It is a genus that includes numerous shrubs, sometimes even small trees, evergreens, originating from the Australian continent.
O. erubescens is a shrub, 50-60 cm tall, made up of small semi-woody stems, very branched, which bear numerous leaflets, toothed, thin and elongated, of dark green color, with the lower page covered by a thin silky hair; the shoots have leaves of a characteristic purple red color. Throughout the spring and part of summer this plant produces numerous flowers, very similar to daisies, white, pink or purple, gathered in panicles that rise a little from the foliage.
O. argophylla is a small shrub with large oval leaves, shiny and waxy, dark green, with cream-white flowers, similar to those of jasmine; O. phlogopappa has woolly shoots, which give the plant a silver-gray color, and produces numerous flowers similar to stars, white, pink, blue or purple, with a golden yellow center.
For the best development, this plant should be placed in a sunny position, or it can withstand even in a partial shade position. If it is cultivated in too shaded positions it is probable that the plant undergoes a poor flowering; this genus includes about a hundred species, many of which cannot survive in our climates, but in general the species cultivated also in Europe tolerate without problems temperatures slightly below zero; during particularly cold winters it is good to repair plants, to avoid burns due to frost and it may be useful to cover the surrounding soil with leaves and straw or mulch to protect the roots from too harsh climates.
To maintain a compact vegetation it is good to prune the plant vigorously after flowering.
From March to September, Olearia nummulariifolia should be watered regularly, leaving the soil to dry a little between one watering and another; too little watering can compromise flowering.
In the vegetative period it is useful to add to the soil of Olearia nummulariifolia a fertilizer for flowering plants to the water of the watering, every 10-15 days.
The Olearia nummulariifolia must be planted in rich and very well drained soil, possibly enriched with mature organic fertilizer lightened with sand and pumice stone, so as to guarantee the right drainage and the correct degree of humidity.
The multiplication of Olearia nummulariifolia can occur by seed at the beginning of spring; in late summer it is possible to produce semi-woody cuttings, which must be immersed in the rooting hormone before they can be placed to root in a container filled with sand and peat in equal parts; keep moist and in a shady place until rooting has taken place. The new plants obtained are planted the following year so that they can acquire the right strength to resist transplantation.
Olearia nummulariifolia: Pests and diseases
These shrubs are often subject to root rot and for this reason it is useful to check that the soil guarantees proper drainage. Before flowering it could be advisable to perform an insecticide treatment that contrasts the possible attack of scale insects and aphids.