Acacia : Greenhouse Plants
FF – frost free only/C – cool, minimum of 7°C (45°F)
These are the wattles or florists’ mimosa and are well worth growing for their delicate often silvery foliage and profuse bright yellow flowers mostly borne early in the year. All are easily grown from seed which surprisingly germinates better if covered with boiling water and left to soak for two days prior to sowing. This should be done in spring or early summer at 15°C (60°F). Fortunately they are fast growers and you should be rewarded with a 15-20-cm (6-8-in) tall plant in one year. Cuttings of semi hardwood with a heel will root best in June and July provided they are not kept too wet. Although plants will dislike being too damp at the roots during winter, particularly in a frost free house, it is important not to let them dry out. This is because the flower buds develop during winter and will fall without opening if this happens. I found this out to my cost with a magnificent 5-m (15-ft) specimen of Acacia armata which then took another year to flower. A. dealbata is the scented ‘Mimosa’ that most are familiar with. Dense silvery-grey leaves and stems set off the bobbles of yellow flowers that appear between December and March. A. baileyana, the Cootamunda Wattle, is sufficiently similar to make it a waste of time growing both unless the form ‘Purpurea’ is chosen. A. armata is the Kangaroo Thorn with showier flowers but less attractive foliage. These plants respond well to pruning and can either be pruned hard back, ideally after flowering, in late spring, or trimmed to keep them within bounds.