How to grow grass trees from seed

How to grow grass trees: Xanthorrhoea glauca subsp. glauca at the Australian National Botanic Gardens

In this article, I show you how easy it is to grow grass trees from seed, how to identify grass tree species, and where to see them in nature in Australia.

Grass trees are unique to Australia and have a quite special role in the ecosystem. Apart from being quite unusual plants that stand out, grass trees also have a very large flowering spike that can be more than two metres tall.

This also makes them quite desirable as garden plants.

Their flowers are rich in nectar and very attractive to nectar-loving birds and insects such as honey-eaters and butterflies. In addition, they have large seed that are a favourite of seed-eating birds such as parrots.

How to grow grass trees: Grass Tree (Xanthorroea) flowering spike with ripe seed and Crimson Rosella (Platycercus elegans) eating seed
Caption left: A Red Wattle Bird (Anthochaera carunculata) feasts on honey of the Xanthorrhoea flowers.
How to grow grass trees: Grass Tree (Xanthorroea) flowering spike with ripe seed and Crimson Rosella (Platycercus elegans) eating seed
A Crimson Rosella (Platycercus elegans) enjoys a seed it has picked from the Xanthorrhoea spike.

How to grow grass trees from seed (Xanthorrhoea)

Grass trees are neither grasses nor trees, so their common name is quite misleading. This is why I prefer to use the botanical name Xanthorroea. This is the botanical name of the genus, which contains about 30 species.

In nature, grass trees are slow growing, but also get very old (350 to 450 years). However, it is very hard to transplant a grass tree from the bush, as they have unique symbiotic mycorrhizal fungi. Root disturbance upsets this symbiotic arrangement. This is the reason why grass trees transplanted from the bush often die a slow death.

For gardeners, grass trees are very desirable plants:

  • They are graceful feature plants for the garden, well-suited for wild gardens as well as formal gardens.
  • Their leafy crowns offer protection to many local insects and animals, while their flowers and seeds attract birds and butterflies.
  • They are drought hardy and do not require special care.

What is more, you can easily grow grass trees from seed. When you plant them in the garden from seedling, you will be part of their evolution and meet all wildlife they attract.

A naturally occurring local species will be best suited to your local climate (see below).

I can personally testify that you can grow a nice dense crown of grassy leaves that looks great in the garden in about 5–10 years (see below). A trunk takes many more years to develop (20+).

Collecting the seed

Many nurseries sell seed of popular Xanthorrhoea species; however, try to pick a species that is local to your area (see below).  If you are lucky enough to have a plant in the garden or in a friend’s garden, try to collect the seed after it has matured on the flowering spike.

Seed develops in capsules on the flowering spike in the months after flowering. As they mature and grow, these capsules start to stick out from the surface of the spike and are easily visible. When the capsules open, this means the seed is ready for picking.

"How

Depending on the species, there are usually 2 to 3 seeds per capsule. I usually leave most of the seed for the birds and wait until the spike naturally breaks off before collecting seed for myself.

There is usually plenty of seed left on the spike, as the seeds fit quite tightly in the capsule on the spike. You can prise the seeds out with tweezers or just tap the whole spike on a newspaper or plastic sheet until the seeds drop out.

Sowing the seed

The seeds are quite large (more than 5 mm long) and easy to handle.

"How

Seeds can be sown all year round, but spring or autumn is best, as these months have less extreme temperatures for germination. The seeds germinate well without special treatment, but not all seeds will be viable. Therefore, I have started to sow many seeds to a punnet and then pot up those that germinate when very young.

To sow:

  • Fill a seed tray with potting mix mixed with some sand to improve drainage.
  • Compress the mix and moisten.
  • Place the seeds flat (with widest part) on the surface.
  • Cover with a thin layer of soil (2–3 mm).
  • Water the seed tray again with a fine mist spray to ensure the seeds are not washed out.
  • Place the seed tray inside a transparent plastic take-away container and close the lid tightly. This will ensure moisture levels stay constant inside the container.

 

How to grow grass trees: Grass Tree (Xanthorrhoea) seed
Xanthorrhoea seeds spread out over the surface before covering with a thin layer of soil.

To ensure germination:

  • Place the seed tray in a warm (18–22°C) place in the shade and close the lid.
  • Check the seed tray regularly and add moisture if it looks like it is drying out.

Germination can occur after 4 to 6 weeks, but can take as long as 52 weeks in some species.

How to grow grass trees: Very young Grass Tree (Xanthorrhoea) seedlings in punnet.
Very young Grass Tree (Xanthorrhoea) seedlings in punnet.

