Australian Xanthorrhoeas

Xanthorrhoea is an Australian native plant genus. Commonly called grass trees, Xanthorrhoea plants are also known as balga grass to the Australian aborigines, which is their word for black boy. The Aborigines probably called these plants balga because after a wild fire, the bottom leaves burn away revealing a singed black trunk with long green reed like leaves extending from the top of the trunk giving the appearance of child like black figures. The Xanthorrhoea australis in the photo to the right is from the Arsia web site and shows trunks.

• Sprouting & Growing
• Species List
• On The Web

The photo on the left is a Xanthorrhoea Quadrangulata from desert-tropicals.com that is probably about 8 - 10 years old. It can take many years to expose the trunk, and that happens on larger plants by manually cutting away the bottom leaves that have turned brown, as the result of a wildfire burning them away, or by the plant growing large enough to expose the trunk beneath the leaves.

All species of Xanthorrhoea are very slow growing, but they are also very long lived -- up to 600 years! Long straight spears of white blossoms extend from the top of the tree especially in the year following wild fires. A photo of a blooming spear of Xanthorrhoea Preisii from the Missouri Botanicals web site appears below to the right.

There are many Xanthorrhoea species and subspecies from all over Australia and Tasmania as listed and described below. Generally frost tolerant, all Xanthorrhoea require well-drained soil and a sunny location because they are prone to root rot. They can be grown very successfully in pots.

Australian Aborigines

Australian Aborigines collected the resin flakes from around the base of the stalk, heated them, and rolled the resulting substance into balls. The resin would later be reheated and used to glue stone flakes to wooden spear shafts or woomeras, and to join and repair various broken implements.

Aborigines lit fires by rubbing two pieces of the dry flower stalk together, soaked the flower spikes in water to make a sweet fresh or slightly fermented drink, and used the tough seed pods as knives to cut meat or harvest insect larvae from inside the old flower stalks and the dead bases.

European Settlers

European settlers harvested the resinous gum to make varnishes and lacquers. During World War II many cans of tinned food sent to the Australian troops in the Pacific had a protective coat of grass tree varnish to keep the containers from rusting.

Native Wildlife

The spikes are packed with strongly scented flowers and attract a wide variety of insect, bird, and mammal pollinators.

Sprouting & Growing

I live in San Jose, California, where the summers are very hot and sunny and the winters have nights that go below freezing. Xanthorrhoeas work very well in my yard because they can handle these extreme conditions and are frost tolerant. Xanthorrhoea take about seven years to mature. After maturation, the plant can bloom anytime, but seems to do so more prolifically after being singed in a grass fire or exposed to smoke. The seeds are contained in a capsule which splits to scatter the seeds and germinate readily when water is applied.

A botanist from The Arboretum of Los Angeles County explains how to gather the seeds, as follows: As soon as the birds show an interest in the stalks, gather them gently, cut them into lengths and put them into paper supermarket bags. Do not put them in plastic bags, they will mildew. Let them dry, and then beat on the bag with a broom stick. Take out the stocks and the seeds will be in the bottom of the bag.

If you want to leave the stalks on the plant - because they look really cool - just wait until the pods open on the stalk and the small black seed looks like it's getting ready to fall out. Use a small tweezers or your fingers to gently remove the seed (be careful not to damage it!). If you let the stock and open pods dry out over a few weeks, you can remove the pod with your fingers and then remove the seed from the pod. You can also shake the stalk and the seeds will tumble out. Have something below to catch the seeds. I found that cobwebs work really well for catching the seeds that fall.

Xanthorrhoea australis will sprout in regular potting soil. I use an organic one that comes from my local nursery. Place the seed about 1/8 to 1/4 inch below the surface and cover with a thin layer of sand (about 1/8 inch). The sand forms a permeable layer through which to water without disrupting the seed below. I've found that without the sand, it can be too easy for the seed to float to the top of the soil when I water, and then it does not sprout. Although, if you do it without sand, you can just push the seed deeper into the soil - up to an inch - and they still sprout.

It can take 6-7 weeks to see the first sprout, although I've seen some sprout in 2-1/2 weeks. The photo on the right is a brand new sprout. It is not unusual for the black seed to stay on the tip for a few days or weeks. It eventually drops off.

