Weekly Express-News Article
By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist
Saturday, March 3, 2007
It is too early to fertilize your lawn, but there is still plenty
When the weather improves in February, many of us have the urge
to fertilize the grass thinking the lawn will green up faster.
It is not true. The green weeds in the lawn benefit by the nutrition,
but not the dormant or semi-dormant lawn grasses. For a grass
to utilize the nutrients in fertilizer, the grass must be actively
growing. That growth does not begin until the air and soil temperatures
have increased for a period of time, sometimes after April 15.
If you apply the fertilizer before then, much of the nutrients
are wasted if your goal is to benefit the lawn.
There really is no reason to ever use a “weed and feed”
fertilizer/herbicide in the San Antonio area. The timing is just
not correct. We apply pre-emergent herbicides now and in August,
and we fertilize in late April and in October. The timing never
coincides. “Weed and Feeds” are accidents waiting
to happen because too many folks forget that the products include
herbicides. The herbicides will kill vegetables and flowers. Use
fertilizers and herbicides, but use them separately.
Aeration and top dressing is something to do right now that
will benefit the lawn greatly. Rent a core removing aerator, aerate
the lawn, and then spread compost one-half inch deep over the
surface of the lawn. The process helps address compaction and
introduces organic material to the root system with the net effect
that you have a healthier and more water efficient lawn. SAWS’
customers will receive a rebate for $100 - $150 depending on the
size of your lot. Visit the SAWS’ website at www.saws.org
for the application and more information.
If crabgrass and sandburs or other summer weeds were a problem
in 2006, apply a pre-emergent herbicide such as XL or Amaze in
early March. The pre-emergents, when applied as per the instructions
on the label, do a good job of preventing the germination of annual
weeds. Sandburs, are especially tough to control. They require
a second application of pre-emergent herbicide. In addition to
this application in early March, add another layer in May as per
Winter weeds are the issue now. Your lawn may have dandelions,
rescue grass, winter rye, bedstraw, henbit, and thistles. Keep
the winter grasses mowed and they can be quite attractive, the
problem is that any winter weeds will stress the lawn. Pulling
them by hand is very effective if you have the time. It can be
satisfying because most of the winter weeds are easy to pull.
It is also good exercise. Toss the weeds in the compost pile.
If you would prefer to use a herbicide, consider Green Light Wipe
Out. It will kill most of the weeds listed and does not hurt St.
Augustine grass as long as you follow label instructions.
The live oak leaves are dropping on the lawn now. The most environmentally
appropriate, and also the easiest way to deal with them is to
allow the leaves to decompose on the lawn. They contribute nutrients
and organic material as they decompose. Speed up the decomposition
process by running the mower over the leaves. The chopped leaves
disappear within a few weeks.
If you prefer to rake up the leaves, use them for mulch or in
the compost pile. The leaves are too valuable to bag and send
to the landfill. It is a double waste. The leaves contribute to
your landscape health and they take up valuable landfill space.
A layer of four inches of live oak leaves over the root zone
speeds up the growth rate of newly planted trees. Two to four
inches of mulch reduce the water needed for shrubs, perennials,
annuals, and vegetables. Live oak leaves are especially useful
as mulch because they are easy to spread and are attractive. If
after all my arguments you still do not want to use the leaves
in your landscape, find a neighbor that will use them.
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