce the libido of monks during the middle ages, hence its common name ‘monk’s pepper’. It is still frequently harvested to treat other ailments.

Vitex agnus-castus surrounded by clipped Lavandula augustifolia bushes. Image/ Andrea Govaert

The restored garden operates on similar principles as its 17th-century predecessor: it supplies fresh, organic produce to the chefs employed at the Chateau, including eggs, herbs, honey, fruits, (edible) flowers and mushrooms.

Further, the garden is a training ground for young horticultural staff, who subsequently may find employment in nearby horticultural industries, and often return regularly as volunteers to tend to the garden. Finally, the garden is a source of inspiration and knowledge for aspiring gardeners, volunteers, visitors as well as horticulturalists involved in the increasingly popular concept of community kitchen gardens, which currently sprout in many places around the world, also here in Australia.

To this effect, renovated historical kitchen gardens provide an endless source of knowledge, including the botanical history of individual plants and trees, why and how they found their way into a garden and which parts of these plants were used for what purpose. A purpose that over time may have gone lost and forgotten; it nevertheless helps us understand how a place evolved to what it is today.

Challenges and Opportunities in Horticulture

Challenges and Opportunities in Horticulture

By Jonathan Garner FAIH RH

What a privilege we have to work in an industry that is engaged to design, build and care for private and public sanctuaries and spaces. How rewarding does it feel to be involved with transforming an area that is often void of life, into a living and breathing ecology? How satisfying is it to steward a garden or landscape from its infancy towards maturity?

Although we’re very fortunate to work in such an industry, the challenges and difficulties with establishing a living ecology within the built environment can be numerous for the contractors who are responsible for building and planting the designer’s vision. These challenges tend to compound for the contractors who are then engaged to continually care for the vision so the landscape asset can eventually achieve the designed intent.

The current business psyche of free market economics has created both winners & losers in all industries. In today’s built environment, there is the need for being cost competitive whilst maximising profit margins & achieving deadlines. Naturally, something has to give or be compromised. Throughout most of the building industry, consumers & service providers have a level of protection provided for the quality of the finished product in the guise of standards & building codes.

To date, and according to the Office of Fair Trading, nowhere in the near future will there be any enforceable codes or standards applied to the scope of works associated with soft landscaping. Currently, local & state authorities rely on the specifications provided by landscape architects, landscape designers, horticulturists & arboriculturists. With the advent of a highly competitive market resulting in leaner design & consultancy fees, a culture of applying generic specifications for the horticultural elements within the project has become understandably, common practice.

The deregulation of building certifying has effectively bypassed local council’s authority to inspect completed projects. Most projects now engage a private certifier that generally has insufficient horticultural knowledge to determine whether the correct plants, soil preparation and other practices were put in place.

To minimise project costs, the client often deems the designer’s role is finished once the plans are handed over and the garden is built. How can design intent be assured when the client hasn’t been educated in the importance of follow up visits years down the track? How does the horticulturist receive the designers brief if they are no longer involved in the landscape asset?

The current generation of TAFE landscape graduates are appropriately skilled within the structural elements but lack sufficient understanding or possibly possess little interest in the scientific elements of Certificate 3 Horticulture (Landscape). The significant dilution of the plant based subjects in the TAFE curriculum for landscaping has created a generation of structural landscapers who, without continuing professional development or mentorship, have insufficient horticultural knowledge to determine & remedy site specific growing hinderances.

The importance of meeting the tight budget & deadline during the project can foster a culture of corner cutting that often doesn’t become evident until well after the 13-week maintenance period has ended. Many plants will survive past the 12month replacement period but may be in a state of gradual decline and are quite possibly, never likely to grow to the expected size or shape.

The design intent is further jeopardised with the arrival of the maintenance contractor nearing the end of the project. Communication is often poor between the exiting landscaper and arriving gardener. Infrastructure & irrigation locations are often a mystery as is the establishment watering schedule.

Getting trees to grow to maturity in the built environment is more challenging than most consumers think. Plants need sufficient quantities of well drained, aerated and fertile soil to mature, while a structure requires solid foundations with compacted layers to ensure integrity. Ours is the only profession that requires both of these conditions for our craft to prosper. If we fail to provide suitable growing conditions, our plants will fail. Conversely, if we fail to build on suitably stable soil, our structure will fail.

To further compound our challenges, more often than not,

  • Our fellow trades onsite have little care for, or understanding about the science of growing plants.
  • The project is well underway before we get onsite.
  • The planting areas are compacted, polluted and treated like dumping grounds.
  • The landscape budget gradually diminishes as the construction costs increase.

