Originally appeared in the Monterey Herald and the Santa Cruz GT Weekly
Rest and rejuvenation for your weary soil, green manure gives back in spades
The transition between summer and fall is always been an especially acute time for vegetable gardeners. Not only must we reacquaint ourselves with store-bought tomatoes that taste like gopher fur dipped in wood shavings, but we must also adapt to all the extra time on our hands as our garden beds lay fallow. There is, after all, nothing worse than a gaggle of gardener’s wearing overalls and floppy hats, fondling their hoes outside a 7-11 and asking strangers for a spare, heirloom tomato.
But as any good organic gardener knows, late summer/early fall is time to sow the cover crop. Often called green manure, cover crops have been around before the invention of the “green” light bulb, or for that matter, before “green” meant something other than the color of plants, grass and trees. Organic gardeners have long touted the benefits of green manure with the same zeal of growing their own vegetables. And they know that the two have a symbiosis that works magic in the garden.
But your average vegetable gardener—myself included—took longer to make the connection. Why grow something that you’re not going to eat or pick? Instead, I’d pull the last of the summer’s cornucopia from the garden and leave the garden to the weeds for next season. My soil hated me for it and over time, repaid me with ever-dwindling crops. Reap what you shall sow.
Green manure, then, is nothing short of a philanthropic uncle that invests in your garden’s future. Cover crops—especially plants in the pea and bean family—fix valuable nutrients like nitrogen that your vegetables were all too happy to consume. Additionally, they act like a living mulch, enthusiastically competing with weeds for space and sunlight while their alive, suppressing weeds when their dead—which goes by the militant-sounding term “crop cover smother effect.” Green manure also protects from erosion when it rains, providing an umbrella over the soil and allowing the rain to seep slowly into the dirt. Making the soil more drought resistant, cover crop roots also increase the water retention capacity of soil.
Much in the way cover crops suppress weeds, they stop disease cycles in their tracks by reducing bacterial and fungal diseases that eventually make their way to the summer crops. Mustards are particularly good contenders for this, and along with vetch and clover, attract beneficial insects to the garden. Cover crops also break up the soil with their roots making them a spade-free gardening method that any lazy gardener (again, like myself) will appreciate.
“Our radish mix is like a soil buster,” says Greg Lightfoot of Peaceful Valley Farm Supply, a good Online source for cover crop seeds. Lightfoot has been gardening organically for the last 35 years and says certain cover crops can punch through heavy clay “like vegetable jackhammers.”
Cover crops are best planted at least a month before the first threat of frost. In other words, Right Now. If you still have vestiges of the summer garden, plant between the rows. Though cover crops prefer a cool season, there must be enough warmth for the seeds to germinate.
For best results combine various cover crops. A brawny combo for a soil workout includes a mix of purple vetch, fava beans, winter wheat and cereal rye. Vetch and fava beans pour nitrogen into the soil and create a huge amount of biomass that can either be composted or tilled right into the beds. Be sure to harvest both before they go to seed otherwise nitrogen drains from their root nodules. Rye and wheat on the other hand create super fine root mass which aerates the soil nicely and dumps nutrients in time for spring planting.
With the cover crop safely in the ground a gardener can
finally relax and peruse a seed catalog by the fire, dreaming fondly of next
summer’s fresh vegetables. All this while outside, in the cold winter ground,
the soil is in good hands, being nourished and protected by nature’s own green
cover up.
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