Bugweed

My experiences with the ubiquitous Joburg pest-plant

Background info

Botanical name: Solanum mauritianum

Other common names: flannel weed, woolly nightshade (English); luisboom, groot bitterappel (Afrikaans); uBhoqo, umbanga banga (isiZulu)

Origin: South America

Why it’s a problem

Bugweed spreads very easily via seed dispersal commonly by birds. In urban areas – like Joburg – it takes hold in any unmaintained areas, like building sites, roadside verges and most worryingly in riverine areas, as well as in open areas like the few small local reserves we have dotted around. It grows very fast and therefore competes with and replaces local species.

The unripe fruits are poisonous and the hairy leaves and stems are both a skin and respiratory irritant. I personally find that handling bugweed for a length of time causes me to cough a lot, and as such I now cover my mouth and nose with a buff whenever working with it.

Bugweed is listed in our current NEMBA legislation as a Category 1b invasive species.

Controlling it

In my experience, getting rid of bugweed is a relatively easy task, but requires ongoing maintenance and follow up.
When they are very small (like the size of a hand) or even as little seedlings, they’re easy enough to pull directly out the ground as they have a taproot.
When they’re a big bigger (like when the stem is as fat as a finger) you can cut them off right at ground level using shears. If you do this in winter, they usually don’t grow back.
Once they get larger, the best route is to ring bark them. This works so well and is very easy. Simply cut into the bark (which is very easy to do) all the way around the stem at about 30-40cm above ground level and then either strip the bark off all the way down to the ground, or at minimum a 10-15cm wide strip, making sure you get all the bark off. Depending on the size of the tree, it usually dies within a couple of weeks. Then you can cut it down, or leave it to decompose naturally.
You could also choose to cut the tree down and treat the stump with chemicals, but I am not a fan of that route unless there is literally no other option. I’ve had to do this for a multi-stemmed tree recently, because it wasn’t possible to ring bark it properly, and it just kept resprouting from anywhere that got cut back.

The most important thing I’ve learnt about bugweed is that you just have to keep going back to the area to maintain it, as they are brilliant at growing back. Time and again after I’ve killed off a mature tree, I find the soil in the area littered with small seedlings the following summer – it’s as if they know that ‘mother’ died and it’s now their chance to take over. (I haven’t seen the same proliferation of seedlings around when the mature tree is still alive. I suspect some sort of chemical signal or other unknown plant magic that awakens dormant seeds.)

Catching the plants while they are young and removing them entirely is the best maintenance technique and it stops their spread very effectively as they never get to the point of flowering and fruiting. It’s definitely what’s working for me in areas I “caretake”.

Plant instead

I’ve dealt with the odd grumpy land-/home-owner when wanting to remove large bugweed trees and shrubs from outside their fences or asking them to do the same in their own (usually old and overgrown) gardens, with them citing reasons of lack of privacy or ruining their garden. I usually suggest they plant something indigenous instead.

The Invasive Species website offers a great list of indigenous alternatives for every type of invasive plant. Here are some from that list that I recommend which are suited to highveld conditions.

For a sunny position and to replace a large tree:

For a semi-shade position, and as a shrub:


References and footnotes:

*’my’ river = I live on the bank of the Sandspruit in northern Johannesburg. I have affectionately claimed the bit of it that I have access to from my house as mine. Obviously it’s not really mine, but I love it and attempt to look after it as if it were.