Often is the case that builders and civil contractors lack the understanding about how important it is to provide suitable growing conditions for our plants to fully prosper and compliment the structural asset. It is unfortunate that many trades within the building industry still see horticulture and garden construction as the work of navvies and a service that anyone can provide.

Nothing ire’s me more than seeing builders that are uneducated or ignorant to our science take on the project’s garden construction works. Although I am often engaged to advise builders with appropriate horticultural practices, I still know of very few that fully understand the importance of well-drained soil conditions and how water moves or worse still, doesn’t move through the soil.

As mentioned earlier, it concerns me even more that our TAFE courses are spending less and less time on teaching our next generation of landscape professionals, the valuable and important sciences of botany, soil chemistry and other vital subjects that are necessary for the understanding of growing plants in challenging situations such as the built environment.

As there is no evidence that our tertiary institutions will increase the learning syllabus to include the valuable and important sciences, it is left up to industry to fill the knowledge gaps. Now more than ever, is it important that industry professionals read publications and become active members within their relevant industry guilds or associations. We cannot completely rely on our learning institutions to graduate tradespersons that fully understand the complex science of horticulture in the built environment.

Diatomaceous Earth

Diatomaceous Earth

By Daniel Fuller

If you’re looking for a broad-spectrum insecticide that is residual but non-toxic, you might want to give diatomaceous earth (or D.E. for short) a go. It’s a white powdery substance made of the fossilised remains of aquatic crustaceans called diatoms.

When dry, the tiny particles are extremely sharp and are able to pierce an insect’s exoskeleton, and its desiccant properties mean that it draws moisture out of their bodies which is why it’s so effective at killing insects.


Diatomaceous earth. Image/ SprocketRocket, CC0, via Wikimedia Commons.

Sprinkle some D.E. powder on the leaves to kill leaf-sucking and chewing insects, and it will be effective as long as it’s dry. When it’s wet, it becomes completely ineffective at cutting or absorbing moisture. Another method of application is to spray the leaves with some powder dissolved in water; after the water evaporates, the leaves are left with a coating of the dried powder.

Once you’re ready to stop the effects of D.E., you can simply spray the leaves down with a hose while being mindful of where the residue ends up. Obviously, anywhere that the powder dries out will be a harmful surface for insects.

Although silica is abundant on earth, it’s rarely in a form that plants can absorb. It’s a non-essential nutrient for plants that can provide a range of benefits, including increased photosynthesis, longer roots, and increased yield. It can also help plants defend against biotic pests and diseases as well as abiotic stressors such as drought.

D.E. is a valuable source of plant-available silica that can be applied wet to the leaves and the roots with the aid of a watering can.



People with chickens will often use the powder in bedding because it keeps mites and insects away. It’s also been known to be used on mattresses that are infected with bed bugs, and the scalps of people suffering from head lice.

It’s a great natural non-selective pesticide that will kill most insects indiscriminately, so be warned that it will kill pollinating and predatory beneficial insects that come into contact with it as well.

It doesn’t harm worms and snails due to their slimy coating, although they don’t seem to like crawling over the dry powder.

The same properties that work against insects work on a much smaller scale in human and animal lungs. D.E. is not as damaging to our lungs as other hazardous materials, but just try to avoid breathing it in as much as possible.

Its absorbent and porous qualities mean that it can be used in potting mixtures, but keep in mind that as long as it’s wet it won’t be effective as a pesticide. Biogenic amorophous silica is another silica-based soil additive that is actually marketed to use as to amend soils or to include as part of a potting mix.

Although food-grade D.E. is non-toxic, keep in mind that plants need to photosynthesise so coating their leaves isn’t necessarily going to be a great long-term solution.

D.E. isn’t a magic bullet. It’s just another tool in your Integrated Pest Management (IPM) toolbox that you can use when you need to knock a pest population on the head. You’ll still need to employ other genetic, cultural, physical, and biological control methods as well.

Facing up to Dracula’s Real Intentions

Facing up to Dracula’s Real Intentions

Do you see faces in everyday objects? Our brains are heavily-oriented towards seeing patterns and shapes that help us make sense of our environment and the world around us.

Pareidolia is the term for the way we see faces in inanimate objects – like the famous face on Mars or smiling bark patterns in trees that look like a face. Researchers have found that our brains respond to perceived face shapes in objects in much the same way as we respond to real faces – assigning the same emotions and social cues as smiles, fear, surprise or warmth.

Image credit: Reddit

In the world of plants, some are much more strategic about patterns and mimicry in the pursuit of their goals – typically successful reproduction. Many plants have evolved physical and other sensory cues that enhance their ability to survive and thrive in their unique environments.
In some cases these evolutionary features also bring delight or surprise in people, and to that end they could make interesting and novel landscape features to add a dimension of emotion to your landscape.

