There are three schools of thought on pruning a glauca grass tree. The first is that they do not need to be pruned. The second is that all dead, brown growth should be trimmed away to encourage next season’s healthy growth. And the third is that glauca grass trees naturally grow in areas that tend to have seasonal grass fires, and that they are healthier after being subjected to a grass fire.
Who is right? That is a very good question. Let’s take a look at each school of thought and consider the various aspects of it.
No Pruning Needed
Glauca grass trees are native to Australia. Clearly, they grow in the wild without any assistance from anyone. Leaving a healthy grass tree alone to grow as it will is probably a perfectly viable choice. There are, however, some caveats that could indicate that pruning is both necessary and desirable. These include fire prevention, esthetics and perhaps the health of the plant itself.
Pruning by Hand
To prune a glauca grass tree by hand, use a piece of string and tie up all the healthy plant fronds. This will keep them out of your way, and help prevent your being poked by the sharp points. When handling plants that have stiff leaves, it is a good idea to wear gloves, eye and ear protection. While the ear protection might surprise some gardeners, ER doctors are reporting gardening ear injuries. The long, narrow leaves are sufficiently slender to enter the ear canal and some species are sufficiently sharp to pierce the eardrum. A sports helmet that covers the ears or even a sturdy pair of headphones will do as ear protection.
With the upper fronds securely tied up with string, remove all yellow or brown fronds from the trunk. Use a sharp pruning tool such as long-handled loppers or a sturdy pruning saw. When all the brown or yellow fronds are removed, gently release the healthy green fronds.
Bundle the cut fronds into industrial strength trash bags and dispose of according to local ordinance.
Pruning by Fire (Not Necessarily Recommended)
While this is a traditional method of pruning a grass tree, not all types of grass trees respond well to it. Although fire seems to stimulate blooming, it is not necessary. Before using this pruning method, check with a lawn and garden nursery that specializes in Australian native plants. Be sure of the type of glauca grass tree you are growing.
For example, the grey glauca grass tree, X. glauca angustifolia, is very sensitive to burning. In fact, it can be killed by a forest fire and needs protection in areas that are prone to fire.
A grass tree that has been hand trimmed should not be burned. The dense, “grass” skirt is what protects the stem during a forest fire.
So why do some people favor this pruning method? It has to do with esthetics and ease. One name for these trees is Balga Grass Plant. European settlers in Australia thought that the Xanthorrhoea Johnsonii plants, with their blackened trunks and fresh bloom stalks, looked like a native Australian getting ready to hurl a spear.
What Does Burning Do
Many people favor burning and you can see an example on Youtube of a man using this method. During a fire, the resinous sap from the grass tree melts and oozes out. When the trunk cools, it forms an almost glasslike black surface on the trunk, giving the tree its nickname, Balga.
The method has the advantage of being quick and it can stimulate certain types of grass tree to bloom. But it can kill certain other types of grass tree, so be very sure that you know which kind of grass tree you have in your garden.
Back to the Beginning
As noted above, it is not necessary to trim the brown or yellow growth from the tree in order to maintain its health. With that said, an excessive amount of brown or yellow growth could indicate that the tree is in poor health.
While grass trees are not prone to insect pests, there are a few that can infest the trees. Scale and mealy bugs both favor grass trees. However, root rot caused by over watering or poor drainage is a more likely culprit.
Blooming Requires Patience
It would be a mistake to assume that burning the dead growth on your tree will stimulate blooming or restore a sickly tree to health. Although the trees have developed a way of coping with fires, burning is not needed for health or blooming. Indeed, what it often needed is to feed the specialized bacteria that grow around the roots of the tree and a great deal of patience. Grass trees grow very slowly. It can sometimes take as long as twenty years for one to mature enough to bloom. When it does bloom, a single bloom stalk will produce hundreds of seeds.
Pay close attention to the way your tree is growing, and trust the tree to know what it needs.