About 60 days after growing grass trees from seed, I had 6 seedlings (a success rate of 1/3).

After germination:

  • Let the seedlings grow until they touch the lid of the take-away container.
  • Prick out the seedlings from the seedling tray, making sure not to damage the young root.
  • Plant each seedling in its own root-training pot using a well-draining potting mix.

"How

How to grow grass trees: Grass Tree (Xanthorrhoea) young potted seedlings
Grass Tree (Xanthorrhoea) young potted seedlings.

After potting up:

  • Grow the seedlings in pots in semi-shade for about 12 months.
  • Water the pots daily with a mist spray.
  • Check regularly if roots protrude from the bottom of the container.
  • When several roots start protruding from the bottom of the pot, carefully slip it out of the pot and do a root ball check.
  • If the root ball is well developed, wait until early spring or early autumn to plant the seedling in the garden. If it is not well developed, keep the seedling in the pot and repeat the check after a few months.

Planning and preparation

Grass trees grow slowly, but dislike being transplanted, so it is important to plan your garden design and plant them in their final spot in the garden.

Find a suitable spot in the garden that has full sun and good drainage. If your soil is clay or loam and does not drain well, create a small mound in which to plant. This will improve drainage. You can also mix some sand in the mounted soil before planting.

As the plants will remain small and not very visible for a number of years, you will have to make sure you do not accidentally step on them! So, plan to add something to remind you they are there. For example, you can plant them among small colourful plants that will not push them aside or interfere with their root system (e.g. local native perennial daisies) while they grow. You could also surround them with rocks so they are more visible in the garden.

When growing grass trees from seed, you are starting on a long but exciting journey. Over the years you will become quite wrapped and involved. What is first a small tuft of leaves, slowly grows larger and larger. Then, the plants turn into large spheres of leafy crowns and become visible and special. Next, they push up a giant spike and become a dominant part of the garden! I have now had several of these spikes, and have noticed that some of the grass trees are starting to split their crowns into double crowns. It is an ever evolving journey…

Planting

When you have found a suitable spot and are ready for planting:

  • Do a final root ball check.
  • Wait until early spring or mid-autumn when the temperatures are mild.
  • Find a suitable spot in the garden in full sun and with good drainage (not in a place where water runoff collects).
  • Dig a large hole, at three or four times as wide, and at least twice as deep, as the plant pot.
  • Water the hole and wait until it drains.
  • Carefully remove the plant from its pot and do not disturb the roots.
  • Mix some compost and slow-release fertiliser for natives into the soil you removed from the hole.
  • Place the plant in the middle of the hole, and fill the remaining space with the soil mix you just prepared.
  • Water the plant and surrounding mix well.
  • After a few days, water again with a water and seaweed solution.
  • Water every few days in hot weather, every week in cool weather for the first month(s) as needed (do not water if the soil is still wet from previous watering or rain).
  • Once you notice new leaves growing, reduce this regular watering regime and only water in hot or very hot weather until the plant is established and growing well.

Follow-up after planting

Grass trees do not need much maintenance, but need to be looked after in the first few years because they are so inconspicuous in the garden. Don’t trample them!

To look after your young plants:

  • Sprinkle a spoonful of slow-release fertiliser for native plants around the plant early each spring and autumn.
  • Water weekly until the plant is well established (in dry areas this may be for up to a year if there is little rain).
  • Once the plant is well established, it is very drought hardy and only needs watering on very hot days.

Grass trees form a symbiotic relationship in the soil with mycorrhizal fungi through their root system. These fungi are beneficial to the plants and help them take up nutrients. A tip from ABC’s Gardening Australia recommends adding a cup of brown sugar to a can of water when watering, as this will feed the mycorrhizal fungi in the soil. I have not yet tried this.

Plant growth

Your patience will be rewarded as you follow the plant’s growth over the years. I have plants of various ages in the garden and I keep adding more. This means I can show you plants at various stages in their life.

How to grow grass trees: young Grass Tree (Xanthorrhoea) plant at 5 years (shady spot)
Young grass tree at 3 years in a shady garden spot.
How to grow grass trees: young Grass Tree (Xanthorrhoea) at 7 years in semi-shaded spot
Young grass tree at 7 years in a semi-shady garden spot.
How to grow grass trees: Young Grass Tree (Xanthorrhoea) at 10 years in a sunny garden spot.
Young grass tree at 10 years in a sunny garden spot.
How to grow grass trees: Grass Tree (Xanthorrhoea) with flowering spike
Grass Tree flowering at 15–20 years in a sunny garden spot.

