Invasive alien species are a big problem in our country – more than you’d think and we need to do something about it urgently. The most well-known example of this is probably the chaos that the Water Hyacinth is wreaking on the Hartebeespoort Dam. Some may even surprise you, as many have been a large and common part of all of our lives.
To avoid the next ecological disaster inadvertently beginning in your garden, here is a brief introduction to the most common invasive species found in South African gardens.
There are a few species that EXTREMELY irresponsible landscapers and nurseries still grow and put into client’s gardens. One of these is still very popular, and I partly blame Pinterest for this even though the abovementioned industry professionals should know better, is Snake Grass (Equisetum hyemale).
Once planted in your garden it spreads fairly rapidly. Once established, it is a complete pain to try to get rid of and very quickly becomes a weed. It is a particular problem for wetlands, as it likes water and spreads like wildfire pushing out indigenous species.
Rather opt for the indigenous version (Equisetum ramosissimum) if you feel like you absolutely must have one.
Exotic grass species such as Fountain grass (Cenchrus setaceus), Chilean needlegrass (Nassella neesiana), Mexican feather grass (Nassella tenuissima) and serrated tussock grass (Nassella trichotoma) are a particular problem in our country because they get out of gardens very easily and ride the winds into our natural grasslands. As they don’t offer much value in terms of grazing they have a detrimental effect on the agricultural sector. Nature-based tourism is also affected in areas such as the Cape where invasive grasses displace indigenous species and affect our floral diversity.
Beautiful indigenous species to consider for your garden are Ngongoni three-awn (Aristida junciformis), Natal grass (Melinis repens), Bristle-leaved red top (Melinis nerviglumis), Buffel grass (Cenchrus ciliaris), Cape thatching reed (Elegia tectorum) and Red grass (Themeda triandra) to name a few. The environment and birds will love you for these!
Another commonly grown and planted species in gardens is the Weeping Bottlebrush tree (Callistimon / Melaleuca viminalis) from Australia. I grew up with one of these in my parent’s garden and loved it for the bees. There are a variety of dwarf varieties sold by nurseries that are a much safer option.
Black Wattle (Acacia)
The most common invasive tree in South Africa is another export from Australia, the Black Wattle (Acacia mearnsii). I know what you must be thinking, “How can an Acacia be invasive, that’s what Africa is known for”. Well, Australia “stole” the Acacia genus from us when it was found that our trees are quite different genetically. The indigenous genus of thorn trees has been renamed Vachellia and Senegalia.
Black wattle is commonly found around bodies of water and in high rainfall regions. Here they soak up as much water as possible and reproduce virulently, choking out our beautiful indigenous species.
A personal bugbear of mine is Bugweed (Solanum mauritianum). I hate this plant. You can see it all over the show, particularly the closer you get to KwaZulu-Natal, where it is devastating forests. It inhibits the growth of our indigenous species and even causes deformities in them. It smells and is a host to the KwaZulu–Natal fruit fly (a serious pest). It is also quite a health risk to humans because it is covered in fine hair that can cause asthma and allergic dermatitis.
Lanatanas (Lantana camara) were popularly used because of their striking flowers. However, it has become quite the invader, as it grows and creates dense thickets replacing indigenous flora. Secondly, it is highly toxic to people and animals, so kids need to steer well clear of it. In areas where it has replaced grazing areas, it is responsible for the death of livestock worth millions of Rands annually.
Last on today’s list is the Privets (Ligustrum lucidum, Ligustrum japonicum, Ligustrum ovalifolium). These lovely messy trees with their glossy dark green or variegated/yellow leaves are still found widely throughout South African gardens and we try to remove them in every garden we work in.
You’ll be familiar with them by the clusters of purple/black berries they produce that stain your driveways, roofs, cars and bird faeces purple. These are causing damage to our forests and riverine areas because birds love the berries and spread the seed as they go along with their day. However, don’t go snacking on the berries yourself as they are quite poisonous.
So, there you have it! A quick introduction to some of the problem children causing issues in your garden and natural environment. Please use the assistance of qualified landscapers to plant the right plants and buy them from responsible growers. Also, think twice the next time you grab a cutting or some seed from a plant you don’t know.
by Kerwyn Fourie
For more gardening advice contact Kerwyn on 064 658 2815 or email email@example.com. You can also visit the Purple Turtle Concepts and the Guild of Landscape Designers (GoLD) pages on Facebook.