Threatened Plant Species – Asclepias woodii

APOCYNACEAE: Asclepias woodii [Vulnerable]

“Local is lekker” which is why we love this month’s highlighted plant, Asclepias woodii, as it is only found in the KwaZulu-Natal midlands, and mainly centred on the town in Howick.

Asclepias woodii by Christeen Grant

Asclepias woodii are part of the Milkweed family, and they are a perennial herb. The stem is solitary, upright, up to 650 mm tall, often compressed, covered with scales or hairy scales. Leaves are usually in 4 pairs, growing upwards or almost upright, without or with short leaf stalk. Bracts are sharply pointed. Inflorescence produced in terminal pair.

Asclepias woodii flowers from November to January. Flowers 4−12, dark purple below. Leaf stalks 10−70 mm or when solitary up to 180 mm long, smooth to hairy. Corolla-lobes reflexed, spreading, egg-shaped, and pale green. Corona-lobes yellow, arising from the staminal column and equalling or slightly exceeding it, ending abruptly, rounded at the top and on the back.

It grows in unburned grassland, and it is threatened by habitat loss due to invasive alien plant infestation, frequent fires, overgrazing by livestock, and habitat loss due to plantations and development.

Photograph showing the entire plant, Asclepias woodii

If you have seen this plant, please contact Mbali Mkhize, CREW programme: KZN Node Project Assistant: m.mkhize@botanicalsociety.org.za

References:

• Brown, N.E. 1909. Flora capencis, Vol 4, 518.
• Nicholas, A. 1999. A taxonomic reassessment of the subtribe Asclepiadinae (Asclepiadaceae) in southern Africa Volume 1. PhD thesis. University of Natal, Durban

Rare Asclepias in Flower

On the regular Beacon Hill walk on the last Sunday of November, Eve Hughes was thrilled to discover eight Asclepias woodii plants in flower.  “I spotted them some distance away and wasn’t sure, but on closer investigation, Molly Perret and I were convinced.”  She called Gareth Boothway, Biodiversity Stewardship Manager for Midlands Conservancies Forum, to let him know.  He went up to see the plants and took this photo.

Asclepias woodii (Wood’s Asclepias), a member of the Milkweed family, is listed as Vulnerable in the SANBI Red Data List.  It is a  KZN Midlands endemic which reappeared on the hill recently after not being seen for nearly 100 years.

Kate Fennell, Friends of Beacon Hill committee member said “It’s always such a treat to find new things flowering on the Hill, especially a rarity such as Asclepias woodii“

This is an extract from a presentation Kate did on the plant recently:

How do Asclepiads attract pollinators?  Floral scent – Asclepiads produce a number of volatile compounds. A recent study identified between 15 – 57 compounds and a distinct scent profile for each species. Nectar is produced in small to moderate quantities.

How are the flowers adapted for pollination?   Inflorescences are dense and mechanically strong. Coronas are fat and fleshy and store nectar. Inside the cups are hairs (papilla) which are thought to secrete nectar. Pollinaria produce pollen in compact masses called pollinia. These have mechanical clips which attach them to pollinators.

What pollinates the plants? Chafer beetles. The beetles are agile, fast-flying and hairy. Importantly, they do not damage the flowers when feeding. Asclepiads with similar features share chafer pollinators. Because bees are uncommon in grasslands, chafers fulfil the role of large bees.

Join the regular Beacon Hill walk on the last Sunday of each month to see some of the 106 species of plants which flower in this special piece of grassland.

Contact Eve Hughes 082 872 4333