Growers from the Windmill Outback Nursery use 50% sand with 50% perlite and place the seed about 1/4 inch below the surface. With this method, once the seed sprouts it should be moved to potting soil with perlite (about 50% each) because it will need nutrition from the soil to grow. The photo on the right shows a sprout that has started to divide.

Another method I'm trying that I learned from the Australian Native Plants nursery is three parts Perlite to one part peat with a light covering of washed sand twice the thickness of the seed. Drench the seed with a fungicide after sowing to prevent "damping off."

Unsprouted seeds should be kept moist but not wet. Once they sprout, keep them moist but be careful not to over water. They grow very, very slowly and do well in containers. Once established, they can live 600 years.

To learn more, read these interesting and detailed notes from John Summerfield in Western Australia.

Species List

The Xanthorrhoea genus is part of the Xanthorrhoeaceae family, which is made up of small trees or perennials with woody stems. The leaves are tough and linear, and the flowers are radially symmetrical, bisexual, and look like spikes. The seeds are individually contained within capsules. The following is a list of known Xanthorrhoea species and subspecies with a brief description of some.

Acanthostachya

Xanthorrhoea Acanthostachya, sometimes spelled Acanthostachys, is from South Australia. It is also known as spiky grasstree. It has a short trunk with one or sometimes two crowns. The leaves are a grey green and are somewhat shorter than other species reaching up to 70 centimeters in length. The flower spike is prickly and either purple green or green and is between 50 centimeters and one meter long with white flowers that appear between August and November.

Australis

Xanthorrhoea australis is native to South Australia, and is also known as the Australian Grass Tree or Kangaroo Tail. It has very long, thin, grass-like leaves up to 3 feet and is generally found along the rocky hills of Southeastern Australia. It takes 30 years or more for the leaf tuft to rise above the trunk.

Gracilis

Xanthorrhoea Gracilis is also known as the Slender Blackboy and does not form a trunk. It is native to Dwellingup West Australia where the annual rainfall is 34 inches. It grows best in sandy gravel soil.

Macronema

Xanthorrhoea macronema is tufted and trunkless with many flexible linear leaves that are about 1 meter long and rise from the ground. The cream flower spike has a 1-1.5 meter stem, and the spike varies in length from 5 to 13 centimeters. From a distance the flower spike resembles a banksia flower. It flowers in spring to summer and is found in Queensland and New South Wales. The seed germinates in about 5 weeks.

Minor

Xanthorrhoea minor is small with a slender scape. It is widespread on poor sandy soils and native to Tasmania.

Media

Xanthorrhoea Media is a small species with a slender stem.

Preisii

Xanthorrhoea Preisii is from Western Australia and is also known as the Western Blackboy. It has an upright or slightly twisted trunk that can reach 20 feet at maturity. It likes sand, sandy loam, loam or gravel soils. The one in the photo above on the right opposite the bullet list is about 4 or 5 years old.

Quadrangulata

Xanthorrhoea Quadrangulata also known as the rock grass tree or Mount Lofty grass tree is from South Australia. It has four-sided leaves, gets up to 6 feet high with flower spikes that get up 15 feet tall. The photo at the very top-left of this page is Xanthorrhoea Quandrangulata taken from Desert-Tropicals.com.

Resinosa

Xanthorrhoea resinosa has no trunk and a scape longer than the spike. The leaves are 2-6 millimeters wide. It grows near coastal New South Wales to East Gippsland.

Semiplana

Xanthorrhoea semiplana is almost trunkless with leaves to 1 centimeter wide and flat on one side. They grow primarily in the Mt Lofty Range area.

Semiplana Tateana

Xanthorrhoea tateana has a trunk that is 1-4 meters and leaves like Xanthorrhoea semiplana, and grows on Kangaroo Island.

Thorntonii

Xanthorrhoea Thorntonii is also known as Cundeelee Blackboy. It is a robust form of the desert blackboy.

On the Web

The following websites and books have contributed to the information on this site by way of photographs or information, or can provide more information on or access to Xanthorrhoea plants.

• Chiltern Seeds
• B & T World Seeds
• Desert-Tropicals.com.
• Missouri Botanical Gardens.
• Australian Native Plants Nursery.
• The Arboretum of Los Angeles County.
• Windmill Outback Nursery.
• Native Trees and Shrubs of South-Eastern Australia, by Leo Costermans.
• Australia Native Plants, John W. Wrigley, 4th Edition, by Murray Fagg.