An Australian arboreal grass

Next week, show time! I'm in London now, at Hampton Court Palace, doing what Director's should do at this stage in the build - staying out of the way.

This gives me time to talk up Australian plants, the Australian Garden at Royal Botanic Gardens Cranbourne and even a little time to talk about Australian seasons, priming the British audience for my 1 September launch of Sprinter and Sprummer: Australia's Changing Seasons.

While I do all that, here's my final plant selection from the show garden, the grass tree. We only have three individuals, all Xanthorrhoea johnsonii, a species named in honour of Lawrie Johnson, Director of Royal Botanic Gardens Sydney from 1972 to 1985.

Johnson’s Grass Tree as it's called, grows naturally in north-eastern New South Wales and up into eastern Queensland. As you'd imagine from that sub-tropical range, it would need to be tucked up indoors to survived a UK winter.

There are 28 species of Xanthorrhoea, all of them native to Australia. The trunks (above or below ground) are often blackened by fire; fire which they need to flower and set seed. They used to be called Black Boys due to their fire-blackened trunk but this name is, at the very least, disrespectful to the first inhabitants of Australia.

These days we call most of them Grass Trees because that's very much what they look like. They are in their own plant family, within an higher group (an order) called Asparagales. They are also 'monocots', like grass, lilies and asparagus.

There are some magnificent grass-trees in both Royal Botanic Gardens in Victoria (Melbourne and Cranbourne). The five multi-branched Xanthorrhoea malacophylla (native to north-eastern NSW) on the lawns of RBG Melbourne are more than a century old. All of them exceed two metres in height, something rarely achieved in the wild.

In the Australian Garden at Cranbourne there is a charming clump of grass trees off the Eucalypt Walk, on west side of the Red Sand Garden. These are the same species as in our show garden, Xanthorrhoea johnsonii.

Where I can I've highlighted culinary and other uses of the Australian flora in my four Hampton Court Flower Show posts. In this case resin in the stem and at the base of leaves makes a useful adhesive. The botanical name of the Grass Tree in fact comes from the Greek ‘xanthos’ (yellow) and ‘rheo’ (to flow), a reference to this product.

Aboriginal people across Australia use Grass Tree resin to make tools, weapons and other implements. The resin melts when heated but sets hard when cool, so it's great for cementing stone axeheads to wooden handles and spear tips to spear shafts.

Like many other nectar-rich Australian flowers, particularly those conveniently clustered closely together like banksias and bottlebrushes, the flowers of the Grass Tree can be sucked, or soaked in water to make sweet drink (which like Cider Gum sap, can be fermented).

The soft, white leaf bases and growing tip are also edible, but removing the latter will kill the plant. Given it takes many decades to get a trunk the size of the specimens in our show garden, and a century or more to get to the size of the ones in Royal Botanic Gardens Melbourne, this is not recommended.

Images: the grass trees featured are, in the order they appear, Xanthorrhoea australis (I think) near the Grampians/Gariwerd, Xanthorrhoea malacophylla on Eastern Lawn in the Royal Botanic Gardens Melbourne (taken by Jim Fogarty, featuring yours truly), and Xanthorrhoea johnsonii in the Australian Garden at Royal Botanic Garden Cranbourne.