ROCK WATTLE

(Acacia rupicola)

(Photos: C. Schultz; Rapid Bay)

There are lots of prickly wattles; you are probably used to seeing one called Acacia paradoxa (Kangaroo Thorn). This is another prickly one, also with ball-shaped yellow flowers on short stems from the leaf base. However, whereas Acacia paradoxa has thorns growing from the leaf bases, it is the leaves themselves that are prickly on Acacia rupicola, the rock wattle: there is a sharp point at each leaf tip. Those leaves are lance-shaped, about 10 times as long as they are wide: 2.5cm to 2.5mm! The shrub itself grows to about 2-2.5m, is rigid and glabrous (smooth). Young growth can be a bit sticky, and the bush can have a smell of resin. The books say flowers finish in November, so the long curved brown seed pods should be visible in January. Nature doesn’t always read the books – these photos at Rapid Bay mid December had both flowers and ripe seedpods. Don’t get stabbed by those leaves when harvesting seed, and look carefully for insect life! This well camouflaged orb- weaver is the same colour as the dying flowers.

SALTY ICE PLANT

(Mesembryanthemum crystallinum)

 (Photos E. Cousins, Cape Jervis; young plant, close up of leaf, flowering plant showing summer stress)

We have featured this weed before, but a recent posting of its picture on SA Natureteers with a request for identification prompted us to revisit it. The response to the posting from many readers was immediate: GET RID OF IT! The Diggers Club^[1] states this plant “may naturalise in coastal areas” and “Not for SA”…and anyone who wanders around Cape Jervis over winter-summer can see why! This annual herb is a prostrate succulent, about 10 cm high.  Its leaves are covered in large glistening lumps, or bladder cells of water, giving the plant its common name. The plant grows rapidly over winter, but its growth slows in spring. Dry summers can kill the plants, but by then, its seeds have probably already been spread by rabbits (who eat them). Ice plants have several characteristics which make life hard for their neighbours: they can absorb a lot of moisture from the soil, outcompeting most other species; high levels of nitrate which build up under the plants can be harmful to other species; salt accumulates in the plant over its lifetime, and this is then released into the soil when the plant dies back in summer. Less salt-tolerant species suffer because of the salt which can inhibit both grown and germination of native species.

^[1] https://www.diggers.com.au/shop/edibles/salty-ice-plant/s601/