Xanthorrhoea australis — an easy houseplant
SPECIMEN · FROM THE LIBRARY
Xanthorrhoea australis

Xanthorrhoea Australis

Updated · 117 observations
ON THIS PLANT

Xanthorrhoea australis, the grass tree, austral grasstree or blackboy, is an Australian plant. It is the most commonly seen species of the genus Xanthorrhoea. Its trunk can grow up to several metres tall and is often branched. In certain Aboriginal languages, it is called bukkup, baggup or kawee.

A note from PlantMom

The Austral grass tree is fairly disease-resistant and is generally not susceptible to illnesses. In terms of care, this plant is fairly low-maintenance. When grown outdoors it needs only minimal watering, and larger specimens usually do not require pruning. Smaller plants, however, should be pruned after they have finished blooming. The Austral grass tree is suitable for anyone with an outdoor area, such as a garden or a deck, and does not demand extensive plant-care experience.

— PlantMom
CARE GUIDE

How to keep Xanthorrhoea Australis.

Water

The Austral grass tree is a drought-tolerant plant well-suited to the arid conditions of Australia. It thrives with minimal moisture, needing water only once every three weeks. To avoid root rot, this plant prefers well-draining soil that mimics its natural habitat. This type of soil supports its growth cycle in outdoor, non-tropical climates.

Temperature

Austral grass tree is naturally adapted to environments between 68 to 100 °F (20 to 38 ℃). It does best within this range, and adaptation to extreme temperatures may be necessary with seasonal changes.

Fertilizer

Fertilizing an Austral grass tree is best done in early spring when it comes out of dormancy. This promotes overall growth and flower development. Fertilizer improves the foliage, stems, and branches, and encourages flowers that are larger, more vibrant, and longer-lasting. It also helps move nutrients from the roots to the flowers and enhances the plant’s health and resistance to disease.

Pruning

The Austral grass tree benefits from pruning between early and late winter. To promote healthy growth, remove old flower spikes and dead foliage, but be careful to avoid cutting into the crown. Regular pruning not only stimulates growth but also reduces the risk of fire by eliminating dry leaves. Always use clean tools to prevent the spread of disease.

Pot & Repot

When repotting an Austral grass tree, select a pot 1–2 inches (2.5–5.1 cm) larger with good drainage. Use a well-draining potting mix. Repot in spring or fall, making sure the root ball sits slightly lower than the rim of the flower pot. Water thoroughly after repotting and place it in a warm spot with indirect sunlight.

CHARACTERISTICS

Botanical profile.

Plant Type
Shrub
Life Cycle
Perennial
Genus
Xanthorrhoea
Family
Asphodelaceae
Hardiness Zone
9-11
Mature Height
0.91 m to 3.66 m
Mature Spread
1.22 m to 1.83 m
Leaf Color
Dark Green
Leaf Type
Evergreen
Flower Color
White
Flower Size
2.54 cm
Bloom Time
Early fall, Mid fall
Planting Time
Spring, Summer, Autumn, Winter
Harvest Time
Late fall, Early winter
ALSO KNOWN AS

Other names.

en Austral grass tree en Grass Tree
FREQUENTLY ASKED

Reader questions.

How should I water my Austral grass tree?

Your Austral grass tree does not have specific requirements for watering. You can use various common watering tools like watering cans, hoses, or even cups. To water the plant, it is recommended to pour the water directly onto the soil. Make sure to evenly moisten all areas of the soil to ensure all parts of the root system receive water. Using filtered water is better than tap water as tap water may contain harmful particles for plants. Similarly, it is preferable to use water at or slightly above room temperature, as very cold or hot water may shock the Austral grass tree. However, the plant generally responds well to any type of water you provide.

Why should I put fertilizer on my Austral grass tree?

The Austral grass tree requires regular fertilization because its showy leaves require a significant amount of energy to produce and maintain. However, it also needs to allocate energy for the growth of its stems, branches, roots, and other vital structures. If you neglect fertilization, two likely outcomes may occur. First, the leaves may lose their natural color and texture, resulting in an overall unhealthy appearance that significantly diminishes its ornamental appeal. Second, the tree's growth may slow down or produce weak growth that is more susceptible to breakage.

What are the sunlight requirements for the Austral grass tree?

The Austral grass tree thrives best in full sun, which means it requires above 6 hours of sunlight daily to ensure healthy growth. However, it can also tolerate partial sun, needing about 3-6 hours of sunlight. It's crucial to watch how sunlight moves through your garden, selecting spots that offer a perfect balance for your plants, ensuring they receive the right amount of light and shade for optimal growth.

What temperature range is ideal for the Austral grass tree?

The Austral grass tree, also known by its botanical name, Xanthorrhoea australis, thrives in environments with temperatures ranging from 68 to 100°F (20 to 38°C). This range is ideal for the plant, and maintaining temperatures within it helps ensure the plant's health and growth. It is vital to adapt care practices seasonally, as the Austral grass tree is very heat-loving and can be negatively affected by cold temperatures. During autumn, if the tree is grown outdoors, it is recommended to bring it indoors and place it near a bright window, keeping it away from heaters to avoid damage. Ensuring the temperature stays above 20°C during winter is crucial for the Austral grass tree's well-being, as temperatures nearing 0°C can be harmful.

