The Grevillea genus has hundreds of species of shrubs and small trees, originating in Australia and New Guinea. In Europe only some species are cultivated, chosen among the most resistant to the cold. The climate of the places of origin of the grevillee cultivated in Italy is quite similar to what we could find in the central and southern areas of the peninsula, therefore with hot and dry summers, and winters not excessively cold and quite humid, but not too much. The grevillee are grown in Europe for a long time, the preferred species in European gardens are G. rosmarinifolia, and G. banksii, although the various species tend to self-hybridize with great ease, so much so as to have given rise to countless cultivars, now widespread even in nurseries. In general they are evergreen shrubs, the varieties we can find in the nursery in general do not exceed 200-250 cm in height, reaching these dimensions over the years; more often we find dwarf varieties, or however compact, which do not exceed 65-100 cm in height. They produce thin flexible, woody stems, with smooth and thin bark, often gray in color; the foliage has various forms depending on the species and variety, in the species G. rosmarinifolia remembers the rosemary leaves, therefore it has a needle-like shape, slightly fleshy; G. banksii has leaves similar to those of a maritime pine. However, there are species and varieties with deeply engraved foliage. Generally the leaves are dark green, with the lower page greyish. From late spring to late summer, they produce small tubular flowers, in shades of red and orange, combined in inflorescences of various shapes, often in long, panic cobs. The flowers of some varieties have earned this plant the name plant brush.
How to cultivate grevillee
These are fairly vigorous shrubs, which bear the drought and the summer sun well, but do not like frost; in winter they need temperatures higher than 3-4 ° C, although generally frosts of slight entity do not cause permanent damage to the plant.
So in areas with mild winters the toothbrush plant it can easily find space in the garden, in the open ground, in a very sunny place, but possibly not excessively exposed to the winds. In areas with very cold winters, where frosts are often prolonged, we grow this shrub in a pot, so that it can be moved to a protected place on arrival of winter cold. In the nursery we can find specimens of grevillea particularly resistant to cold, since often the most delicate varieties are specially grafted onto more rustic species, in order to improve their resistance to cold; in any case in doubt we cover ours toothbrush plant with agritessuto on arrival of the first cold weather.
Watering and fertilizing
The grevillee need fairly regular watering, while enduring short periods of drought; from April to September we water regularly; always waiting, however, that the soil is well dry between one watering and another. These are evergreen shrubs, which do not survive the winter if left completely dry. This problem concerns above all the specimens grown in pots, or covered with plastic material to protect them from the cold: let's remember to water them sporadically even in the middle of winter.
At the end of winter we spread at the feet of the plants some slow release granular fertilizer, in order to guarantee the right level of mineral salts in the soil for the whole summer.
In the same period we also practice a cleaning pruning, removing any branches damaged by the cold. In autumn, on the contrary, let's potter our plant toothbrush fairly vigorously, to favor the development of a dense and compact shrub.
Toothbrush Plant - Grevillea: Propagate the Grevillee
Even if grown in pots; the grevillee produce small pods, containing fertile seeds, these seeds can be sown immediately, at the time of harvesting, when the pods open or dry, we remember however that the young seedlings will be quite delicate for a few years, and will be grown in greenhouses during winter months.
From the grevillee we can also take cuttings, which generally take root with good probability.
We remove the cuttings towards the end of the summer, taking the apex of the branches that have not bloomed, or in spring, taking the apex of the branches that are not yet lignified.
From each branch we can produce more cuttings, portioning the branch into small sticks 7-10 cm long, each of which bears a few leaves.
We shorten all the leaves in the upper part of the cutting, and we remove the ones in the lower part, then we immerse the twigs in the rooting hormone and let's cross them.
The germination substrate of the cuttings must consist of a fresh, loose and very well drained soil, generally using peat soil, mixed with washed river sand.
The mixture must be kept fresh and moist until the cuttings begin to sprout; however we keep the cuttings in a cool and shaded place, in order to prevent the direct sun from quickly destroying them.