Evening star., 1949-01-02

/ 1CdG Huns.
| Shredded redwood bark.
in decaying give off tannic acid.
which helps to keep the soil prop
erly acid, a condition necessary to
azaleas and rhododendrons.
The decaying leaves are most inn
portant to the health and vigor Of
such shrubs during the summer,
too, as it keeps their shallow
growing. roots cool and moist. In
other words, do not remove the de-
caying leaves the first warm day in
the spring when the urge to rake
and burn Is rampant.
Requirements for q Good Mulch.
But let us get back to our pri-
mary concern at this season-ap-
plying mulch to keep the ground
frozen. First in Importance. it
should not be applied until after
the ground is frozen lest the normal
ripening processes taking place
within the plant be interrupted be-
fore they are complete.
What does it take to do the job
of keeping the ground frozen and
the plants healthy?
/. The material should have
enough substance to last through
out the winter without blowing
away.
2. 1t should be porous enough to
admit air so as to avoid smothering
or rotting the plants.
3. It should not contain injurious
chemicals or weed seeds.
4. 1t should be effective in MAIN
tanning a reasonably constant soil
temperature even during periods Of
prolonged mild weather which we
normally expect in February or
March as well as during the occa-
sional cold spell" when the ther-
mometer may sag (as it did last
week. to 1915 degrees above zero.
This is, however. a combination Of
two things-kind of material and
its depth.
S. The mulch should be reason
ably available, easy to apply and
not unduly expensive.
OF the six or eight commonly
mentioned mulching materials, glass
wool is, according to tests made by
Cornell University, the best mate
rial. A layer 2 inches thick not
only admitted enough light so that
plants retained their leaves through
the winter, but the air circulation
was excellent and there was no ac-
emulation of moisture. There was
a minimum fluctuation of soil tenn
perature as compared with the
common materials.
A 6-inch layer of oat straw gave
slightly more desirable results than
other types of straw. 1t did not
pack so tightly and thus permitted
air circulation and not too great
an accumulation of moisture. Oat
straw normally contains weed seeds.
Temperature fluctuations were
greatly reduced.
Salt hay, which is not easily OBJ
tanned in this area. was superior to
the straw in that it did not contain
weed seeds and was less likely to
absorb and hold moisture.
Excelsior was less effective than
the other mulching materials. It
tends to hold moisture and thus in
duces rot.
Oak Leaves Admit Air.
Oak leaves are a good insulating
material and temperature fluctua-
tions are, greatly reduced. Oak leaves
do not pack as readily as do most
other kinds of leaves, hence they
give better air circulation. However,
all leaves hold considerable moisture
and while the oak leaves are not
quite as bad as some, they cannot
be classed as desirable winter
mulch because of this. Even so, II
the oak leaves are scattered over
brush to keep them from packing
they will do fairly creditable job.
Fresh strawy horse manure, used
to depth of inches, was not much
better than the excelsior. 1t held
moisture so that the soil remained
wet and soggy throughout the win
ter, and was source Of weed seed.
Because of its moisture the manurs
did not greatly reduce soil tempera-
ture fluctuations.
Pine needles are sometimes used
as a mulch in this area, perhaps not
as much as they should be. They
are as effective as oak leaves in
maintaining an even soil tempera-
ture; admit ample air, but will hold
some moisture. Freshly fallen nee
dies are to be preferred over those
partially decayed. The latter tend
to pack and exclude air, and they
|disintegrate so quickly that they
may not last throughout the winter.
Evergreen boughs are excellent
for keeping the soil frozen. They do
not collect and hold moisture, and
they will admit all the air needed.
They should be applied thickly
enough to exclude sunlight from the
soil.
Peat Moss Is Good Material.
Peat moss, if blowing can be pre-
vented, Is one of the best of the
more common mulching materials.
A 3-inch layer effectively controlled
soil temperature fluctuations. A
coarse grade, commonly known as
poultry litter or agricultural"
grade, admits sufficient air, and if
applied in a layer not greater than
3 inches, does not hold too much
moisture.
Shredded redwood bark, available
occasionally, is an excellent insu-
lator and does not hold too
much moisture. A layer an inch
thick is adequate. Bluestone chips
(1a inch size). If applied an inch
thick, will give good results, but
they should be used only where they
may be left the year round. They
are most likely to be of value in the
rock garden.
The choice of mulching material
will depend largely upon availability
and relative costs. Some gardeners
will 60 into the woods and collect
leaves Cor pine needless, or pine
boughs. Others will buy whatever
material seems most economical.
Regardless of the material used,
its removal in the spring should not
be done In such a way as to cause
great injury to the plants.
Too often we feel the urge to