GREENGOLD GARDEN CONCEPTS
CARE AND MAINTENANCE NOTES

BANKSIAS

They first became known to Europeans in 1770 when James Cook landed at Botany Bay with Joseph Banks and Daniel Solander who were astounded at the very remarkable plants they found.

Four Banksia species were collected there and another at the Endeavour River at Cooktown.

Most of the specimens which Banks and Solander collected are now in the British Museum but a few are held by the herbaria of the Royal Botanic Gardens at Sydney and Melbourne.

Banksia was given its botanical name in 1798 by the Swedish botanist, Carl Linnaeus, in honour of Joseph Banks's discovery of the genus and his great contribution to botanical collection.

There are about 73 species, all found only in Australia except B. dentata which is also found in New Guinea. The majority occur in the southern regions of Western Australia, with only fourteen natural to the eastern side of the continent. Some are found in a wide area while others are very restricted in their location.

Banksias are woody, evergreen plants, ranging in habit from prostrate shrubs to tall trees. Their rugged appearance is one of their best known features. The tree forms usually have a single trunk, rough and gnarled. The shrubs often have many stems and erect flowers at ground level.

About half the Banksia species have a fire-resistant trunk or woody stock, called a lignotuber, from which they re-shoot after a fire, and bark 1 cm thick. The others have thin bark and stems which are killed by fire. These regenerate from seed but take several years to reach fruiting stage again.

There is a great variety in the leaf or foliage of Banksias. They are usually hard or leathery, generally toothed or lobed. They can be small and heath-like, such as B. ericifolia, or large with varying depth of division and tooth pattern. The arrangement is mostly alternate or crowded into whorls.

The underside is conspicuously white or silvery in some species while a number of species have attractive colourful new foliage, sometimes velvety, in tones of white to pink to brown.

Banksias produce their flowers in dense spikes, often large, with hundreds or thousands of individual flowers arranged in a very complex pattern. The shape of this inflorescence varies from spherical or globular to long and cylindrical.

Many flowerheads are creamy yellow but there are many other colours and combinations of colours from bronze to vivid orange to bright scarlet and even purplish black and purplish green, B. praemorsa.

Banksias in bloom produce a sweet nectar or "honey" which insects and birds love. This is the source of the old name "Native Honeysuckle". Most banksias flower from late summer to winter.

As the flowers wither the spikes develop into a fruiting "nut" or cone, made up of woody follicles which are velvety when young.

They take from 1 to 2 years to develop depending on the type. Only a few flowers produce seed. The follicle splits to release two winced seeds. Under natural conditions they may remain on Some trees for years.

Many species need heat, not just drying, to remove the seed. Place the fruit in a very hot oven for 5 to 10 minutes or douse the fruit with methylated spirits and set it alight. The fruiting cone is one of the most fascinating features of Banksias such as B: laricina, rose-fruited banksla, and B. candolleana -duck's bill.

CULTIVATION OF BANKSIAS

Banksias are usually grown from seed or from cuttings from plants raised from seed from the wild. Sow seeds in spring or autumn to avoid temperature extremes. Place them in a well-drained medium such as sand or sand and perlite or vermiculite with the wing uppermost.

Cover lightly with soil - a slightly acid one is best. Germination should occur within 3 to 6 weeks. Pot the seedlings on within a few weeks to avoid roots becoming pot-bound. Watch for "damping off" in the early stages.

CARING FOR BANKSIAS

Banksias are used to well-drained soils with poor nutrient levels. Do not plant in heavy or clay soils without first adding gypsum or other soil conditioner or by raising the growing level by at least 30-60 cm. Water only when really necessary. Fertilizing should be minimal. They do not like phosphorous. A slow release low phosphorous treatment is best. If leaves yellow use chelated iron according to the instructions. Avoid organic mulches which increase the nutrient level. A groundcover mulch creeper such as a Kennedya sp. is much better. Do not prune heavily, otherwise Banksia may not continue to grow.

CHOOSING BANKSIAS

Some of the most showy Benksias are those from WA which are difficult to grow in the Sydney region. Some species may be available, grafted on to fungal-resistant eastern species.

If you want to grow Banksias, and every garden should have them, start with EASTERN SPECIES. As your knowledge and experience grows, you can-then experiment with other more difficult types.

Banksia serrata. "serrata" saw-edged referring to the leaf margins. Occurs in near coastal regions from Old to Tas. 10 to 12 m high. Large flower spikes summer-autumn, grey-green in bud, turning yellow. Large woody cones outstanding. slow growing but long lived. Especially good for exposed coastal sites and"as a sand binder. A prostrate form known as B. "Pygmy Possum" is available. Banksia aemula is similar but leaves are smaller and flowers brighter. Its fruit is the "Big Bad Banksia Man" of May Gibbs' stories.

B. robur grows in sand or peaty sand in Old and NSW. Spreading shrub with number of stems to 2m. It has large, leathery leaves with coarse margins. New growth is brownish with a dense felt-like covering of brown hairs. Stunning large flower spikes, green in bud, becoming cream-green. Likes moisture.

Banksia oblongifolia used to be known as B. asplenifolia. Grows from Qld to Ulladulla, NSW, mostly near the coast on moist sites. A 2- 3m spreading shrub. Very attractive garden shrub with velvety brown new growth on foliage and greenish-yellow flowers. Best in moist soil in sun or partial shade. Slow. B. paludosa is related. From central NSW in coast and mountains. "paludosa" means "marshy". A compact shrub to Im x 1.5m. Does best in sunny position. Can be pruned to shape. Worth looking for.

Banksia integrifolia ranges from small shrub to tall tree on coastal sites from Qld to Vic. "integer" means "entire" - the adult leaves do not usually have the serrations of other species. Grows on heavy or light soils on both coast and tablelands.

A prostrate form is successful.

B. ericifolia is "heath-leaved" From central coast and ranges of NSW especially on sandstone. A strong growing bushy shrub with long yellow to orange spikes often with black or red styles. Very attractive to birds. A good garden specimen.

B. spinulosa, Hairpin Banksia. A showy shrub 1-3 m by 1-2m, with long, narrow leaves. Flowers over a long period with spikes from yellow to orange. Good winter colour. Will grow from seed or cuttings. Banksia "Giant Candles" is an excellent garden plant - believed to be a hybrid between B. ericifolia and B. spinulosa.

Of all banksias, Banksia marginata is the most widespread, from Qld through to Tas and SA in varying size from a 1 m shrub to a 12 m tree. "marginata" refers to rolled-under leaf margins. Leaf form is very variable. Flower spikes are small -from green to bright yellow. Easy to grow in all situations. Good for screening or windbreak. A prostrate form is sold.

A rare species, B. conferta var. penicillata, from Blue Mts also makes an excellent garden plant. Another form is found in Qld. Two mountain species, B. canei from south-eastern NSW and eastern Vic, and the related B. saxicola from the Grampians, are well worth trying, especially B. canei "Celia Rosser"