Grass trees

Grass trees grow very slowly, approximately 1 cm per year. A plant, which is harvested from its natural habitat at a height of 2 metres, can be anywhere between 100 to 200 years old, depending on prevailing conditions and climate. Grass trees form part of Australia’s hard-leaved, fire adapted vegetation and occur mainly on soils which are very free draining, and consequently low in nutrients. They have a wide and relatively shallow root system, about 600 mm deep and up to about a metre wide.

Cultivation

Choose a plant which has healthy, dark green foliage and select your planting site carefully. Tie the leaves of the plant into a bunch using soft cord before transporting or planting as the end of each leaf is quite sharp and you will find it much easier to deal with the plant if the leaves are confined.
Grass trees need to be in full sun. They require very free draining soil and an open position with good air circulation. If you can’t provide these conditions in the garden, then it may be best to transplant the grass tree into a suitable container.
If planting into the ground, the planting hole must be prepared before you remove the grass tree from the container. The hole should be wider, and deeper than the container, this will allow room to incorporate a mixture of coarse sand, gravel and some of the existing soil below and around the root ball of the plant. The grass tree should be planted at the same depth as it was in the container.
If the planting area does not have good drainage it will be necessary to raise the bed by about 50cm.
Do NOT tease out the roots when the plant is removed from its container. It is important that the roots are disturbed as little as possible.
Do NOT put any fertiliser in the planting hole, or around the plant.
If planting into a container, use a good quality, free draining mix, such as ‘native’ potting mix. The container should be quite wide and will need to be up, off the ground, on pot feet or bricks, so that the drainage holes in the pot remain clear. You may also need to drill extra drainage holes in the pot.
Water in well after planting to remove any air pockets in the soil, and apply ‘Seasol’ at the recommended rate. 'Seasol’ is a liquid plant tonic which encourages root growth. Continue to apply ‘Seasol’ at 2 weekly intervals for a couple of months.
The plant will require small amounts of water frequently for about the first month after planting. After the first month, watering should be reduced to about once a week during the warmer months.
It is not really necessary to fertilise grass trees but if you wish to do so, then once a year is sufficient, using a fertiliser for native plants.

Grass trees can be rejuvenated by fire, but this can only be done every 5 years as this process consumes the stored reserves of the plant. After burning a plant may take between 3 to 6 months to develop new foliage. Grass trees sometimes appear to flower after a fire but this is not always the case. Each species of grass tree will flower only at a particular time of year, and only if they have sufficient stored reserves to do so.
Grass trees also flower as a reaction to stress.

Pests & Diseases

Phytophthora cinnamoni – this is a fungal disease which causes root rot. Usually present in damp or poorly drained areas. Grass trees are quite susceptible to this problem.
Scale on foliage – treat with pest oil or white oil when conditions are cool.

Ann Costelloe