The Plant Man column
for publication week of 06/19/05 - 06/25/05
(664 words)
###

The Plant Man
by Steve Jones
www.landsteward.org


Smart watering keeps mature trees lush and healthy all summer


In this column last time, I discussed the special needs of new, young
trees
during their first summer months. But let's not forget that mature
trees,
whether they are young adults or senior citizens, need your attention
too.

Maybe it goes without saying, but I'll state the obvious anyway: trees
need
water. Water helps a tree manufacture its "food" and provides the
conduit to

flow that food through its system. Additionally, water provides the
essential coolant to help a tree cope with the summer heat.

If you go to the gym and work out, you know how quickly you can lose
moisture and how important it is to replace it. Now think of a mature
tree,

weighing many thousands of pounds, sweltering under the summer sun.
Large
trees can lose a lot of water. How much?

Take, for example, an oak tree that is 90 feet tall with a 90 foot
canopy
spread. When the temperature reaches 90 degrees Fahrenheit, the tree
can
lose up to 90 gallons of water in a single day! That's according to
David
Robson, Extension Educator / Horticulture at the University of
Illinois,
writing in an online article on summer tree care.

You can read that entire article at
http://www.urbanext.uiuc.edu/greenli...gl9807.03.html and you can

click on a direct link when you go to my Web site www.landsteward.org
and
find this column under the Plant Man heading. You can also find
hundreds of

direct links to other useful garden and landscape information at my Web

site.

Although some of a mature tree's roots can be quite deep in the ground,
you
might be surprised to know that the roots that absorb most of the water
are
located only about fifteen inches or so below the surface. These are
called

feeder roots and most of them are NOT located at the base of the trunk,
but
rather at the tree's drip line.

However, the feeder roots of a large, mature tree can extend well
beyond the

dripline, and can be quite fine, even hair-like. Drought-like
conditions
can dry out these delicate feeder roots. When Nature isn't providing
the
necessary moisture in the form of rainfall, your mature trees will
welcome
your assistance.

It is far better to provide sufficient water in a single, saturating
application than to apply the same amount of water over several,
shorter
applications. Why is this? Several short waterings are likely to draw
the
feeder roots towards the surface where they can dry out and wither as
the
sun dries the soil.

Single saturation soakings encourage growth of feeder roots deeper
below the

surface where the soil temperature is also cooler.

Mr. Robson's article reminded me of an old landscaper's trick. If
you're
using a sprinkler, place an empty tuna can (approximately one inch
deep) at
the tree's drip line. Check the can from time to time as the sprinkler
does

its work. When the can is full, empty it and allow it to fill up one
more
time.

In my previous column (archived at my Web site, in case you missed it)
I
specifically addressed the watering needs of new, young trees. But how
much
water should you expect to apply to more established trees? Here's a
handy
rule-of-thumb, with trunk diameters (calipers) shown in parentheses:

Small to medium trees (1" - 9"): 10 gallons/inch
Large trees (10" and up): 15 gallons/inch

If you are unsure of your tree's diameter, simply place a ruler against
the
trunk and eyeball it.

Keep an eye on the rainfall this summer, either using a rain gage or
getting

information from local news sources. Supplement Nature's shortfalls
with a
watering program and you'll be enjoying lush, green trees for many more

summers.

The Plant Man is here to help. Send your questions about trees, shrubs
and
landscaping to and for resources and additional
information, or to subscribe to Steve's free e-mailed newsletter, visit

www.landsteward.org