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

Under field conditions, seeds of Eremophila germinate naturally in response to heavy rain. However, under horticultural conditions, seeds of Eremophila are often difficult to germinate and it is reported that germination is sometimes more reliable from fresh seed, although it is also known that seed will retain its viability for many years1. However, when using either fresh or older seed, 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 this is the preferred method.

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

  • Extraction of Eremophila seeds from fruit

    It is possible to achieve germination of Eremophila seeds by sowing the fruits whole, but 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, or the impact of chemical inhibitors2.

    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.

    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. Germination of seeds within whole fruits may also be improved by smoking (direct smoke, or using smoke water) but, again, yield is low.

Cuttings

Most members of the 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, e.g. IBA3000 both seem to improve the success rate.

Grafting of Eremophila

Many Eremophilas are difficult to cultivate in humid areas and/or are difficult to strike from cuttings but, because of their ornamental potential, people continue to make the effort. One method which is reasonably successful is the grafting of desirable species onto hardier root stocks. The best root stocks appear to be Myoporum species. M. parvifolium, M. montanum, M. insulare and M. acuminatum have been used successfully with a large number of Eremophila scions, as has Eremophila denticulata ssp. trisulcata. Grafting has certainly improved the hardiness of many species and has been more reliable than grafting of difficult-to-strike varieties.

General Propagation

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



Footnotes:
  1. Seed Notes for Western Australia, No. 5 - Eremophila.
  2. Richmond, G and Chinnock, R (1994): Seed germination of the Australian desert shrub Eremophila (Myoporaceae), The Botanical Review, 60(4): 485-503, October 1994.

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