Banksia
Banksia are slow to establish, but they are long lived and well worth the investment of time. The upright, cone-like blooms occur across all seasons depending on the climate and variety grown. Yellow, orange, scarlet and pink blooms dominate, attracting a variety of wildlife. The distinctive seed cones remain long after the blooms have faded. Tightly-closed follicles in each cone hold large flat seeds that are only released after a long period of maturity and dryness or when naturally subjected to heat from a fire. Good drainage is required for all, but a few species, including the swamp banksia (Banksia robur) and Wallum banksia (Banksia aemula).
Look for these popular selections: –
- Pots, groundcovers and dwarf shrubs Pygmy Possum, Roller Coaster, Honey Pots, Birthday Candles
- Medium shrubs and small trees Banksia spinulosa var. collina, Heath banksia (Banksia ericifolia), Silver banksia (Banksia marginata)
- Feature trees Giant Candles, coast banksia (Banksia integrifolia), saw banksia (Banksia serrata), tropical banksia (Banksia dentata).
Growing conditions
Aspect Full sun positions are preferred. Once established, plants cope well with wind and salt spray. Choose planting sites carefully as banksia hate root disturbance. They rarely transplant successfully if you change your mind. Potted banksias are best moved during the year to positions that maximize sun exposure.
Soil Banksia cope with low soil fertility, but generally require perfect drainage (see exceptions above) and a pH of 6 – 6.5. Proteoid roots make banksia sensitive to phosphorous found in imported soil; compost, poultry manure; mushroom compost and/or potentially any fertilisers not specifically formulated for native plants. Phosphorous-induced iron deficiency (indicated by yellowing tip growth) brings about a slow, but potentially fatal decline (see Watch for).
Climate A diverse range of banksia are found in Western Australia, but they occur naturally throughout Australia, except in the wet, tropical rainforests and deserts. Take advice from staff at your local hardware or garden centre as to the most suitable species for your climate and soil type. The tough, leathery foliage allows banksia to tolerate light to medium frost and coastal exposure.
General Care
Watering Young banksia plants enjoy regular watering. Once established they are remarkably drought tolerant and only require additional watering in the very driest of times. Seasol and Seasol Super Soil Wetter & Conditioner can be applied to the soil at any time but are particularly beneficial during plant establishment.
Feeding and mulching Gardeners are more likely to kill banksia through overuse of fertilizer, rather than lack of it. You can boost the growth of young plants with an occasional application of liquid PowerFeed All Purpose including Natives. Apply a light application of PowerFeed with Troforte Plant Food All Purpose including Natives on established plants every season through the growing period or after pruning. Remember to water it in after application. Mulch plants with ac coarse mulch to keep the roots cool, suppress competing weeds and retain soil moisture when it is dry.
Pruning Tip prune young plants for the first two years to promote bushy growth. Banksia are long lasting cut flowers and harvesting blooms for use indoors may be all the pruning required on an established plant. Any other pruning undertaken should be done immediately after flowering. Mature plants that possess a well-developed lignotuber (storage organ with dormant growth buds) respond well to hard, rejuvenation pruning.
Watch for Plants in clay or other poorly drained soil tend to die from root rot. Mounding the soil, adding gypsum or other soil improvement techniques rarely improves subsurface clay sufficiently to grow banksia successfully. As plants grow the roots eventually make contact with this sub-surface clay. If you have clay soil, limit yourself to the few species that tolerate these conditions or confine plants to pots.
Yellowing tip growth typically indicates phosphorous-induced iron deficiency. Symptoms occur up to a year after plants have been exposed to phosphorous. Check the soil pH and apply Dolomite lime if below 6.5. Water iron chelates around the roots. Recovery depends on the extent of the phosphorous application; how quickly symptoms are recognised and when action is taken.
