Author - Mark Higgins
Deciduous trees hold a lot of fascination for people as bonsai but unfortunately here in Perth we don’t have too many examples growing locally that we are able to copy.
There are two main reasons we like deciduous trees and they are the color of the Autumn foliage and the skeletal silhouette during winter.
Some of the southern and hills areas are lucky enough to receive the right temperatures to consistently develop the red, orange and yellow autumn tonings. However in the metro coastal areas, more often than not, the color is weak and is flawed because the foliage has been damaged by the wind.
Quite often deciduous trees don’t completely defoliate which is the case with some Chinese elms and liquid ambers (especially the formosana). There is one liquid amber growing near my house that until recently still had its foliage from last season which is a first as far as I can remember and this partial or non defoliation just goes to show how much variations in climate from year to year can affect our tree’s growing habits.
I haven’t been growing deciduous trees for that long, although I have had a couple since starting out in bonsai and over the last few years there are one or two things that I’ve worked on and the results are starting to show.
Grow your trees from cuttings. I really can’t tell you the last time I purchased a stock plant. If you grow your own stock you can be very selective and discard the rubbish from the beginning. You might only keep 2or 3 plants of each variety and if you have several varieties, then you will have plenty of trees to work with.
Plant the cuttings in plastic pots for a season and then the following year pick out the ones that may have an interesting line and plenty of roots growing around the base. You now need to get these into the ground for a couple of years to thicken up the trunk and develop the Nebari. When planting them, don’t be afraid to position the roots so that they will look as good as possible.
I usually let them grow for two years unchecked and then going into the third year lift them from the soil and sort out the Nebari. After this put them back in the ground and don’t worry about developing the branches at this point but focus on the trunk line.
The next year you might need to cut the tree right back and start to develop the taper of the trunk line. Depending on how thick you want the trunk will depend on how long you leave it in the ground.
To develop the branch structure I have been removing the tree from the ground and working on it in an oversizee training pot.
The one technique that has made growing these trees easier is using the plastic colanders, they are an absolute God send - thank’s Peter Odin for your secret. When grown in colanders the trees are easy to remove from the ground by simply digging around the pot and you also end up with a much better and finer network of roots.
The silhouette of branches is something that is developed over consecutive seasons. Remember the old two by two technique, it is just a matter of patience and time but if you only grow two new shoots each year then in four years each branch will have developed into 8 sub branches.
Some trees such as Chinese elms have a naturally short inter nodal space but in a lot cases the distance between each leaf can be quite substantial and generally gets larger as the branch grows. Pruning back to the first two or 3 buds and also leaf pruning in the early stages does help to reduce this distance and helps to create a more compact structure.
If the basic framework of the tree has been developed, pinching out the tips of new growth will help keep the tree compact and create a fine network of branches with short inter nodal spacing.
Prune back excessive branch growth during late winter, if you prune back just after the leaves have dropped (and never do it before this) then you risk the branch dying back as sap is withdrawn from the branch and trunk. If it is a thin branch I will cut back to about 1cm in front of the last bud I wish to keep to avoid losing the bud from sap withdrawal.
Most deciduous trees will grow very strong at the apex so you will need to keep this area under control by pruning out excessive and strong growth. Leaf pruning only at the Apex will also slow down the growth rate in this area.
Most deciduous trees have a very thin cuticle or wax covering on the leaves and are prone to excessive transpiration, it is generally the wind that causes the most foliage damage, not direct sunlight. Use a slightly deeper pot than you normally would and a try little bit of extra coco peat in your soil which will help keep the moisture levels up. A humid environment will also help keep the foliage in its best condition.
These are just some of the basic things to consider.
The key to having a good tree is selecting the right material in the beginning, if you don’t like foliage with crisp edges then don’t use a maple, try a liquidambar, they don’t develop the same fine network of branches but are a little hardier and can still produce good color.
Crepe Myrtles are good offering flowers, autumn color and a wonderful bark texture / color. They can also develop a fine network of branches but the trunk growth is very slow, especially in a pot.
Chinese elms might not develop color every year or drop all their leaves, depending on where you live, but they will grow well, are tough, hardy and are one of the fastest developing trees as a bonsai. Use branch cuttings to start with but they will also grow well from root cuttings.
If a deciduous tree near you hasn’t started to bud yet then now is a good time to take a few cuttings or even consider an air layer. So what are you waiting for, get out the secateurs and start pruning up some cuttings.