Cover crops for the Pacific Northwest

I have two raised garden beds (8 x 12 feet) in my back yard. Recently I read somewhere that having a cover crop during our wet winter months would help decrease the leaching of nutrients and would also help bind nitrogen in the soil.

Three suggested cover crops were crimson clover, Australian field peas (did they mean Austrian winter peas?), and vetch.

What would you suggest? Are these good recommendations? Which
might be the best?

Sustainable Horticulture: Today and Tomorrow (R. Poincelot, 2004, p.
372-377), says,

“Cover crops, when managed as green manures, can supply considerable nitrogen
for [vegetable] crops.”

Legumes, like the pea and vetch you mentioned are
good choices for increasing the nitrogen level in soils. (Hairy vetch, Vicia
villosa, and Austrian winter pea, Pisum arvense). Crimson clover (Trifolium
incarnatum) is almost as efficient at supplying nitrogen to the soil.

Hairy Vetch supplies 33-145 lb of nitrogen per acre/year to soil, Austrian
winter pea supplies 53-100 lb/acre/year, and Crimson clover supplies 19-114
lb/acre/year.

Another species you might consider as a cover crop is Fava bean (Vicia
faba), which supplies 25-105 lb/acre/year.

Additional information about growing cover crops in the Pacific Northwest
can be found on this information sheet from the Washington State University extension.

Territorial Seed Company, in Oregon, sells small quantities of cover
crop seed by mail order, including Hairy vetch, Crimson Clover, and Fava
Bean.

Cover crops, Legumes, Pisum, Sustainable horticulture, Trifolium, Vicia

when to plant peas

It’s already the middle of March and I’m worried that our soil is still too cold to plant peas (both edible and sweet). When is the correct time to plant them in the Seattle area?

Since weather patterns vary from year to year, it may make more sense to plant based on something other than the calendar date. An old adage says that it is time to plant peas when the lilac leaves are the size of a mouse’s ear. This may sound quaint, but it turns out that the growth cycle of the lilac (Syringa) is an excellent indicator of temperature. Phenology is the science concerned with the timing of specific biological events, and lilac is among the plants often studied. Project BudBurst has additional information about phenology and climate change. The U.S. National Phenology Network is also a good resource.

If you don’t have a lilac in your garden (or a mouse’s ear, for that matter), Washington State University Extension (link no longer available) says that a safe time for planting peas is usually mid-March, not so much because of soil temperature, but because in February the soil is often oversaturated, and your peas would rot in the ground.

removing sod and preparing soil for vegetable gardening

We plan to put in a vegetable garden next spring where we now have grass. It is a great sunny spot that we think would work well for this. The question is, after we cut out the sod this fall, someone has suggested we plant rye grass for the winter, is this a good solution? If not, what do we do to the soil this winter? (We plan to bring in some top soil after we take out the sod).

There are several approaches that you can use to get your new garden ready. One is from Growing Vegetables West of the Cascades by Steve Solomon. He
recommends removing the grass, covering it with no more than 1/2 inch of
completely rotted compost or 1 inch of raw ruminant manure, and spread
agricultural lime at 50 pounds per 1,000 square foot. Do this in early
October. Then scatter small-seeded fava bean seed at 6 to 8 pounds per
1,000 square feet. Rototill no more than 2 inches deep and relax until May.
In late May you rototill deeply and or spade in the overwintered garden
area. Then you can plant.

Another information source, Seattle Tilth’s Maritime Northwest Garden Guide,
recommends using an annual winter cover crop to improve the soil. It
suggests using 85% legume and 15% grain for maximum nitrogen fixation. For
the legume, you can use Field peas, Crimson clover, Fava beans or vetch. For
the grain you can use cereal rye, winter wheat, spelt or barley. Most of
these are applied at about 2 pounds per 1,000 square feet. Again you would
rototill or turn under the cover crop in late April or May.

Solomon’s method will provide a better total approach. You also should
consider having your soil tested to find out what is missing and what your
pH level is.

growing peas in the fall

I wonder why I’ve never known anyone who grows peas in the fall. I am an experienced gardener and have specialized in fall/winter vegetables. I am guessing the soil temperatures in the summer aren’t “friendly” to peas. I have some shelling pea seed that I think I’ll try, but wondered if you can find any information that will indicate how to be successful.

Your guess is a good one. Here is what Binda Colebrook says in Winter Gardening in the Maritime Northwest (Timber Press, 1998):
“It is theoretically possible to make a July sowing of peas and get a fall crop just before the fall frosts. The problem is that it is hard to keep these moisture-loving, cool-weather plants going through the rigors of the hottest part of summer. Even if you do manage this, there is a virus in the Northwest, called pea enation, that will cripple most varieties.”
Colebrook recommends seeking an enation-resistant variety, but further states that, having tried some of these resistant types, “so far I’d say it isn’t worth the trouble.”

Washington State University Extension doesn’t go into the specifics but you can read between the lines that a summer sowing will not result in a bumper crop of peas:
“Peas can be planted in early November for an early June crop. They may not make it every winter. Green peas and edible pod peas (sugar peas) can be planted until mid-July. A moderate harvest can be expected in fall.”

Note Westside Gardener’s blog post mention of the Alderman variety of shelling peas:
“The bad thing about older varieties of peas is they don’t have the disease resistance of newer types. Up here in the Maritime Pacific Northwest, two diseases seem to cause the most problems for pea growers. The first is powdery mildew, a non-specific fungus that we’re all familiar with. Powdery mildew often isn’t a killer though, and it can be controlled when necessary with wettable sulfur. A worse disease is Pea Enation Mosaic, which does kill non-resistant varieties. Enation is a virus which is spread by the Green Peach aphid, so controlling ranges from difficult to impossible (it only takes one aphid to infect a plant). Usually what happens is the weather warms up, and the aphids become active. Often this coincides with the peas starting to set pods heavily. When a plant becomes infected, it’s pods become warty-looking and rather woody. Soon after, the plants die. It can be very disappointing to have your plants all dry up just as you’re looking forward to harvest. As far as I know, there is no practical way to control enation. All of my favorite varieties, of course, are susceptible to Enation Mosaic.

When it comes to shelling peas, I still haven’t found anything to beat Alderman […] Some years I get a good harvest, while other years the vines are wiped out by Enation. The flavor is so good, though, that I find the gamble worthwhile. I am trying out a new pea this year, which is somewhat earlier than Alderman – Maxigolt […] Earlier maturity means it should yield more in those years enation strikes, but flavor will determine whether it unseats Alderman from its place in my garden.”