Fertilizer is always an area of many questions. The place to start
is a soil test. This will tell you where you are starting from.
Basic soil test levels for phosphorus, potassium and soil pH should
be in the neighborhood of 40, 350 and 6.1, respectively. These
numbers will provide a great environment for grass. Phosphorus and
potassium are on a pound-per-acre basis. This must be considered if
you use labs that report in parts per million, which will give
numbers half as large. Grass will really grow in very poor
conditions, but it certainly won't have that manicured lawn look
many strive for.
Lacking a soil test, or being at recommended
fertility levels, general maintenance applications provide a pound
each of nitrogen, phosphorus and potassium per 1,000 square feet of
lawn area in May and again in September. Really lush lawns will
usually have twice as much nitrogen applied in a season, but split
among four applications.
If you decide to try late seeding this spring, remember a couple
of things related to weed killers. First, you can't use crabgrass preventer in the spring if you put down seed. The crabgrass
preventer doesn't know the difference between grass seed and weed
seeds. The second rule is to mow the new seeding at least three
times before trying any broadleaf weed killer. Generally this means
spring broadleaf control doesn't happen when you seed in the spring.
The end result is if you seed in the spring, you control weeds in
the fall. Seed in the fall, and you control weeds and crabgrass in
If you do plan to use a crabgrass preventer, time it so it is on
about when the forsythia blooms. That is assuming it actually blooms
this year. Many of the flower buds were cold-damaged in the winter
we just went through. This would be the approximate soil and air
temperature needed for the crabgrass to germinate. About now is a
good guess, but the date can vary widely with the weather. Many
crabgrass preventers also only last for four to eight weeks, so plan
on repeating the application in June anyway.
If you have missed some early germinating crabgrass, you can try
one of the post-emergence chemicals —
put on the actual crabgrass when it is small —
such as DSMA or MSMA. They may temporarily discolor lawns, and all
the statements about new seedings apply to these as well.
One last item for the week. Many lawns have brown spots or
patches. In most cases these are a warm-season perennial grass such
as nimblewill. There is no selective control for these grasses,
meaning glyphosate (Roundup). These spots green up slowly and brown
out early. The best plan is to spray them in late July when they are
growing, then put down new seed in mid-August.
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Early spring lawn weed control
Each year, the winter annual weeds chickweed and henbit run No. 1
and 2 in the early spring as lawn and garden weeds. Winter annual
weeds can actually germinate in the fall, carry through the winter,
then get going very early in the spring. They also are done by the
heat of the summer, leaving seed to germinate again later in the
Right now chickweed stands out in yards because it is quite
abundant and has a lighter green color than grass and most other
weeds. It is even evident as grass is just beginning to green up.
There are two types: common chickweed and mouse-ear chickweed.
Henbit is easier to identify since it has purple flowers and smells
like mint. It is very noticeable right now.
The straight 2,4-D that is used on dandelions seems to act like a
fertilizer for chickweed and other problem weeds. The 2-4D is a
growth regulator, and if it doesn't actually kill a weed, it does
make it grow faster. Combinations that contain 2,4-D, MCPP and
dicamba are rated very effective on chickweed, henbit, red sorrel,
purslane, white clover and others. These combinations are sold under
several different trade names. You can find these at most hardware,
discount, and lawn and garden stores. Just check the label under
active ingredients and check for two long chemical names and dicamba.
You can also check to see that it says it will control chickweed and
This group of chemicals is effective in the 50-degree range and
up. It just takes a lot longer for control with very cool
temperatures. Remember that the control time for most broadleaf
weeds is early May. As with any chemical control, read and follow
label instructions very carefully. On these product labels there
will be some cautions that you should be aware of concerning injury
to sensitive plants. This is because dicamba can drift as a vapor
for a few weeks after you apply it if the weather gets hot and
University of Illinois
Extension director for Logan, Menard and Sangamon counties]