Monkey Face Orchid. Image credit: Luis Baquero licensed under CC BY-NC-ND 2.0

Take the Monkey Face Orchid, for example – delightfully named Dracula simia, this beautiful orchid looks, to our brains, like the face of a cheeky monkey. The modified petals, known as the labellum, resemble the monkey’s mouth and make it a stunning and distinctive talking point.

However, there’s more to this flower. On closer inspection, the labellum also looks a bit like the gills of a mushroom. Researchers at the University of Oregon wanted to better understand why this orchid might resemble a mushroom when they found the orchid was frequented by tiny fruit flies that also like to eat fungi from mushrooms.

By using special 3D-printed copies of the flowers with and without scent and differing colours, the researchers established that the orchid has evolved to attract these ton flies who mistake the distinctive mushroomy smell of the labellum for fungal food sources and carry pollen between the plants.

It’s just one of many forms of biomimicry in action and more reasons to find creative joy in growing unique and distinctive plants that capture our emotions as well as offer functions to pollinators and biodiversity.

The research was published in New Phytologist in 2016: Policha, T., Davis, A., Barnadas, M., Dentinger, B.T.M., Raguso, R.A. and Roy, B.A. (2016). Disentangling visual and olfactory signals in mushroom-mimicking Dracula orchids using realistic three-dimensional printed flowers. New Phytologist, [online] 210(3), pp.1058–1071. Available at:

Cover Image credit: Neuroscience News.

Why Do We Need Pollinators?

Why Do We Need Pollinators?

By Neville Passmore FAIH RH

Most of the food crops you can think about need pollination to produce fruits or vegetables for our kitchens. The list of bee-pollinated crops is huge and if bees were not doing their job the consequences beggar the imagination.

Fruits we would not be able to enjoy include apple, citrus, plums, peach, papaya, persimmon, strawberry, avocado, chestnuts and almonds. On the vegetable front how would life be without tomatoes, celery, broccoli cabbage, onion, potato, cauliflower, zucchini and many types of beans?

Adding flavour to our cooking would be a problem without coriander, chilli, allspice, caraway, fennel and cardamom. And who could even start each day without a cup of coffee. All of this would be idle chatter if bees were not in so much strife worldwide.

Western Australia is recognised as a diversity hotspot across the globe’s Mediterranean climate areas with over 13,000 species of plants, which call the state their home. In contrast the British Isles cannot pull 2000 native species together. This local treasure chest of biodiversity is also under threat from a lack of pollinators. This enormous diversity has come about through aridity, low carbon soils and a lack of either glacial or volcanic activity to add mineral nutrients.

The relationships with pollinators include some of the most extreme and bizarre examples anywhere on the planet. Here marsupials, birds, bees, beetles, wasps, moths and even emus have a role in this reproductive task.

Why is there a lack of pollinators for our wildflowers?

Perth has lost 70% of its green cover since settlement in 1829. By 2050 it is expected we will lose a further 3%. This is habitat destruction on a huge scale. There are currently 60 local plant species classified as endangered.



What can we as home gardeners do about this?

I can see two strategies here. One is to find alternative ways to control pests. The second is to attract more birds, bees and insects to our gardens by deliberately choosing pollinator friendly plants. First up we need to fundamentally change the way we approach garden and household pests by foregoing biocides.

What is a biocide? – anything that kills life. This includes chemicals that are used to “control” insects, diseases, nematodes and weeds. Major consequences of this form of chemical warfare are many unexpected outcomes.

Neonicotinoid insecticides were developed in the 1990’s because they appeared to be safer for birds and mammals than organophosphate and carbamate insecticides, which were in common usage at that time.

Neonics as they are often called, are today the most widely used insecticides in the world. Recent reports have raised concerns that these have contributed to honey bee colony collapse disorder (CCD) a major problem for bees across the globe. Insecticides are generally indiscriminate and kill off the beneficials as well as the target insects. Bee health is affected by exposure to a wide range of agricultural pesticides.



How can we grow food and ornamental gardens without biocides?

A new approach is needed. Some alternative concepts include exclusion netting to keep pests such as cabbage moth, Mediterranean fruit fly, thrips and mites away from vegetables and fruit. Some low-tech solutions I have seen include wood ash sprinkled over cabbage plants to deter cabbage moths, coffee grounds spread around the vegetable patch to deter snails and slugs from crossing the barrier and petroleum jelly spread around the trunk of citrus trees to stop ants from spreading scale insects. The second strategy of planting pollinator friendly plants in our gardens is rich with exciting possibilities and can be approached at many levels.

