A Queensland bottle tree (which should not be confused with a bottlebrush shrub) does not need trimmed at all if it is in a situation where it has plenty of growing room. Ideally, the bottle tree (Brachychiton Rupestris) should be situated in an area where it gets plenty of sun, the soil is well drained and it receives moderate protection from prevailing winds and winter chill. Bottle trees are hardy in US growing zones 9-11. As the name implies, Brachychiton Rupestris is native to Australia and grows well in most areas.
When to Trim a Bottle Tree
Bottle trees respond well to trimming, even though it is not essential for the plant’s health. It will make the top fuller and bushier. The primary reason to trim a bottle tree is to restrict its growth to an area or to keep it suited to growing in a pot or as a bonsai. The swollen trunk and narrow top make an excellent conversation piece when grown as a houseplant. Even though the tree can grow to as tall as 40 feet with a canopy that might spread thirty feet wide, pruning can keep a potted tree or a tree in a restricted area from overgrowing available space.
No Need to Trim for Pests
While there are some pests that can affect bottle trees, trimming is not usually the solution. Phymatotrichopsis Omnivora, a type of root rot is the primary enemy of bottle trees. There is not, at the time of this writing, a known solution for this difficulty save to select disease resistant varieties of bottle tree and to plant the tree in a location that is well drained with soil suited to bottle tree growth. Spider mites are another pest. As with other sorts of plants, spider mites infect the upper part of the plant. Since these insect are resistant to sprays, the best solution is a predator insect. Seed weevils sometimes infect the seed pods of bottle trees. This does not affect the health of the tree, but can make it difficult to get seed for fresh plantings. The best solution is to remove the affected pods from the tree, rake the ground beneath it, and wait for next year.
Trimming Your Bottle Tree
Before trimming your bottle tree, clean your equipment and make sure that your pruners are sharp. Clean shears, pruning saws and pruning knives help prevent carrying disease from one plant to another. Sharp implements make neat cuts that are easy to seal, keeping out damp that can cause rot. Think of trimming your tree as doing surgery on it, and you will not be far wrong. Clean sharp implements do a better job.
Shaping Your Bottle Tree
The interesting thing about bottle trees is their wine-bottle shaped trunks. When you trim or shape the tree, you want to reveal the bottle shape without destroying the tree’s ability to photosynthesize. The general rule for trimming any tree is to cut away no more than 1/3 of the tree’s overall canopy. That way, the tree will be able to take nourishment from the sun and continue to grow. Yet, at the same time, you can restrict its height and width so as not to over-grow other plants in your garden or neighborhood. When the tips are cut off the branches, the tree tends to put out two or more added shoots at that point, which encourages it to have a fuller appearance.
Bottle Trees as Indoor Potted Trees
One way to restrict the growth of potted bottle trees is to keep them in a relatively small pot. Eventually, however, this will mean that not only will the top of the tree need trimmed, but that excess root growth will also need to be cut away unless you wish to simply move the tree to a larger pot. Giving it a larger pot, however, will encourage it to grow larger.
To trim the roots of a bottle tree that is becoming too big for its pot, and perhaps to be more easily handled inside your house, first gently remove the tree from the pot it is in. Using a sharp knife, trim away about ¼ of the outer roots. You can then return the tree to its original a pot with fresh potting soil. Adhere to your normal watering regimen, and keep a close eye on your tree for a week or two to make sure that it does not go into shock.
Bottle Trees as Bonsai
Seedling bottle trees can be trained into adorable bonsai. Their hardy, adaptable nature and their ability to be readily grown from seed, make them an excellent subject, while their unique trunk shape is attractive in any setting. As with most bonsai projects, the shape of the container, feeding and watering is as important as trimming and wiring.