 

Did you know?

  • Grass trees belong to the plant genus Xanthorrhoea, which is a member of the Xanthorrhoeaceae).
  • The genus Xanthorrhoea, is endemic to Australia.

How to identify your local grass trees

The botanical name for the Grass Tree genus is Xanthorrhoea. This word is derived from the ancient Greek word xanthos, which means yellow, and rhoea, which means flowing. This ‘yellow flow’ refers to the yellow gum or resin that flows from the leaf bases in the type species, Xanthorrhoea resinosa. This resin has had multiple uses (see below).

To identify a grass tree, you need to first make yourself familiar with the botanical characteristics—and their terminology—that are common to all species. The following characteristics apply to all species of Xanthorrhoea.

Habit

All Xanthorrhoea species are woody-stemmed perennials with long, linear leaves that are crowded at the end of the stem. As they grow, many species (but not all) develop a tree-like stem, that is packed densely with old leaf bases. Some species have branched stems, each with a crown of terminal leaves. Those species that do not develop a tree-like habit have a stem that remains underground.

Giant Grass Trees (Xanthorroea glauca) with a large stem at Coolah Tops National Park, NSW.
Giant Grass Trees (Xanthorroea glauca) with a large stem at Coolah Tops National Park, NSW.

"A

Roots

The root system is quite sensitive and has a unique symbiotic relationship with mycorrhizal fungi. This is the reason why the plants dislike root disturbance and are very hard to transplant when mature.

Leaves

The long, linear leaves have a broad leaf base and a tapered end. The leaf cross-section (varying from rhombic to cuneate) at about the middle of the leaf length is sometimes used as one of the characteristics to distinguish species (see below).

Grass tree leaves are very tightly packed on the stem, which helps protect the plant during fires.

"A

Flowers

When flowering, a large cylindrical spike-like inflorescence grows from near the centre of the plant’s growing tip on a woody scape. The small flowers are bisexual and densely packed in clusters arranged in spirals on the top half or third of the scape. The flower clusters have cluster-bracts below them, and the flowers in the clusters are surrounded by small packing bracts. The characteristics of these two types of bracts are important for the identification of some species.

The flowers are strongly scented and produce sweet nectar that is loved by birds and insects. The flower perianth consists of six free segments in two whorls of three. The inner three segments are yellow to white, while the outer three are paper-like.

The stamens develop first and have flattened filaments and anthers that open by slits. The style is short at the start of flowering, but elongates as the anthers age. The ovary is 3-locular and each locule can have several ovules. There is a simple style.

Grass tree (Xanthorrhoea) cream flowers on the flowering spike, surrounded by tightly packed brown packing and cluster bracts.
Grass Tree (Xanthorrhoea) cream flowers on the flowering spike, surrounded by tightly packed brown packing and cluster bracts. You can easily see the 6 anthers in these flowers.

Fruit and seeds

The fruit is a capsule, that has an obtuse to pointed tip, and 1 or 2 seeds per locule. The seeds are mostly ovate and semi-matt black.

After flowering, the developing fruit capsules start to protrude from the surrounding persistent perianth and packing bracts on the spike. Each capsule eventually splits open to show black seeds inside.

Grass tree (Xanthorrhoea) spike with protruding, split capsules that contain the black seeds.
Grass Tree (Xanthorrhoea) spike with protruding, split capsules that contain the black seeds.

Species variation and identification

Grass trees can rarely be identified on one or two characters alone; usually a combination of many characters is required for critical determination. This means that locality is often a useful aid to identification, as not all species occur in all regions.

In the Flora of Australia, the characteristics that are useful for identification include: transverse section of the leaf at mid-length; trunk height; the ratio of the length of the scape to the length of the flowering spike; the scape diameter just below the flowering spike; and leaf colour.

The shape of the two types of bracts on the flowering spike is also used to distinguish some species from each other. When using this characteristic, only measure the largest of the bracts.

Link to the identification key to all species in Australia: Keybase, Flora of Australia

The above key is an identification key to all species in Australia. However, as not all species occur together, it is much easier to use a regional key.

In the next section, I list species by state and provide links to shorter regional identification keys for each state.

Species of grass trees in Australia

Australian distribution

Species of this genus occur in each state, but they are most abundant in a wide band along the east and south coastal areas of Australia.

The Atlas of Australian Wildlife distribution map below illustrates this.