I completed a revision and update of the Waterwise Plant list on behalf of the Nursery and Garden Industry of WA for the Water Corporation of WA. The online descriptions of 650 plants indicate which are attractive to birds, bees, insects, even small lizards and possums.

Beginning a pollinator friendly garden could simply consist of choosing appropriate plants from this list and planting these in your garden. Embracing this concept fully might see you developing a planting list that covers all four seasons of flowering. This is quite challenging for mid-summer and mid-winter when there are less plants in flower.

Also while it’s fine to have plenty of tree canopy cover, if there is not an understorey and ground cover, many birds will be reluctant to enter, roost or nest because the garden lacks protection and places to hide.



Natives versus exotics

In my view there is no war here, just added opportunity. Grevilleas are superstars in the bird attracting business because they are nectar producers and many species have flowers across a number of seasons. At home we have winter flowering red hot pokers and a selection of aloes that flower heavily during winter, a time when there is not much happening with local natives. Bees and nectar feeding birds constantly visit these flowers.

There is a very strong case for protecting existing native trees in urban areas. A study of one old jarrah tree in Kings Park revealed a level of visitation that is almost incredible. This one mature jarrah tree supports 83 species of native animals, birds, reptiles and insects. Not a tree but a condominium. By way of contrast wind pollinated European trees don’t have to attract wildlife to achieve pollination.

There are lots of benefits to us as gardeners from a garden filled with birds, bees, insects and native animals. We can enjoy a new soundscape and gardens come alive with movement. It’s also very comforting to know that we are helping the web of life to prosper in our suburbs. Studies have revealed that our own sense of wellbeing and mental health are considerably enhanced by contact with nature; and what better place for this but our own garden.

Neville Passmore FAIH RH is a Fellow of the Institute and former National Councillor.

Re-Vegetation or Ecological Restoration

Re-Vegetation or Ecological Restoration

By Patrick Regnault FAIH RH

As we become more environmentally conscious, individuals or communities in rural or regional areas may wish to re-vegetate part of their land to improve the local biodiversity. To be of full benefit the planting has to serve the local fauna, be a future seed bank for the local flora, and increase soil health.

Consider sourcing plant materials from different origin sites to increase the genetic potential of plant reproduction. Increasing genetic diversity has potential impacts beyond the original planting site. Dispersion by wind or animals has the potential to improve the genetic diversity in the general area.

The planting density has its importance and that will depend on your location and the type of habitat that is being created. There are no fast rules. The best way is to look at similar vegetation types and take note of the density and the range of species. By observing the connection between species we can develop a heightened understanding of how biodiversity works.

A planting that serves biodiversity requires the designer to understand the diverse roles plants play in the intricate web of lifeforms. The number of plant families is as important as the number of plant species.


Plant families have their specificity, flower shapes and seeds and a particular relationship with soil bacteria and fungi. Some families have a fleshy fruit that attract particular birds or mammals, others have a hard casing which require stronger jaws or beak. Those differences are what bring a larger range of animal species to the re-vegetated area and will lead to further plant dispersal.

Choosing a few key representatives of different families will help replicate the natural ecosystem. This extends the palette to include a diversity of plants forms and habits which creates the layers that will suit a variety of animal species. The planting has to be adapted to the soil, topography and micro-climate, which in turn may restrict or expand the range of plant selection one can use.

Diseases can be family specific. Myrtle Rust is an example of an introduced pathogen which affects the family Myrtaceae. By having a greater range of plant families represented in a planting, it is possible to mitigate plant specific pathogen diseases and increase over all biodiversity. Generalist viruses may be brought in and cause problems even in the most varied plantings.


Myrtle Rust on a Lilly Pilly. Image/ SmallBiologie via Wikimedia Commons.

However by using a variety of plant families we can mitigate the potential of diseases that can develop when we only use a limited number of families in re-vegetation work

In Eastern Australia coastal heathland the most common plant families are Proteaceae, Myrtaceae, Fabaceae, Ericaceae, Restionaceae and Cyperaceae. These 6 families are species rich and can happily form the bulk of re-vegetation. Of course further species of other plant families can be added. If the re-vegetation is using mainly Melaleuca, Babingtonia, Banksia Leptospermum and Hakea the representation of plant families shrinks dramatically. Even if it looks diverse the richness above and below ground will have been greatly reduced.


This panel shows the diversity and complex vegetation strata of a lowland rainforest. When planting habitat we have to consider the layering of vegetation to increase the chance of successful increase in biodiversity

The importance of plant – animal interactions needs to be considered if we want to successfully improve biodiversity into the future. The most effective ecological restoration happens when we design to benefit the greatest number of living species and provide stepping stones for the development of ecological communities.

Patrick Regnault FAIH RH is a Fellow of the institute and National Councillor.