Wednesday, December 5, 2007

Fast growing trees for shade.

There are certain times of the year when we suddenly wish we had a large shade tree to sit under in the garden. It's at that point when you want a fast-growing tree. There are a few points to remember though when you enter a garden centre - trees that grow fast will often only live a relatively short amount of time, they need space to grow and there is no such thing as a tree that is only a metre wide all the way up and conveniently stops at 4 metres. Unless you want conifers but they are neither shady nor fast.
If you want a deciduous tree for the north side of your house (southern hemisphere) for summer shade and winter sun you will need to be prepared for "mess". In nature that "mess" rots back into the ground. In modern life it has become a hassle that people don't want to deal with. The best thing to do is to expect the leaf fall and use it for compost or leave it as mulch where it falls. It will feed the tree and the soil.
Deciduous vines are also great for the north side. Grapes on a trellis are excellent, with bunches hanging down being easy to pick when ripe.
Keeping the western side of the building cool makes a huge difference to the evening temperatures inside a house. Sun tolerant, evergreen shrubs to 2 metres are good for that side of the building. Deciduous trees or vines are also good along that side.
I'm always a bit disturbed when I see potentially large trees placed much too close along a front wall. Trees need lots of room, even non-invasive ones, so planting a large tree near a wall is a very bad idea. At least a metre would be the minimum. I always warn people that Ficus species should be kept in pots, not the ground, unless they have a very large area of open space without pipes and power-lines.
Beware also of trees that sucker. We have two in our garden; we planted them before we really understood how bad they can be. One is the Paulownia tomentosa - powton or princess tree. It is a beautiful tree; large soft leaves, stunning lilac foxglove type flowers in spring. We keep it small by cutting it back to a stump every year. When we leave this house though, we want to dig up the main base and take it with us. However, this tree suckers form any roots that are left, so we may leave a monster of multiple proportions here. Instead of one sturdy powton, it may end up being all over the garden. Hopefully we'll get enough warning to do it properly and not leave a nightmare for the next tenants.
The other, also an extremely good-looking deciduous tree, is the Gleditsia tricanthos var. inermis - Sunburst. It can sucker, making very nasty spines on fast growing shoots from the parent trees roots. We have not disturbed the soil anywhere around the base, so it is behaving here, but in Queensland they have become bad bad weeds, as they are hard to approach to kill them, sending up more suckers when the first lot are killed.
Take some time to consider what tree you like. If you see one and you don;t know what it is, pinch some leaves or take a photo and take them to a garden centre. They should be able to tell you what it is.
Trees are a much needed part of the landscape. There are lots of choices in size, habit, flowers, fruits...plant a tree soon. It's good for you.


Garden Wise Guy said...

Great advice regarding the "double-edged sword" of fast growing trees. I call them "James Dean" plants - live fast, die young.

Very nice blog you have going. Of course, being in the northern hemisphere, I have to read it upside down and remember that your hot north-facing exposure is my south-facing side.

Keep up the good work.

Fast Growing Trees said...

From among the popular shade trees, the paulownia and the gingko tree are ones you can expect to last till a very long time. The Gingko tree especially is widely recognized as a ‘living fossil’.
Some are known to have existed for 270 million years!

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