Xanthorrhoea species distribution in Australia
Australian species distribution map of the genus Xanthorroea (Grass Tree) on the Atlas of Australian Wildlife website.

 

ACT

  • Xanthorrhoea glauca D.J.Bedford (Xanthorrhoea glauca subsp. angustifolia)

Link to species identification key for ACT: Plantnet

 

NSW

  • Xanthorrhoea acaulis
  • Xanthorrhoea arborea
  • Xanthorrhoea australis
  • Xanthorrhoea concava
  • Xanthorrhoea fulva
  • Xanthorrhoea glauca
  • Xanthorrhoea johnsonii
  • Xanthorrhoea latifolia
  • Xanthorrhoea macronema
  • Xanthorrhoea malacophylla
  • Xanthorrhoea media
  • Xanthorrhoea minor
  • Xanthorrhoea resinosa

Link to species identification key for NSW: Plantnet

 

NT

  • Xanthorrhoea thorntonii

Link to species description for NT: Wikipedia

 

Qld

  • Xanthorrhoea arborea
  • Xanthorrhoea australis
  • Xanthorrhoea fulva
  • Xanthorrhoea glauca
  • Xanthorrhoea johnsonii
  • Xanthorrhoea latifolia
  • Xanthorrhoea macronema
  • Xanthorrhoea malacophylla
  • Xanthorrhoea media
  • Xanthorrhoea pumilio
  • Xanthorrhoea sp. Cape Bedford

Link to species identification key for Qld: Keybase, Flowering Plants of Queensland

 

SA

  • Xanthorrhoea australis
  • Xanthorrhoea quadrangulata
  • Xanthorrhoea semiplana

Link to species identification key for SA: eFlora of South Australia

 

Tas

  • Xanthorrhoea arenaria
  • Xanthorrhoea australis
  • Xanthorrhoea bracteata

Link to species identification key for Tas: Keybase, Flowering plants of Tasmania

 

Vic

  • Xanthorrhaea minor
  • Xanthorrhoea australis
  • Xanthorrhoea caespitosa
  • Xanthorrhoea minor
  • Xanthorrhoea resinosa
  • Xanthorrhoea semiplana

Link to species identification key for Vic: Flora of Victoria online

 

WA

  • Xanthorrhoea acanthostachya
  • Xanthorrhoea brevistyla
  • Xanthorrhoea brunonis
  • Xanthorrhoea drummondii
  • Xanthorrhoea glauca
  • Xanthorrhoea gracilis
  • Xanthorrhoea nana
  • Xanthorrhoea platyphylla
  • Xanthorrhoea preissii
  • Xanthorrhoea sp. Lesueur
  • Xanthorrhoea thorntonii

Link to species identification key link for WA: Florabase website

 

Where to see grass trees in Australia

Grass trees occur around Australia, but are most common in the east, south and southwest (see above). They are less common in central and northern Australia. Most species occur where rainfall is more than 250 mm a year.

Here are some places I have found where you can see grass trees, organised by state:

  • Australian Capital Territory—Tidbinbilla National Park; Namadgi; Australian National Botanic Gardens
  • New South Wales—Mount Annan Botanic Gardens; Dharug National Park, Grass Tree Circuit; Royal National Park, at the junction of Curra Moors Track and the Garie Headland Track; Livingstone National Park, Grass Tree Trail; Coolah Tops National Park; Lane Cove National Park, Great North Walk
  • Northern Territory—Tnorala (Gosse Bluff) Conservation Reserve
  • Queensland—Bunya Mountains National Park; Mt Chinghee National Park; Springbrook National Park; Main Range Nationals park; Lamington National Park
  • South Australia—Arkaroola, Arid Lands Botanic Gardens
  • Tasmania—Friendly Beaches Reserve; Narawntapu National Park; Freycinet National Park
  • Victoria—Cranbourne Botanic Gardens; Royal Botanic Gardens, Melbourne; Brisbane Ranges National Park, Burchell Trail; Grampians National park, Little Desert; Gellions Run; Warby-Ovens National Park
  • Western Australia—Kings Park and Botanic Garden, Perth; Cape Arid National Park; Lesueur National Park; John Forrest National Park; Wannagarren Nature Reserve; Geraldton Sandplains/li>

There are of course many more places where you can see them.

Fire resistance

Xanthorrhoeas are resilient in fire. The fire will blacken their stems and burn off the leaves, but the leaves regrow after fire. The plants will often flower in the spring following the fire to encourage new seed production to replenish the seed bank in the soil.

