Eucalyptus, Corymbia and Angophora - Propagation

Introduction

Eucalypts are usually propagated from seed. Vegetative propagation (i.e. cuttings), although possible under certain circumstances (such as the use of juvenile foliage) has practical limitations and is of little interest to the average grower. Some work on grafting has been carried out in an effort to extend the range where desirable species can be grown or for early flowering of ornamental species.

Seed

   Eucalyptus seed
   Seeds (and chaff) of the River red gum
(Eucalyptus camaldulensis)
.
Photo: Brian Walters

The seed capsules need to be collected and placed in an open container in a warm position until the fine seed is released. This should occur in 2-3 days. For best results, the capsules should be at least 12 months old (ie. the most recently formed capsules are best avoided). The seed capsules usually contain true, viable seed together with a considerable quantity of infertile seed known as 'chaff'. The true seed is easily identified as it is usually larger and darker in colour than the chaff. Generally it is not necessary to separate the true seed from the chaff; both can be sown together and the chaff simply becomes part of the propagating mix.

Germination of the seed of Angophora, Corymbia and Eucalyptus species is usually quite easy by normal seed raising methods. In most cases no special pretreatment is needed, however, germination is improved with some high altitude species if the seed is "stratified" for a period of time. Stratification involves exposing the seed to a period of low temperature and is beneficial for those species normally found at high altitudes. The simplest method is to sow the seed normally in a punnet or pot, cover it and place the container in a refrigerator. The period required under stratification varies with the species and can range from 3 weeks (E.perriniana) up to 10 weeks (E.delegatensis).

A common method used for germination of eucalypts and related plants is the "bog method" where the pot containing the seeds is placed into a saucer of water until germination occurs. This results in moisture reaching the seeds by capillary action and ensures that the seeds do not dry out.

Although germination will occur right throughout the year, germination is usually slower, more uneven and percentage not as high during the period from May to mid-August. During this period germination may take from 2 to 3 weeks, compared to 3 to 10 days during spring and summer.


Bog method diagram

Grafting

A number of horticulturally desirable species are found in the south-west corner of Australia and have proven to be unreliable in humid, coastal areas of the eastern states. Species in this category include the popular "Red flowering gum" (C.ficifolia), the "Mottlecah" (E.macrocarpa) and E.caesia. All of these have large, colourful flowers and are desirable garden subjects. Grafting has shown some potential for extending the horticultural range of some of these species but the long term viability is not certain. Most work has been done on C.ficifolia using the related C.gummifera as rootstock.

General Propagation

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


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