Eremophila and its Relatives - Propagation

Introduction

Most emu bushes and their relatives are propagated by cuttings or other vegetative means (such as grafting). Experience with propagation of Calamphoreus, Diocirea and Glycocystis species is limited but it can probably be assumed that similar requirements to those used for Eremophila and Myoporum could be applied.

Seed

Seeds of Eremophila are often difficult to germinate reliably and it is reported that germination is sometimes more reliable from fresh seed. However, even then germination is usually slow and can take anything from a few weeks to well over a year. Obviously, seed trays should not be discarded in haste! However, because of these problems, propagation by cuttings or grafting is preferred. Myoporum seeds usually germinate more reliably than Eremophila but again, cuttings strike readily for most species and is the preferred method.

Because of the horticultural potential of Eremophila, there has been considerable effort put into improving germination reliability of members of this genus. Several of these methods have been somewhat successful and are outlined below.

  • Extraction of Eremophila seeds from fruit

    Although it is possible to achieve germination of Eremophila seeds by sowing the fruits whole, this gives very inconsistent results. Extraction of the seeds from the fruits prior to sowing is far more effective but this is time consuming, requires considerable practice to avoid damage to the seed and, even then, reliable germination may depend on other factors such as the age of the seed, the possible presence of inhibitors and temperature. The following method of extracting seeds has been reported as being effective:

    • Thoroughly dry the fruit.
    • Place the dried fruits in a small engineer's vice (one with the metal jaws) such that either end of the nut is pressed against the jaws (use forceps to align the fruit, if necessary).
    • Tighten the vice until the nut cracks - usually the seed(s) will drop out intact.

    Extracted seed usually germinates well by conventional sowing methods in a standard seed raising mix. In some cases it has been found that removal of the testa from the seed (the thin, skin-like coating surrounding the seed) improves germination. There appears to be conflicting evidence on the influence of the age of the seed on germination.

    Further information on experiments on the germination of Eremophila seed can be found in A Study of Eremophila Seed Germination by Paul Rezl.

  • Use of smoke to assist germination of Eremophila

    The use of smoke to stimulate germination of seeds has been reported for a number of Australian plant genera. Thanks to David Booth for providing the following information regarding the use of smoked water with Eremophila.

    "Several years ago my son James (he was 15 at the time) devised a high school experiment in which he exposed these seeds to smoke (dissolved in water). Germination rates with no further treatment were around 33%.

    At the time the staff at King's Park Gardens in Perth were experimenting with smoke germination in different species, but hadn't yet got around to Eremophila. What happened was that Kingsley Dixon at King's Park was mentioned in the paper when he started experimenting with the smoke, and it was just at the time when James was looking for a science project. He had about ten different species lined up, with and without smoke, all around the verandah in hundreds of those little pots. The hardest part was sourcing seed, and some which we sent away for had zero germination, probably because it was not viable seed. But the Eremophila was a great success. Sorry I don't know which one it was. The seed had been collected by a friend who owns a wildflower nursery, on one of his trips to the Murchison over here in WA. He was glad to get rid of the useless things! He couldn't germinate them at all. He even collected emu dung to plant them in. I remember too that they came up in quick time, as no doubt they would naturally, after a fire followed by rain. He used leaf litter from the bush, mostly wattle, for the smoke."

    General information on the use of smoke to improve seed germination is available in the article Smoke Stimulates the Germination of Many Western Australian Plants (see Further Information) and from the Regen 2000 web site.

Cuttings

Most members of the Myoporum family strike readily from cuttings of hardened, current season's growth. Cuttings about 75-100 mm in length with the leaves carefully removed from the lower 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.

Grafting of Eremophila

Many eremophilas are difficult to cultivate in humid areas but, because of their ornamental potential, many people continue to make the effort. One method which is reasonably successful is the grafting of desirable species onto hardier root stocks. Experimentation into suitable stock/scion combinations is still being carried out but the best root stocks appear to be Myoporum species. M.parvifolium, M.montanum, M.insulare and M.acuminatumhave been used successfully with a large number of Eremophila scions and the procedure has certainly improved the hardiness of many of those species.

General Propagation

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


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