I have two trees on my property that have just been planted, so they
are only a metre tall at the moment. They are called, Brachychiton
Discolour. Apparently, they grow to 30 meters high in 10 to 20 years.
Is there anyway i can inhibit the growth so they do not grow so high?
Or is there a there a tree that is very similiar in looks that does
not grow so high?

Hi

I'm not sure 30 metres is a realistic figure. Although it can be found
quoted on the intermet, other sources only list 10m or a little more.
There is a mention on the NSW Heritage Office site of 2 specimens 15 &
18m in a heritage garden. The NSW Dept of Primary Industries Forests
site lists the height as 16m. Hong Kong lists a heritage example 14m.

It may well be manageable,

"Considering the many variants in growing conditions there are - every
garden is different from the next - the plant size on the label can
only be very approximate. Rainforest plants grown in full sun will
always be smaller and bushier than the same species grown in the
shade. Most sclerophyl plants need sun to thrive.
The soil condition and availability of moisture will also have a great
effect on the performance of the native plant.
Some rainforest plants introduced from North Queensland have never
been grown in southern gardens before. We can safely assume that the
height they grow to as a garden subject is about one third of that in
their native rainforest habitat. It also depends on the competition
for light they have."

"Rainforest plants have the general reputation of being giant trees.
In the forest they attain some great heights mainly because they are
drawn up to the light. But in the garden their size can be reduced to
half or one third. That applies particularly to plants grown in the
open where the ample light will naturally reduce the size and enhance
their shape.
We have found that cutting grown plants from selected varieties will
remain much smaller and the height may be controlled easily by
pruning."

from http://www.fairhill.com.au/2Planting_guide2000.pdf


a similar but smaller alternative might be Brachychiton bidwillii
http://farrer.riv.csu.edu.au/ASGAP/b-bidw.html

credentials: I was an ornamental horticulture and landscape design
student and worker in the nineties but became disabled and had to
reluctantly change my career choice. my specialty and favorite part of
my job was ornamental pruning.

In the matter of the plantings:
It is hard to predict how large a specific tree might grow without
knowing the variables of the environment. Any number of things could
effect the growth of a tree; soil type and condition, pests, sun,
shade, the presence of other plants and trees, grass surrounding the
base, whether it is an arid or moist situation, temperatures, wind,
etc.. That being said these trees could grow to the height suggested
or even more if the environment is optimal for it to do so; or the
trees could be smaller and not reach more than 15 metres in that time
period.
Also the trees may grow slowly for a number of years and have greater
growth in others making it hard to maintain a certain height.

I do know one thing regarding your situation. Pruning should not be
used to control the height of a tree if it can be avoided. Pruning is
often used to do this but in an ideal world the height of a tree
should not be controlled by pruning. The reality is that people often
find reasons to do such pruning because of a number of reasons. Most
often in an ornamental situation it is becuase the tree was the wrong
choice for the situation.

So, ideally, if there are valid concerns about the height of these
trees then yes they should be transplanted and another tree chosen for
this area. That is ideal.

One other solution is to keep trees in containers to control their
size. However in certain situations this can backfire and cause more
problems than it is worth. If the roots are vigorous for example they
can outgrow the container and if the container is a permanent part of
the landscape cause it to be destroyed. This can be seen in street
trees that push up and through concrete sidewalks. Also, container
bound trees aften require more pruning depending on the species to
control its growth and this might include root pruning.

Now I am assuming you are in warmer clime but as you know the
availablity of certain species and their varieties of plants are
limited. Without knowing where you are located exactly limits my
ability to suggest an alternative. The region where I am located is
the Pacific Northwest in the United States so my knowledge of tropical
and sub-tropical plants is limited.

One suggestion is the brachychiton bidwillii or 'little kurrajong'
which is a smaller form of the plant you have already planted.

Another suggestion might be Eucalyptus  leucoxylon ssp megalocarpa,
otherwise known as the red flowering gum which has pink to red
flowers, dark green leaves and large fruit much like your current
tree. This makes a great specimen tree and its predicted growth is
5-10 meters and grows fairly quickly.

I hope this helps.

Salvatore