Use and history of Xanthorrhoea

Aboriginal use

Aboriginal people found grass trees very useful plants and used many parts of it.

  • Flowers—The flowers are rich in nectar and this was collected with a ‘sponge’ made of stringybark and used as a food source.
  • Seeds—The seeds can be eaten and were ground to a flour.
  • Flower spikes—The flower spike is usually very straight and made of soft, light wood. It was used to make spears and also as base for fire drills to make fire.
  • Leaves—The bases of new leaves are soft and taste sweet and nutty. They were eaten. However, the tough leaves are so strong they were used as knives to cut meat.
  • Insect larvae—‘Bardi grubs’ (beetle and moth larvae) can be found at the base of the plant and were a source of food.
  • Resin—The leaf bases are packed tightly on the stem and secrete a strong, waterproof resin that holds the leaf bases tightly together. Over time, and especially as a result of fire, this resin collects at the base of the leaves on the trunk in small nodules. These nodules eventually drop to the ground. The resin nodules were used as an adhesive to fasten barbs in spears or stone axes to handles. Their waterproof characteristics also made them useful as a sealant for water containers. This meant that Xanthorrhoea resin was also a valuable trading item.
  • Roots—The roots that surround the stem base of Xanthorrhoea australis arise from an underground stem which is seasonally surrounded by sweet, succulent roots that can be eaten.

Early explorers history

The early explorers and settlers learned from the aboriginal people and soon realised some of the potentials of grass trees. They learned to eat the centre of the leafy crown and to extract the resin.

The resin was most valuable as it could be used for many purposes, such as protection on furniture and floors, and as a coating on brass instruments. Its most unusual use was in gunpowder and explosives, as it contains a considerable amount of picric acid. This unfortunately meant that they killed many grass trees.

Naming history of Xanthorrhoea

In 1770, grass trees—these strange-looking plants!—were certainly noticed by the botanists travelling with Captain Cook on HMS Endeavour, Joseph Banks and Daniel Solander.

Dr Daniel Solander used the name Acoroides resinifera as a manuscript name as early as 1770. On the UK’s Natural History Museum website, there is one watercolour on paper by Sydney Parkinson from this voyage.

Xanthorrhoea drawing by Sydney Parkinson, resulting from the 1770 HMS Endeavour voyage
Watercolour drawing on paper by Sydney Parkinson, resulting from the 1770 HMS Endeavour voyage (UK’s Natural History Museum website).

The manuscript name Acoroides resinifera was not known when the first fleet sailed to Australia in 1788 and for many years after.

According to the Australian Plant Name Index, Xanthorroea was named by J. E. Smith in 1798 (The Characters of Twenty New Genera of Plants. Transactions of the Linnean Society of London 4: 219). Smith did not cite specimens on which he based his description, but in 1818 he acknowledged he had received material from Dr John White. Thus, his description was likely based on this and possibly other material.

Dr John White was the surgeon on the Charlotte with the first fleet in 1788. He collected botanical and zoological material. In his journal ‘A Voyage to New South Wales’ about his travels, there is a colour plate that is clearly a drawing of a grass tree section. It is named the ‘Yellow Gum Tree’.

Dr White’s journal is a very interesting read and the 60 colour plates of plants and animals show how fascinated the explorers were with the new biodiversity discovered in Australia.

FREE DOWNLOAD: A Voyage to New South Wales by John White, with 60 colour plates

The State Library of New South Wales has among its images of the first fleet artwork collection two water colour drawings of a ‘Grass Tree’ or ‘Yellow Gum Tree’, citing ‘goo rung arra’ as the local native name.

Xanthorrhoea drawing
Water colour drawing of a Grass Tree (Xanthorroea)—called a Yellow Gum Tree or ‘goo rung arra’ as the local native name—in the collection of the State Library of New South Wales.
Xanthorrhoea drawing
Water colour drawing of a Grass Tree (Xanthorroea)—called a Yellow Gum Tree or ‘goo rung arra’ as the local native name—in the collection of the State Library of New South Wales.

In 1992, Nelson proposed to retain the name Xanthorroea over the earlier published name Acoroides.

There are 30 species in the genus Xanthorrhoea. These are listed by state in the section above.

Sources and resources

On this site

To find more local plant books and web sites that can help you with identification, use the Plants in the top menu, and click on the link of your state.

Other gardening articles on this site:

External sources and resources on grass trees

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Have you grown grass trees from seed? Do you have any other recommendations? Do you have any questions?

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