Clothe your soil: Cover crops help en­rich it

The Progress-Index - At Home - - GARDENING - By Lee Re­ich

Cover crops are plants that gar­den­ers and farm­ers have, since the begin­nings of agri­cul­ture, grown not to eat but for the good of the soil.

Blan­ket­ing the ground to hold soil par­ti­cles in place, a cover crop pre­vents the ero­sive ef­fects of wind and wa­ter. It helps nour­ish plants by pulling up nu­tri­ents from deep in the soil and ni­tro­gen from the air.

Our fore­bears also ap­pre­ci­ated how a cover crop could sup­press weeds by shad­ing them out and even, in the case of crops such as rye and oats, by re­leas­ing nat­u­ral, weed-sup­press­ing chem­i­cals into the soil. Or­ganic mat­ter is at the heart of good gar­den­ing, and cover crops pro­vide that or­ganic mat­ter, grown in place, so you don't have to buy and spread other or­ganic ma­te­ri­als, such as com­post, straw or leaves.

Cover crop re­al­ity check

But where do you put cover crops when you al­ready have a full gar­den?

There's room. In a veg­etable or an­nual flower gar­den, you might plant cover crops to­ward the end of the sea­son as space be­comes avail­able. Or a dif­fer­ent part of the gar­den might be set aside each year for a whole sea­son's growth of some cover crop.

Cover crops also could be planted in among peren­ni­als and shrubs to grow for part of the sea­son. The right cover crop might even look dec­o­ra­tive among (other) or­na­men­tal plants. Crim­son clover, for ex­am­ple, puts on such a spec­tac­u­lar show — its blos­soms clus­tered tightly like straw­berry pop­si­cles on up­right stalks — that you'd hardly sus­pect it was im­prov­ing the soil.

Plants to use

Plants in the grass or legume fam­ily are com­monly used as cover crops. Grasses are val­ued for their ex­ten­sive roots,

which "plow" through the soil. Once those roots die, they be­come valu­able or­ganic mat­ter — lots of it. For ex­am­ple, 385 miles of roots have been es­ti­mated to lie be­neath a sin­gle rye plant! Legumes' roots are less ex­ten­sive, but har­bor micro­organ­isms that en­rich the soil with ni­tro­gen taken from the air.

Some species or va­ri­eties of grasses or legumes are bet­ter adapted to drier sites, some to wet­ter ones, and some to less or more fer­tile soils. Also con­sider when the cover crop will be planted: Cool-weather ones are best for the end of the sea­son in the North or dur­ing win­ter in the South; warm-weather cover crops are for sum­mers ev­ery­where.

One com­monly used sum­mer cover crop is buck­wheat, which is nei­ther a legume nor a grass. (It's re­lated to rhubarb.)

Seeds for cover crops are avail­able at feed stores, and some­times at gar­den cen­ters.


How do you deal with cover crops once they have served their pur­pose? An­nual plants even­tu­ally flop down dead on the ground — but not nec­es­sar­ily at an opportune time.

Till­ing is the usual op­tion, but is dis­rup­tive to the soil and "burns" up much of the or­ganic mat­ter that the cover crop might have added.

Sim­plest, of course, is to grow some­thing that dies by it­self at the right time. In my veg­etable gar­den, I plant oats and field peas in any beds that be­come free of veg­eta­bles be­fore the end of Septem­ber. The oats and peas thrive in the cool weather un­til win­ter, when they die from the cold.

An­nual cover crops not killed by win­ter might be mowed to bring on pre­ma­ture death. This is usu­ally done just be­fore the plant is get­ting ready to flower. Two or three mow­ings might be re­quired for some cover crops, such as rye grain.

In­no­va­tive strate­gies for us­ing cover crops more ef­fec­tively and with less fuss are on the hori­zon. For ex­am­ple, an an­nual cover crop like subter­ranean clover bears seeds in spring that lie dor­mant, not sprout­ing un­til the end of sum­mer. Ideally, you'd plant it once and then it would self-plant at the right time an­nu­ally there­after. Another pos­si­bil­ity is peren­nial cover crops that are not overly com­pet­i­tive or that are suf­fi­ciently weak­ened by mow­ing so that they could be grown along­side crop plants.

There are many ways to use a cover crop on your own "back 40." Take the time to study spe­cific plants, and then experiment.

Do con­sider plant­ing a cover crop rather than leav­ing the soil bare. Bare soil even­tu­ally be­comes clothed with a nat­u­ral, less prefer­able cover crop: weeds.


This cover crop is or­na­men­tal, even as it im­proves the soil in flower beds at Chan­ti­cleer Gar­dens in Wayne, Pa.

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