Grevillea - Propagation

Introduction

Grevilleas are propagated by three principal methods; seed, cuttings and grafting. Tissue culture has also been used with a few species and cultivars but this is a more specialist method which is not of practical interest to most amateur growers. To maintain desirable characteristics of a particular plant, vegetative propagation (e.g. cuttings or grafting) must be used. This also applies to propagation of named cultivars.

Seed

As seed is shed annually, plants need to be kept under observation and seed capsules collected when they first begin to open.

Germination of seed of grevilleas can be slow and sometimes difficult. To assist germination a variety of seed pre-treatments have sometimes been attempted. Some of these work on some species but not on others.

The most usual method of pre-treatment is to 'nick' or peel off the seed coat with a sharp blade to allow moisture to reach the embryo. This needs to be done with care to avoid damage to the embryo. For seed with thin walls, pouring hot (not boiling!) water over the seed and allowing it to soak for a day or so is sometimes successful.

Seed can be sown in normal seed raising mixes and seedlings could be expected to appear in anything from 2 weeks to a year after sowing, depending on the species and the time of sowing. Those species native to temperate areas may not germinate in the heat of summer (this may be an ecological factor to enhance the chance of survival of the seedling in the wild). These species are best sown in autumn or early spring.

Cuttings

Propagation of Grevilleas from cuttings is generally a reliable method and is preferred over seed because of both the scarcity of seed and problems in germination. In addition, cutting-grown plants will usually flower at an earlier age than seedlings.

Cuttings about 75-100 mm in length with the leaves carefully removed from the lower half to two-thirds seem to be satisfactory. "Wounding" the lower stem by removing a sliver of bark and treating with a "root promoting" hormone both seem to improve the success rate. No special propagating mixes or treatments are required.

Grafting

Grevillea species native to one area of Australia may not thrive when grown in another area (this, of course, is not unique to grevilleas and is a factor to be considered with most Australian native plants). Because of this, a considerable amount of experimentation has been done, mainly by amateur growers, on grafting difficult species onto hardy root stocks. Although there is still much work to be done, the grafting of grevilleas has been most successful and is now a commonly used method by enthusiasts and is now also being used by commercial growers.

The most commonly used rootstock is the "Silky Oak", Grevillea robusta, because it is easily grown from seed and is hardy under a wide range of conditions. Another popular rootstock is the cultivar G."Poorinda Royal Mantle". It has been found that not all species are compatible with these two stock plants and further investigations are needed.

General Propagation

Further details on general plant propagation can be found at the Society's Plant Propagation Pages.


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