Propagation
Fresh seed should be sown in a well-drained media and the kept moist but not wet. Maintain a temperature of 18º to 21º C. (64º to 75º F) in an unheated glasshouse or open frame.
Germination occurs within 3-weeks to 3-months depending on the species, then prick-out and pot up. Careful not to over water seedlings, as they are prone to damping off and larger plants are difficult to transplant.
When removing seed from Banksia fruits it may be necessary to place the fruit in an oven for 60 minutes at a temperature of 120° C. to simulating the effect of a bushfire to opening the valves.
General pruning information
When pruning reduce only the new growth as cutting old wood is likely to cause dieback. Limbs may be removed back to the collar.
Botanic information
Leaf: The dark green leaves are linear to narrow-oblong up to 7mm (¥in) wide with an emarginate apex and a short petiole. The entire margins are slightly recurved with the upper surface glabrous and the underside white tomentose.
Flower: The small pale yellow tubulate flowers have a straight or curved pistil up to 31mm (1¥in) long. They are arranged in a terminal spike that is is up to 100mm (4in) long that appears on older wood from summer to autumn and may persist on the plant.
Fruit: The woody fruit contains up to 150 narrow elliptical follicles 17mm (µin) long and 4mm (?in) wide. They have elliptical valves that may open on maturity or require fire to release the seed. The winged seed is obovate up to 8mm (?in) long.
Cultivation
Generally, Banksia species prefer a well drained, sandy soil that is tending acidic but many species from Western Australia grow on acidic top soils with an alkaline subsoil.
When the growing Western Australian species outside their native habitat technique of building a garden bed, of acidic soil above a layer of agricultural lime commonly produces better results particularly in raised garden beds or on slopes.
During establishment, keep the soil moist but not wet and do not use fertiliser that contains phosphorus.