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Q. What
are the best winter cover crops for home gardens in Pennsylvania? When
should they be planted? What should be done in the spring to kill
them or till them in?
A. Cover
crops are grown to protect the soil from erosion, and to be cut back
and tilled into the soil in spring to increase its organic matter
and nutrient content. They also help stimulate soil microbial
activity, shade out germinating weed seeds, and help loosen
compacted soil as their roots grow.
Winter rye is the most commonly grown winter cover crop in our area
because it is cold tolerant and can be sown as late as mid-October,
which gives gardeners time harvest annual vegetables and remove
spent annual flowers prior to planting. It is a winter annual grass
that will continue to grow until temperatures drop to about 40
degrees and resume growth when temperatures warm in spring. Winter
rye germinates quickly, and tolerates wet or dry conditions, low
fertility, and acid soils.
It secretes a substance that inhibits the growth of many weeds and
other plants, so it is important to mow it down and till it in about
four weeks prior to planting vegetables or flowers next spring. All
raw organic matter can tie up available soil nitrogen as it
decomposes and cause a temporary nitrogen deficiency in crops, so
working it into the soil early enough avoids that problem as well.
Winter rye produces a dense root system and lush foliage, so it can
be difficult to till under. It helps to mow it short prior to trying
to till it in. It may be easier to compost the clippings for later
application to garden beds, and till in the crowns and roots alone.
Certain legumes are often used as cover crops, but really provide
the most benefit if you plant them in spring and allow them to grow
all summer, which can take too much valuable space in a home garden.
Legumes are plants that have the unique ability to fix nitrogen from
the air in association with soil bacteria, and they return that
nitrogen when they are cut back and tilled into the soil. They also
have extensive root systems and are a good choice to break up hard,
compacted clay soils. Their best use in home gardens may be to start
new beds in places where the soil is less-than-ideal. Strip off the
sod, plant a cover crop of legumes, and allow them to grow for a
season before working them into the soil. Plant the desired crops
next year. Legumes used for cover crops include clovers, hairy
vetch, and alfalfa. Be sure to cut them back before they go to seed,
or some will make a nuisance of themselves.
To plant a winter rye cover crop, remove spent annual vegetables and
flowers from the garden. Till up the soil to prepare a good seedbed,
then broadcast the seed at two to two-and-a-half pounds per thousand
square feet. Rake it in lightly and water to start the germination
process.
LINKS
Composting for the
garden
Growing rhubarb
Garden
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