What should I do if I give my Austral grass tree too much or too little water?

Outdoor plants, especially newly planted ones or seedlings, are often prone to not getting enough water. It's important to remember to water them consistently for a few months when they are small or newly planted. Once the roots are established, Austral grass trees can usually rely on rain for most of their water needs. In the case of Austral grass trees planted in pots, overwatering is more likely to happen. If you accidentally overwater your Austral grass tree, there are steps you can take to fix the situation. First, stop watering the plant immediately to minimize the impact of overwatering. Then, remove the tree from its pot and check the roots for any signs of root rot. If there is no root rot, you can return the plant to its pot. However, if there is root rot, trim away the affected roots and consider applying a fungicide to prevent further damage. Finally, make sure to repot the Austral grass tree in well-draining soil. On the other hand, if you underwater your Austral grass tree, the fix is simple. The leaves will droop, dry out, and eventually fall off. Once you water the plant more frequently, the leaves will quickly regain their fullness. It's important to correct your watering frequency as soon as you notice signs of underwatering.

When should I fertilize my Austral grass tree for the best results?

The Austral grass tree will thrive with occasional feedings, so there's no need to establish a strict feeding schedule when planting this plant. One simple way to fertilize your Austral grass tree is to apply fertilizer while watering it occasionally. Additionally, during the growing season, the Austral grass tree requires a sufficient amount of water. You can feed this plant every two to three weeks, consistently throughout its period of producing new growth.

How does the Austral grass tree react to different light conditions?

The Austral grass tree thrives under abundant daylight, leading to healthier growth. Yet, too much sun can cause light-induced damage, and too little sunlight may hinder its development. When natural sunlight is insufficient, especially in winter or shady spaces, artificial lighting can provide the necessary support for growth. This includes choosing the right type of artificial light such as LED, determining the proper distance and duration for the artificial lighting to mimic natural sunlight conditions effectively.

How do you care for an Austral grass tree in low temperatures?

In low temperatures, the Austral grass tree requires special care due to its preference for warm climates. When the temperature drops below 20°C, especially during winter, keeping the plant above 0°C is crucial to prevent damage. Exposure to temperatures below -5°C may cause the leaves to lighten in color, and after frost damage, the leaves can turn brown or black, exhibiting symptoms like wilting and drooping. To care for the Austral grass tree in such conditions, trim off the frost-damaged parts and move the plant indoors to a warm environment for cold protection. Placing the plant near a south-facing window can ensure it receives enough sunlight while avoiding proximity to heaters or air conditioning vents, which can lead to excessively dry air.

How often should I water my Austral grass tree?

Most plants can grow naturally with rainfall, but if your area lacks rainfall, you should water your plants every 2 weeks in the spring and fall, and more frequently in the summer. In the winter, when plants need less water, water sparingly or not at all. However, if your Austral grass tree is young or newly planted, you should water it more frequently to help it establish and grow. For potted plants, you can either set a predetermined watering schedule or water based on soil moisture. If you choose the predetermined schedule, water once every week or every other week, but keep in mind that it may not be suitable for your plant's specific needs. Alternatively, wait until the top two to four inches of soil have dried out before watering again. This is especially important during the summer when the plant's water needs are highest.

When is the best time to not fertilize my Austral grass tree?

For most of the year, you can regularly fertilize your Austral grass tree. This is best done during the active growing season in spring, summer, and early fall. However, it's important to avoid fertilizing during the winter. This is because the Austral grass tree enters a dormant phase during winter, during which it either doesn't grow or grows very little. Since the plant is using less energy during this time, there is no need for fertilizer.

What symptoms indicate insufficient light for the Austral grass tree when grown indoors?

When the Austral grass tree is exposed to insufficient light, especially indoors during winter, it may exhibit symptoms like smaller new leaves, leggy or sparse growth, faster leaf drop, slowed or ceased new growth, lighter-colored new leaves, chlorosis, sunscald, leaf curling, wilting, and leaf scorching. These symptoms point toward a critical need for better lighting conditions to prevent further damage and ensure the plant's health.

What should be done if the Austral grass tree experiences high temperatures?

During summer, when temperatures can soar, it is important to keep the Austral grass tree below 38°C to prevent heat stress. When the temperature exceeds 43°C, the plant's leaves may lighten, indicating a susceptibility to sunburn. To protect and care for the Austral grass tree under these conditions, you should trim away any sunburned or dried-up parts of the plant. Moving the plant to a location that offers shade during the midday and afternoon sun can also be beneficial. It's advisable to water the plant in the morning and evening to maintain soil moisture and help the plant cope with the heat.

PLATES
Xanthorrhoea australis leaf
PLATE 01 · leaf
Xanthorrhoea australis leaf
PLATE 02 · leaf
Xanthorrhoea australis flower
PLATE 03 · flower
Xanthorrhoea australis flower
PLATE 04 · flower
Xanthorrhoea australis fruit
PLATE 05 · fruit
Xanthorrhoea australis fruit
PLATE 06 · fruit
ALSO IN THE LIBRARY

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