Marin Master Gardeners
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An Aussie plant perfect for Marin gardens, too

March 05, 2011
Marybeth Kampman

A FRIEND WAS waxing poetic about the wonders of her new favorite water-wise plant, grevillea — an Australian plant that looks similar to a  bottlebrush bush. Bottlebrush bushes are quite common in Marin County; although they're nice, they're not magnificent.

She told me that to really get a flavor of the wonders of grevillea, I would need to visit Strybing Arboretum in San Francisco. They were now in bloom and could be found in the Australia section of the garden.

So I took her advice, packed up my camera and headed for the arboretum. Visiting the garden is akin to taking a virtual trip around the world of plants, since it has plants from Africa, New Zealand and, of course, Australia.

The garden has many species of grevillea, which turns out to be much different than the bottlebrush bush. The bottlebrush also hails from Australia, but it belongs to a different family of plants, the myrtaceae family. Grevillea is a member of the proteaceae family, a family of handsome and structurally beautiful plants.

Grevilleas are popular and widely cultivated in Australia. They are drought tolerant and come in a wide variety of colors, shapes, textures and sizes. The flowers occur in an inflorescence of up to 100 individual flowers. Grevilleas are often grouped together by their flower formation. Some flowers form clusters or a spiderlike flower, which can be either erect or pendent. Others form flower clusters around a terminal spike. In the toothbrush type, flowers are produced along a one-sided spike. There are
also others with flowers that form a soft feathery spike.

They are not self-pollinators; rather pollen is released before the female structure is receptive. The pollen is presented to a pollinator that transfers the pollen from one flower to another. Many of the species have flowers that produce nectar that attract birds and bees and other insects that act as pollinators. The Aborigines also enjoy the nectar of the flowers, which is shaken onto their hands and eaten directly or mixed with water to make a sweet drink. I do not recommend this, however, because some cultivated species produce small amounts of toxic cyanide.

The shrub blooms year-round, but it is at its showiest in winter and early spring. After the flowers are spent, thinly walled seedpods develop, each containing one or two seeds. It is possible to propagate grevillea from these seeds, or by cuttings or grafting. Propagation from cuttings is usually the most successful and preferred way.

Grevilleas prefer an open sunny location with well-drained soil. They prefer being planted on a slope or raised garden bed. Most grevilleas need regular watering for the first season to establish them and infrequent watering in later years. A slow deep-soaking method is recommended.

Little fertilization is required. They have a very sophisticated root system consisting of tight groupings of many small rootlets, which enables the plant to find the nutrients it needs in impoverished soils. It is often recommended not to fertilize them at all, or only with a low-phosphorus, slow-release fertilizer.

Grevilleas should be pruned regularly. Tip pruning is recommended from the time they are planted. The best time to prune is after flowering but during the warmer months. Do not hard prune during the cold months.

During my visit to Strybing I spotted a grevillea thelemanniana, which had red spiderlike flowers and is a low-growing shrub that likes sun. Another grevillea with spiderlike flower formations is grevillea lavandulacea, which has small narrow leaves and bright rose-colored flowers.

By far the showiest and largest grevillea in the collection is the royal grevillea or grevillea victoriae — a large bush covered with handsome, feltlike, bronze flower buds and beautiful deep coral blooms. The leaves are large, up to 4 inches in length, and are gray green in color, making it a wonderful addition to the garden any time of the year. The petite
grevillea rosmarinifolia is a low-growing, small, rounded shrub with spiky
leaves, similar to the leaves of the rosemary plant. The delicate pink and
cream flowers occur in clusters at the end of the branches.

At the end of the day I had become a new fan of grevillea. They would be a perfect addition to a habitat garden attracting bees and birds. The only negative attribute I discovered was that the foliage of some are known to cause skin irritations, so it's best if they're not planted where people would inadvertently come in contact with them.

For now I am quite happy to look, not touch, and enjoy their splendor.

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