African olive (Olea europaea ssp africana)
African olive (Olea europaea ssp africana )
Tall evergreen shrub or small tree 2-15m high, with smooth grey bark, rougher at the base of large plants. New stems have small lumps called lenticels on the bark. These may be too scattered and small to be readily visible, but they can be felt by running a thumbnail up the stem. Leaves are in opposite pairs, 5-10 cm long, dark green and glossy above and paler yellow-green underneath. The yellow-green colour is produced by a dense covering of scurfy yellow scales, which can be seen with magnification. Plants growing in deep shade may have far fewer of these scales, making the leaf pale green below, not yellow-green. Flowers are tiny and white, in small clusters, followed by round green berries ripening to black.
Preferred habitat and impacts:
Apparently widely planted by early settlers, though not much used in gardens these days. It naturalises around towns and old farms. Displaces native species in remnant grassy vegetation in farming areas.
The edible olive (Olea europaea ssp europaea ) is very similar, but its leaves are white underneath, more leathery in texture and slightly down-curved at the margins. Its fruits may be oval or round, depending on the olive variety. Edible olive is also a serious environmental weed in drier parts of Australia such as around Adelaide, where it has been cultivated for a long time. It is being more widely promoted as a commercial crop now, and can be expected to become a more widespread weed in future.
The native shrubs or small trees, mock olive (Notelaea venosa and N. longifolia) have similar olive-like fruits, either black or white when ripe, but the leaves are very much bigger and broader, with a stiff leathery texture. Notelaea longifolia leaves are velvety hairy. Wallaby bush (Beyeria lasiocarpa ) has similar leaves to the olives but its fruit is a roundish capsule covered in prickly hairs. Beyeria viscosa is even more similar to olives. However, neither of these plants are very likely to be found close to towns and gardens.
One other small native shrub could be mistaken for a young olive plant. Coastal sandalwood (Santalum obtusifolium) is a straggly shrub 1-2m high with glossy leaves about 6cm long, with a white waxy underside and down-turned margins. The fruits are black, with a grape-like bloom on the skin, and a small "crater" at the top end.
Both types of olive are quite hard to kill. They will re-sprout from the base if burnt or cut down. Even with the use of herbicide in cut and paint or stem injection techniques regrowth is likely, and follow-up spraying of the new growth will be needed. Spraying is most effective on fresh new growth.
Please think very seriously before you plant edible olives. Remember that the fruits need a lot of processing before they can be used, and that if your crop is not picked, the birds will soon be spreading the seeds far and wide. They have proven extremely invasive in other parts of Australia.