Grass Trees

How to choose a grass tree

The Grass Tree, Xanthorrhoea glauca, comes from eastern New South Wales and Queensland. It has blue grey foliage, forms a trunk with age and is one of the more adaptable and frost tolerant species for gardens. The Mount Lofty Grass Tree is a South Australian species from rocky hills and ranges, which also develops a trunk over time and is well suited to dry summer climates. The Tufted Grass Tree comes from South Australia and western Victoria and usually stays low, with little or no trunk, so it reads as a large tussock.

Nursery grown grass trees are raised from seed in pots. They establish far more reliably than plants dug from the wild, because their roots are intact.

Where grass trees grow

Grass trees need full sun or very light shade and sharp drainage. They are naturals for slopes, raised beds, rockeries and sandy or gravelly soil, and they handle heat, wind and dry spells once established. Poor drainage is the main cause of failure, as the roots are prone to rot in wet soil. In humid summer rainfall areas, drainage and air movement matter even more, so plant on a mound.

They look right with other Australian natives, and they fit any planting of drought tolerant plants. The flower spikes are rich in nectar and draw bees, birds and butterflies, so they earn a place among native bee plants too.

Planting and spacing

Grass trees resent root disturbance, so planting is the step to get right. Dig a hole a little wider than the pot and build the base up so the plant will sit slightly above the surrounding soil. Do not tease out or trim the roots. Cut the pot away or slide the root ball out whole, set it in place, backfill with the original soil and water in. Do not add manure or rich compost to the hole.

Allow at least a metre and a half around each plant so the skirt of foliage can spread and be seen. Mulch with gravel or coarse bark, kept clear of the base. In a pot, use a free draining native potting mix and a container with plenty of drainage holes.

Care basics

Water regularly through the first two summers, letting the soil dry a little between waterings. Once established, grass trees need watering only in extended dry weather. Avoid any fertiliser rich in phosphorus. A light dressing of a low phosphorus native fertiliser in spring is enough, and many plants grow well with none.

Growth is very slow, with the trunk gaining only a centimetre or two a year, so a trunked specimen is a plant of great age.

Common questions

How fast do grass trees grow?

Very slowly. The foliage fills out over a few years, but the trunk grows roughly one to two centimetres a year, and many plants take a decade or more to begin forming one.

Can I grow a grass tree in a pot?

Yes. They grow well in a large pot with a free draining native mix, in full sun. Do not let the pot sit in a saucer of water.

Why is my grass tree going brown?

Browning from the centre usually points to root rot from wet soil or to root disturbance at planting. Old outer leaves browning is normal.

When do grass trees flower?

Mature plants send up a tall spike of small cream flowers, mostly in spring. Flowering is irregular and is often prompted by fire in the wild.