Evening star., 1946-06-30


checked by high soil temperatures,
lack Of sufficient moisture and by
insufficient air circulation in the
soil. The first two are common
summer problems Of Washington
gardeners, whether they grow vege-
tables or flowers.
Summer temperatures above 80 or
95 degrees tend to raise soil temper
atures to point where plant growth
Is retarded, If not stopped. This Is
especially true of those plants which
are commonly thought of as "cool
weather" crops, such as cabbage,
broccoli, lettuce, primroses, roses,
etc. They need a cool moist root
run. Both high soil temperatures
and lack of moisture adversely affect
their growth.
If there is any question in the
gardeners mind how these condi-
tions apply, he need only to mulch a
part Of a bed or row Of plants to
observe. 1t is difficult to separate
the effects of soil temperatures and
of moisture, since they are definitely
inter-related. Dry soils heat quickly
Moisture evaporating from the soil
tends to lower the temperature. A
moist soil is generally a cool soil
and SO on.
Cultivation is probably more
widely used than any other correc-
tive method. Cultivation retards the
loss of moisture as we'll as helping
moisture penetrate more quickly. A
well-pulverized dust mulch retards
evaporation, permits air to reach the
plant roots and keeps down weed
growth.
Paper Mulches Easy to Use.
Paper mulches have been widely
written about since the large pine
apple plantations in the Hawaiian
Islands adopted them. They are
useful and easily applied, although
it Is doubtful If they will do more
than retard a rise in soil tempera-
ture. They do check evaporation
and control weed growth. Paper
mulching strips are not costly, bu,
the care necessary in laying ano
using seems to discourage thei,
adoption by local gardeners.
Mulches of plant material, such as
compost, peat moss, leafmold
weeds, ETC., are all useful, although
the depth of the application has
much to do with their effectiveness
A layer an inch or two in thickness
Is certainly better insulator against
the suns rays than one only u or !:
inch thick.
Grass clippings soon dry out ane
what seems at first to be a gooc
layer soon becomes a very thin ant
usually ineffective one. If put OF
thick, there is danger of heating
They are best applied after curing
fer a few days in full sun. Weed
seldom mat down and heat as easil,
as grass clippings. Chopped corn
stalks. while useful, become avail
able too late in the season to be 0
much assistance. Sawdust is an ex
cellent insulator, but must have al
application Of nitrogen to protec
the growing crops. The bacteri
that attack and break down the saw
dust need nitrogen and will rob tn
soil unless 1t is supplied in the forr
Of fertilizer.
/ Compost Works Best.
4 Under most conditions the mos
effective and desirable mulch
compoSt-rotted vegetable matte
Few gardeners have enough t
mulch more than a fraction of thei
garden. The compost can be spade
into the soil after it has served a
. mulch. Weeds, cornstalks an
other material may be plowed O
spaded under, but are not so easil
mixed. Sawdust may be spaded unde
If there is an abundant supply o
nitrogen in the soil. It is safer
turned under in the fall when ther
Is less likely to be a detrimental eff
feet on plant growth
Stable manure, ordinarily too ex
pensive for large scale use, is an ex
cellent mulching material, although
its appearance and odors make j
undesirable near the home.
/ Mulches of compost if properly ap