have 5 evergreen Alder trees (Alnus jorullensis) approx.
3 years old and 3 m high x 2.5 m wide. I am unsure as to whether
I should leave the trees to grow in their natural form, or if I
should remove the lower limbs for a nice clean trunk. If I chose
the latter, will this ruin the look of the tree, as I have not seen
mature trees anywhere as yet and do not know how they will eventually
passed your question on to Jim Antill, one of our landscaping experts.
Most trees that have
a definite top leader (exhibit "apical dominance", in trade jargon)
can have their lower canopy removed progressively to create headroom,
etc. We call it "siding-up". The rules are:
- Work out WHY you
want to cut the tree what exactly you want to achieve.
- Make "proper" cuts,
i.e. DO NOT EVER cut the branch flush to the stem, thus damaging
the branch collar (that slight swelling that often occurs at the
base of a branch). If you do, you wreck the tree's natural defences
against infection, that are present in the collar, and lay the
tree open to the incursion of rotting fungi.
- Never remove more
than a third of the canopy in any one year period, preferably
only 20%. This reduces the shock to the tree and allows it to
retain its disease resistance. (Alders are pretty tough, however.)
I'm not familiar with
A. jorullensis either, but it's fair to say that the more
you side-up a tree, the more it will build canopy further up and
thus get taller. If this is what you want and if the site is reasonably
sheltered, fine. If not, go a bit easy!
Note: Alnus jorullensis
is also known as A. acuminata.
by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor
of Resource Management.
with permission from NZOOM Home and Garden content,
from the previous
The views expressed here are not necessarily those of the RNZIH