Banksia - Propagation

Introduction

Most banksias are propagated by seed but it is becoming more common to use vegetative propagation (eg. cuttings) to enable desirable forms and flower colours to be maintained.

Seed

Seed Removal from Follicles

  • Species with woody seed cones

    With those species where seed is retained on the mature cones, extracting the seeds usually requires heat (eg in an oven for about 1 hour at 125 degrees C). This forces the follicles to open and the seed can often be shaken out. Sometimes, however, the follicles do not open sufficiently and some additional treatment may be needed to release the seed. One method that has been successful with some species is to plunge the seed cones into cold water immediately after heating and allow them to soak for about a day. After soaking, the cones are allowed to dry in a warm, dry position where the follicles should open sufficiently to allow the seed to be shaken out or to be carefully eased out with a knife. This process can be repeated many times for those species which prove reluctant to release their seeds.

  • Species in which follicles are hidden within the spent flower clusters (the 'dryandra' group)

    With those species with woody follicles, extracting the seeds usually requires heat (eg in an oven for about 20 minutes at about 150 degrees C). This forces the follicles to open and the seed can often be shaken out. Sometimes, however, the follicles do not open sufficiently and it may be necessary to repeat the heat treatment. With species having softer follicles, the seed may be removed by cutting the follicles along the top with strong scissors, thereby enabling the two sides to be prised open.

Seed Germination

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 60 days, depending on the species. Seeds of those species from semi-alpine areas, such as B.canei and B.saxicola, require "stratification" (exposure to a period of low temperature) to enable germination to take place. One method of stratification is to place the seed on a layer of moist vermiculite or sand in a container in a refrigerator for 1-2 months before sowing.

Pre-germination of seed by sowing into a closed container containing moist vermiculite or a similar material is also a useful method of germinating seeds, particularly for winter sowing when outdoor temperatures may be unsuitable. Germination usually occurs in 1-3 weeks using this method and when the root has reached about a centimetre or so in length, the seedling can be placed into a small pot of seed raising mix.

Cuttings

Banksias which are propagated from seed may show variation in flower colour and growth habit from the original plant. In order to preserve desirable plant characteristics, propagation by cuttings is becoming more common.

Banksias are not the easiest plants to propagate by cuttings, particularly the large-leafed species, but it is certainly not impossible. 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.

Cuttings of some species may be slow to strike (6 months or more).

Grafting

Because of the difficulty of growing many Western Australian species in climates of summer rainfall (see "Cultivation"), a considerable amount of experimentation has been done, mainly by amateur growers, on grafting western species to hardier root stocks. This work has shown some success and a limited range of grafted banksias are now obtainable from specialist growers.

General Propagation

For detailed information on Banksia propagation methods, see the very detailed article The Propagation of Banksia.

Further details on general plant propagation can be found in ANPSA's Plant Propagation Pages.


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