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 Removal from Follicles
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.
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).
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.
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.