Spanish Moss – It’s Not Spanish And It’s Not A Moss But It Is A Biosecurity Concern..

By Gregory Lewis MAIH, Images © Gregory Lewis

Some plants attract attention because of their spectacular flowers or tasty fruit but in the case of Spanish moss we have a plant that attracts attention by literally ‘hanging around’. Read on to find out why I am not a fan of Spanish moss (well not when it’s hanging in the wrong place!).

Spanish moss (Tillandsia usneoides – also known as Old Man’s Beard) is considered attractive and desirable by a lot of people, however, there is another side to this plant that is potentially unattractive and undesirable.

Worst case scenario showing Spanish moss throughout the canopy of the same tree. Image/ © Gregory Lewis

Tillandsia usneoides is native to South America but has become naturalised in other places like the southern states of the USA. It is a member of the BROMELIACEAE family and being an Epiphyte it derives its nutritional requirements primarily from the atmosphere whilst attaching itself to the host plant via minute scales on it leaves.

It is typically used in the landscape as a plant of interest and contrast and as part of Bromeliad and Tropical plant displays. Being an old favourite of home gardeners you will often find the plant hanging off the side fence or other structure along the side of a house or attached to a piece of wood or bark. If ever there was a plant that requires minimal to no maintenance this is it! So why am I not a fan?

Well, let’s put that statement into context and that context relates purely to its impacts on trees – not how it grows in glasshouses, conservatories, shade houses or side passageways – just on our beautiful and magnificent trees!

The ease with which Spanish moss can spread is a concern. Strong winds can disseminate this plant in areas containing high numbers of mature trees that are in close proximity to one another with this type of vegetative dispersal accounting for the significant increase in its appearance amongst local tree populations. Other dispersal agents include birds and small mammals with small nesting birds having discovered how abundant and convenient the leaf strands are for nest building.

The other concern is the potentially disastrous effects caused by its continual ‘smothering and shading’. It does this by the accumulation of its long leaf strands effectively ‘overwhelming’ the host plant and inhibiting the penetration of light upon the foliage of the tree. This leads to a major reduction in photosynthesis thereby reducing the ability of the tree to convert light energy into sugars hence threatening the critical energy source needed for respiration. Stressed trees are therefore more susceptible to attack by pathogens and pests leading to an observable (and measurable) decline in the overall health and vigour of the tree.

Spanish moss inhibiting light reaching the foliage of a Norway Spruce (Picea abies). Image/ © Gregory Lewis

From personal experience trying to remove or control this plant is difficult, very difficult. Unlike other ‘garden escapees’ and woody invasive plants that can be effectively removed or controlled ‘at ground level’ (with the appropriate control method) Spanish moss being an ‘air-plant’ does its thing way above our heads! Some of the low hanging material can be removed (with time and patience) from the ground by way of a telescopic pruning pole with applicable attachment but the rest is left with no reasonable, sustainable or safe way to remove it whilst working at ground level.

Spanish moss established on a mature Turpentine tree (Syncarpia glomulifera) near the entrance to the E2 Environmental Conservation Zone Wahroonga. Image/ © Gregory Lewis

Therein lies the major concern with the spread of this plant. Once it has escaped from gardens into urban bushland and reserves it is for the most part ‘untouchable’.

A check of the NSW DPI Weed Wise website reveals that it is a listed weed where it gets a mention for being problematic on Lord Howe Island with an additional link to the National Herbarium of NSW (PlantNET).

A further check of the two LGAs that encompass where I live reveals neither Council has Spanish Moss on their respective weed lists, but refer back to the NSW DPI Weed Wise for more complete information. Both of these municipalities contain large areas of bushland and endangered ecological communities.

Eliminating or minimising the biosecurity risk of this plant will be achieved through continued consultation and co-operation by the major stakeholders’ at all managerial and operational levels.

Fortunately there are many experienced, dedicated and caring people who work within Bush Regeneration, Amenity Horticulture and Arboriculture. They have the necessary observational, practical and technical skills to reasonably reduce or eliminate this plant when it threatens parts of our urban landscapes and bushland environments by growing outside of its natural distribution. They deserve our on-going support and encouragement.

 

 

 

 

 

 

Gregory Lewis MAIH is a Horticulturist with over 40 years ‘hands-on’ experience within the horticultural industry in general and horticultural maintenance in particular.

 

 

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