It is a proven fact that most of our listed Alien Invasive plants have jumped the garden fence. They pose a huge threat to our environment because they displace indigenous flora; some are extremely toxic to humans and animals, while others clog up our waterways or are a fire hazard.
Gardeners sometimes accept plants as gifts from fellow gardening friends, or buy some ‘unusual’ plants at fetes or church bazaars. These new treasures may well be on the Alien Invasive list, so please check the status of the plants before you put them in your garden or pass them on to another friend. Alien invasive species are all very attractive and desirable, generally fast growing, hardy and easy to grow, and the bonus is that pests don’t like them. In other words they seem like ideal plants! There is generally a reason why these ‘unusual’ plants are not available in nurseries or garden centres; by law gifting, trading or growing Alien Invasive species is prohibited. I’m not saying all unusual plants are invaders, but it is prudent to check.
Unbeknown to me I was gifted a Cat.1a plant. I planted the little succulent (it certainly did not resemble a cacti species at all) and it grew at an alarming rate, 60 cm in 6 months! I was fooled by its lush succulent growth, but as the ’adult’ spines and leaves developed I fortunately recognised it as Austrocylindropuntia subulata.
An example of ‘escapee plants’ is in Kingfisher Creek, Steenbok Nature Reserve, where Madeira vine and Sword Fern have invaded a huge area of coastal scrub. A lot of indigenous plant material has had to be removed to get access to these invaders. Their vigorous re-growth is alarming, and complete eradication will take time and money.
Another very invasive species on Leisure Isle which originated as a gift is Equisetum hyemale (Cat 1a). It has spread into the neighbouring properties and can’t easily be controlled, because the outer surface of the stem is covered with a silica-like substance which makes it very difficult for chemical control to penetrate. It also forms stolons deep down in the earth, making manual control almost impossible.
The beautiful, sweet smelling Ipomoea alba (Cat.1a) is favoured by many gardeners. The other day I saw it growing in a friend’s garden, (the seeds came from her Johannesburg garden). It has now found a new home in a new estate in a new part of the country. Under favourable conditions this plant will spread and invade our forests and river banks.
The above examples illustrate how easy it is to unknowingly populate an area with Alien Invasive species. Let us not contribute to the misdeeds of the past! It is time for us gardeners to be more careful about what we are planting, gifting or selling; the wrong plants can have a long- lasting negative effect on the environment.
Category 1a: These are invasive species which must be controlled and where possible, eradicated. Any form of trade or planting is strictly prohibited. Officials from the Department of Environmental Affairs must be allowed access to monitor or assist with control.
Category 1b: These are established invasive species which must be controlled and wherever possible, removed and destroyed. Any form of trade or planting is strictly prohibited and landowners are obligated to control Cat.1b plants on their properties. A species management plan should be drafted for large properties.
Category 2: Invasive species regulated by area. A demarcation permit is required to import, possess, grow, breed, move, sell, buy or accept as a gift any plants listed as Category 2 plants. No permits will be issued for Cat 2 plants to exist in riparian zones
Category 3: These are invasive species that can remain in your garden. However, you cannot propagate, gift or sell these species and must control them in your garden. In riparian zones or wetlands all Category 3 plants become Category 1b plants.
All the Alien Invasive plants occurring in the Knysna area are listed on the Gardening at Leisure website: https://www.gardeningatleisure.co.za/alien-invasive-species/alien-invasive-species-knysna-area/
If you are unsure about a plant that you received as a gift, or other plants which may be suspect in your garden or neighbourhood, take a picture and send to firstname.lastname@example.org. I will assist you with the identification and give relevant information.