October 17, 2023
The Searles Gardening Team
The word Banksia often makes us think of trees with fabulous yellow cone flowers from the Australian bush. Banksias come in many forms, from ground covers, shrubs and trees. There are over 170 species of Banksia, but the woody cones and flowers identify it as a Banksia. Banksias were named after Sir Joseph Banks, as he was the first European to collect specimens. Some species are known to live up to 100 years.
Banksias are sensitive to phosphorus in the soil. Fertilise them with a native food that is low in phosphorus. When planting a new Banksia, please do not disturb the roots when planting in the ground and grow it with Searles Native Plant Specialty Mix to avoid high phosphorus levels. If yellowing appears on many leaves, this could indicate an iron deficiency. So, apply an application of iron chelate only as stated on the packaging.
Banksias are considered a fast-growing plant and require little maintenance. Aside from regular fertilising and watering, a light prune for shaping is all they need. Banksia flower on older wood and excessive pruning will lead to fewer flowers the following season.
The majority of Banksia require well-drained soil. Heavy wet soils can lead to root rot, one of the main reasons Banksia dies in the garden. The leaves often turn brown with root rot, so check the soil is not waterlogged or overly wet. If this area is prone to waterlogging, it may be necessary to move the plant, so it is vital to check the site before planting. The Swamp Banksia or Banksia robur is a plant found in damp sandy soils. It is one of the few banksias that can adapt to a range of soils plus tolerate a part sun position. Most Banksia require a full sun position.
Banksia 'Roller Coaster' is a fast-growing ground cover that can spread to 3m. It only grows 20cm tall, so it hugs the ground and is perfect for sandy coastal areas. It has the same tremendous flowers but are smaller, plentiful yellow flowers. Banksia are excellent for bringing in bees, birds, and other native wildlife. Unfortunately, it is also attractive to caterpillars, so be ready to respond to these when you see them.
The cone-shaped flower heads are hundreds of individual flowers clustered together. The seeds are protected by the woody follicle in the centre of the flower, protecting them from damage during bushfires.
Some varieties require a fire to start the seed release to sprout and grow. It is necessary to burn the cones or heat them in an oven to start germination when propagating these varieties. Once the seed is heat treated, they are straightforward to grow.
Only a few issues cause banksia stress, wet or boggy ground, wrong fertiliser type, and caterpillars. If your garden soil is unsuitable, it can be grown in a large pot. Give them full sun and watch the bird life and bees come to them in autumn and winter when they are in flower.