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caring for your grass trees                  xanthorrhoea johnsonii

Xanthorrhoea johnsonii is one of 28 species of grass trees in Australia, best suited to the ACT and NSW climate. They have a trunk that is typically black as a result of bush fires, that adds to their visual impact; hence the name “black boy”.

Your purchase of these stunning trees from Provincial will enhance your outdoor space and give you years of pleasure. An impressive feature, your grass tree will add value to your home and lifestyle experience.

Grass trees are extremely hardy if well cared for in the initial stages of transplanting from the wild.  Only a small number of reputable companies successfully transplant grass trees and our supplier is one of them.

Be wary, as it can be difficult to see whether a tree has been correctly transplanted for many months as its reserves are slowly depleted. Our trees are not sold for around 12 months after transplantation, or until they display strong root and new top growth. 

growth rate and dormancy

Grass trees are extremely slow growing. Did you know that in poor bush soil the trunk will grow approx 9mm per year? They take up to 10 years to start forming a trunk, and a tree with a 1 metre long trunk could be 100 years old! In better soils, growth is slightly faster and trees are more likely to grow multiple heads.

Grass trees may spend the first few years after planting settling in and deciding whether they like the spot they have been planted.

It is normal for grass trees to remain dormant after flowering with no new leaves appearing for months at a time - some of the leaves may also appear brown.

Grass trees will always grow more vigorously in the garden than in pots as they can access the right balance of nutrients themselves.

minimise root system disturbance

When moving a grass tree from its pot, be extremely careful not to crack or disturb the roots. Grass trees do not have a strong network of roots to bind the soil around the plant.  Active roots are black and fleshy, and can be easily damaged. 

When planting into the ground you can leave the plant in its pot and cut the base from the pot, keeping its walls intact.  Place the plant in the hole burying it no deeper than the existing soil level, then cut the rim off the top of the pot.

Browning or yellowing of new leaves or general lack of vigour means your tree could be unhappy, and may indicate shock. 

planting and drainage

Well draining soil is essential to a healthy grass tree. If you have poor drainage in your soil, try a liquid ground or clay breaker to change the soil structure.   Liquid ground breakers require ongoing application as they leach from the soil quickly.   

If planting in the ground, build the area up with sandy soil mixed with a medium anything that will provide bulk without nutrient such as gravel (not bluestone,) rocks, broken bricks, coarse sand or pebbles. The garden bed should be built up at around 1metre high, with very good drainage below.  Two handfuls of chicken manure pellets over the soil can also aid in a smooth planting process.

Do not plant in or on top of clay, boggy soil or in areas where water can pool and sit for some time.

If creating a decorative potted feature with your grass tree, choose a pot that is larger than the one it was purchased in.  Place large rocks, pebbles, gravel or broken bricks into the bottom of the new pot to maintain good drainage between the two pots.  Place the decorative pot on pot feet or similar for additional drainage.  Mulch well after planting.

If desired, cut the rim of the purchased pot away.  Place the grass tree into the decorative pot and complete with a large pebble mulch to add aesthetic appeal.

Grass trees prefer full sun but will also tolerate part shade.

watering

Upon planting, water the grass tree in well to eliminate air pockets.

If drainage in the soil is good, and there is no rainfall, water your grass tree about once a week in Summer and once every 10 days approximately in Spring and Autumn.

If planted in Spring or Summer, water about twice a week for the first month, then gradually reduce watering so the plant will acclimatise to the amount of water.  It is best to give the plant a thorough soak when watering, and depending on the size of the tree, expect to use between 3 – 4   9 litre buckets of water.

If your tree is in a pot with correct drainage it will be difficult to over water it. Water weekly, enough to soak down to the roots or until the soil dries out to 10cm below ground level.

setting fire to the crown

Flowering in nature occurs after a bushfire, and in the absence of fires, Xanthorrhoea will only flower in a good season, or if they are very healthy plants.

Setting fire to the crown is not recommended and if undertaken should not be done more than every 6 – 8 years. 

Placing a cardboard box filled with newspaper over the crown and setting fire to that is an easier method.  The foliage will burn and new foliage will develop after around 6 months. Do not use this technique if your grass tree is diseased or stressed, as this will cause further stress.

fertilising

As chemical fertilisers are not present naturally in Australian soils, it is preferred to use one of the following though be careful not to over fertilise.

  •   Seasol
  •   small amounts of cow/chicken manure
  •   fish emulsion
  •   sulphate of potash

If your plant looks unhealthy, ask your local garden centre for advice.

health problems

The most common problems are with drainage, transplant shock or nutrient toxicity (from excess application of chemical fertilisers).

If it looks unhealthy (browning, yellowing or showing lack of vigour), ensure the drainage is perfect, water with Seasol or fish emulsion for 2 months in the growing season or until it looks happier. If the leaves are almost totally brown, try burning as much of the grass as possible and cut back the rest until it is bald. Mulch well, water weekly until the new grass is over 30cm.

Grass trees are also susceptible to root attack by the Cinnamon Fungus (Phytophthora cinnamoni). This fungus attack can cause a gradual decline in health, eventually leading to death. Water spreads the fungus and it thrives where there is lots of moisture. Try to keep the garden free of extra moisture as there is no fungicide to combat this problem.

Although we take every effort to care for and nurture your plant and are happy to give any advice you require, Provincial cannot guarantee the life of the plant once it leaves our nursery. By following the above guidelines you are giving your grass tree the best chance for a long, healthy life.


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