Veld & Flora Feature
THIS FEATURE IS FROM VELD & FLORA MARCH ISSUE 108(1), PAGES 40-43
These three succulents are new on SA’s watchlist because they seem potentially invasive. They are Mauritius hemp (above), Brazilian prickly pear cactus (top left) and spiral ginger (top right). Photos: KZN Directorate on Biodiversity Evidence/SANBI
Do your bit to protect SA’s indigenous plants by helping spot this new wave of menacing succulents.
BRAMBLE, LANTANA, BUGWEED . . .
this Terrible Trio are some of the best-known – and least-loved – plants in South Africa. They are all invasive alien plants which have established themselves in such big populations across the country that it is sadly no longer feasible to eradicate them.
Instead, we need to try to protect our surviving indigenous plants by containing them – and also by keeping ahead of the next wave of invaders.
Here we highlight the next generation’s Threatening Threesome. All three succulents highlighted here are on the watchlist at the Directorate of Biodiversity Evidence as emerging invasive alien plants.
They already show some signs of being invasive – growing in areas where they were not deliberately planted, such as along roadsides and streams. They do not yet qualify as established invasive alien plants like lantana and bugweed because their populations are relatively small and they are not distributed in too many areas.
MAURITIUS HEMP HOTSPOTS
We started tracking Mauritius hemp (Furcraea foetida) in 2010 and began control programmes from 2014. Current KZN hotspot areas with large populations of this suspect succulent are:
- South coast (Ugu municipality: towns such as Margate and Port Shepstone)
- Durban and surrounds (eThekwini municipality) inland through towns such as Westville, Kloof, Cato Ridge and Hammarsdale to Pietermaritzburg (Umgungundlovu municipality)
- North coast (iLembe municipality) and on into Tongaat, Stanger, Shakaskraal and Empangeni
Mauritius hemp has also now unfortunately been recorded in four other provinces – the Eastern Cape, Western Cape, Mpumalanga and Limpopo. We are carrying out a formal risk analysis to guide us on whether it is still possible to eradicate it from South Africa. In the meantime, it is vital to continue controlling known Mauritius hemp populations to try to prevent its spread into new areas.
Mauritian hemp produces small round, fruit-like plantlets (bulbils).
Mauritius hemp (Furcraea foetida)
This succulent is a member of the agave family – which includes the more familiar sisal or century plants – and even looks like some of them. Mauritius hemp has tall flowering stalks but a short main stem with its light green leaves arranged in a rosette – unlike some other agave, there are spaces between the leaves.
The leaf tips of Mauritian hemp often fold together into a sharp point. This leaf has small thorns on the leaf edges but this is rare.
Brazilian prickly pear cactus
Most parts of the plant have many sharp, reddish-brown spines – from the heavily branched stem to the leaves. This plant can look like a tree with its erect trunk, growing up to 20 metres high though usually less than nine metres high.
Mature ‘prickly pears’ of this cactus are about four centimetres in diameter, the size of small red sweet bell peppers. The plant appears drooping, thanks to its flattened stem pads (cladodes) that look like leaves.
The cactus has yellow, relatively small flowers.
Multiplying through underground runners means that stems of spiral ginger are densely packed together.
Like other members of the ginger family (Zingiberaceae), spiral ginger can readily resprout multiple stems from underground runners. This helps its populations survive drier winter periods.
The spiralling leaf stem is an identifying feature of spiral ginger, giving the plant its common name.
EYES WIDE OPEN
We were first alerted to another suspicious unknown plant by a member of the public who had seen it on a farm near Hluhluwe in northern KZN in mid- 2019. It was the Brazilian prickly pear cactus (Brasiliopuntia brasiliensis). Our staff also discovered more of these plants on a neighbouring property and we have tracked population sizes and extent. One population has also been reported in Limpopo. Another suspect that we were first alerted to by a concerned member of the public was spiral ginger (Costus afer). In 2019, we were warned of a small population of KZN south coast plants near Port Shepstone. The only other populations that we know about are near Westville.
Any input that you can provide will help us better understand whether or not spiral ginger is a risk in South Africa and how it typically behaves. It could be much more widespread than we know because its striking flower and eye-catching leaf arrangement make it likely that this plant is being cultivated in private gardens and/or even sold in nurseries.
Be our eyes
We are tracking these succulents at the directorate’s KZN unit because we know they occur in the province, although we also know that some of them have already been seen in other provinces. Your reports could alert us to new populations of these plants, help us assess the size of the problem that these succulents already represent and take steps to stop their spread.
Check the pictures and our identification tips and let us know if you think that you might have seen them anywhere in South Africa.
Facebook: SANBI – Biological Invasions Directorate
Reshnee Lalla (R.email@example.com) is the KZN regional co-ordinator of the Directorate on Biodiversity Evidence, which is housed in BotSoc’s partner, the South African National Biodiversity Institute (SANBI), and funded by the Department of Forestry, Fisheries and the Environment. The directorate is grateful for the support and guidance of the South African Cactus Working Group on the Brazilian prickly pear cactus project.
This article was first featured in Veld & Flora in the March 2022 edition. Veld & Flora is only available to BotSoc members.
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