Leptospermum and its Relatives - Propagation

Introduction

Plants in the Leptospermum Alliance are propagated by both seed and cuttings, the best method for a particular species being determined through experience. Grafting may be a possibility for those species that have proven to be difficult in cultivation.

Seed

Seed of the plants in the Leptospermum Alliance is either retained within the mature fruits until the plant dies or is released from the fruits annually. Whether seed is retained or released is mainly determined by environmental issues - plants native to areas frequented by bushfires usually retain the seed on the plant.

   Callistemon seed
   The seed of members of the Leptospermum Alliance is very fine - there is enough seed from these Callistemon capsules to produce a forest! Photo: Brian Walters

In the case of species which retain the seed indefinitely on the plant, the capsules need to collected and placed in an open container in a warm position until the fine seed is released. This should occur in 2-7 days. For best results, the capsules should be at least 12 months old (ie. the most recently formed capsules are best avoided as the seed may not be fully developed). With those species which release the ripe seed annually, the plant needs to be kept under observation and seed capsules collected when the capsules commence to open.

In some cases (eg. Beaufortia), seed may not be released even after the mature capsules have been removed from the plant. In such cases it has been found that grinding the capsules for a few seconds in a coffee grinder (and then sowing the debris) is an effective treatment method.

Seed usually germinates well by conventional sowing methods in seed raising mixes although seedlings may be subject to "damping off". To minimize this possibility, keep seeds moist but not wet. Germination should occur in 14 to 30 days, depending on the species.

A common method used for germination of Callistemon 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.


Bog Method Diagram

Cuttings

Propagation of members of the Leptospermum Alliance from cuttings is generally a reliable method. 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.

Grafting

Species native to one area of Australia may not thrive when grown in another area (this, of course, is not unique to this group of plants and is a factor to be considered with most Australian native plants). Because of this, some experimentation has been done, mainly by amateur growers, on grafting difficult species onto hardy root stocks, however, little data is available on successful scion/stock combination.

The following table lists suggested stock plants that could be considered for some of the difficult to grow species. The species selected as a stock should, of course, be a reliable grower in the district when the grafted plant is to be grown.

ScionPotential Stock Plant
BeaufortiaCalothamnus, Melaleuca
EremaeaCalothamnus, Melaleuca
Western KunzeaEastern Kunzea
Western MelaleucaEastern Melaleuca
PhymatocarpusCalothamnus, Melaleuca
RegeliaCalothamnus, Melaleuca

General Propagation

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


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