Buderim Garden Club

Buderim Garden Club

Banksia Spinulosa "Nana" Project

Background

To help celebrate the 70th anniversary of the Buderim Garden Club (BGC) the Club secured a $1,000 grant from The Buderim Foundation. The grant is for the purchase of around 330 potted Banksia spinulosa plants to be gifted to members and local not for profit organisations. The potted plants will then be planted out into local gardens and parks thereby sustaining the presence of this spectacular flowering native shrub in the Buderim region.

Due to the relatively large size of Banksia spinulosa the BGC Management Committee decided to purchase a dwarf form known as Banksia spinulosa ‘Nana’ which is better suited for most residential gardens.

This guide has been prepared to provide information on and to assist with the successful planting and maintenance of these plants.

Introduction

Buderim derived its name from the Hairpin Banksia which grew extensively in this area and which the Gubbi Gubbi people called “Baderram”.

The botanical name of the Hairpin Banksia is Banksia spinulosa. There are a number of species and forms of Banksia spinulosa.

Plant Description

Botanical Name: Family – Proteaceae; Genus – Banksia; Species - spinulosa; Form – Nana

Common Name: Dwarf Hairpin Banksia.

Nana is an elegant small sized evergreen shrub that can grow to a height of 1.5m and width of 1m but size can vary dependent on local conditions.

It produces a profusion of large, golden yellow flower-heads in autumn and winter.  The upright flowers are set amongst narrow, leathery, dark green leaves that provide long lasting colour through autumn and winter.  Ideal for growing under established trees.  The flowers are useful as cut flowers and are highly attractive to honey-eaters.  It is best to prune after flowering to maintain compact growth.

Nana is best grown in acidic, well drained soil in a sunny, open position.  Avoid planting in alkaline soils to prevent iron deficiency (chlorosis) that manifests as yellowing of new leaves with the preservation of green veins. This can also happen in gardens where the soil contains quantities of cement, either as landfill or building foundations, and can be treated with iron chelate or sulphate.

Planting

The best time to plant most native plants is autumn however they can be planted at any time provided appropriate care is taken e.g. protection from frosts if planted in winter.

Ensure that the potted plant has been well watered within a hour or so before planting. As this Banksia prefers a reasonably well drained soil ensure that the area where it is to be planted has been prepared accordingly. In heavy clays it is preferable to raise the height of the garden bed and/or you can improve the drainage of the soil by digging in coarse sand and organic material. If the soil is very sandy then this can be improved by digging in organic material such as compost or peat moss.

Dig a hole at least twice the width of the pot and a few centimetres deeper than the soil in the pot. If the soil is heavy clay it is better to build up the soil to a mound rather than digging a hole down into the clay as this may become a holding pit for water and the plant roots will rot. If the soil that has been dug out is heavy then improve it by mixing in some (about a 1/3 of the soil volume) coarse sand and organic material such as compost. You could also mix in a small amount (1 tsp.) of Australian native plant slow release fertiliser (low phosphorous – see section on fertilising below) to the soil removed from the hole. After tapping the plant out of the pot inspect the roots to ensure they are not “pot bound”. If there are any roots wound around the root ball then carefully straighten these out. Plant the Banksia so that the top of the potting mix is at the same level as the surrounding soil. After firming the soil around the plant give it a watering over the plant with some sea-weed solution to reduce transplant shock.

Place mulch around the plant (no deeper than 10cm) and keep it away from the trunk of the plant (5cm away). The plant should not be fertilized for at least six weeks after planting or until new growth is seen. After planting, the Banksia should be watered regularly (after the surface soil has dried out) until its roots have had time to spread. When watering, water around the drip zone of the plant and further outwards to reduce attracting the roots from neighbouring plants which will compete with the roots of the newly planted shrub. The plant should not be staked as this creates a weak, top heavy plant.

Watering

After the initial regular watering when first planted the watering frequency should be reduced and deeper watering provided to encourage deep root growth. Once established the Banksia should then be able to survive with just natural rainfall, the exception being during long dry periods.

Plant Maintenance

Once established Nana will require minimal maintenance but will benefit if you follow the below guidance.

Fertilising

While your plant can survive without feeding the application of fertiliser will improve growth and flowering. As the Banksia is a member of the Proteaceae family care must be taken when feeding as they are highly sensitive to phosphorous. If using inorganic fertilisers only use those with low (max 3-4%) phosphorous (P) levels. Organic fertilisers such as compost and aged animal manure are useful as they feed the plant over a longer duration and also assist with improving the health of your soil.

The best time to fertilise here is in August just before new growth commences. A second light application in February can also be beneficial. Apply fertiliser when the ground is moist and water in after application – during showery weather is good.

Pruning

Pruning is beneficial to most native plants and improves the appearance of the mature plant. Tip pruning can be commenced as soon as your plant is established and harder pruning, up to a third of the plant material, can be carried out when flowering has finished (mid winter). Removal of flowers for floral arrangements will also assist in shaping and thickening up the shrub.

Mulching

The application of mulch around native plants is beneficial for a number of reasons:

· minimises weed growth and therefore reduces the need to dig or disturb the soil around the roots of your plant – most native plants do not like root disturbance;

· minimises water loss from the soil;

· mulch breaks down and provides food for the plant; and

· encourages earthworms, which assist with soil structure and plant feeding.

There are many types of mulch available and each has its benefits and weaknesses. Organic sugar cane mulch and lucerne or pea straw are very good but they break down quicker than other mulches such as chipped tree material and therefore require more frequent application.

When applying mulch keep to around 10cm thick and keep mulch at least 5cm away from the trunk of the plant.