Mulches serve several purposes in the vegetable garden--protecting soil from drying in the sun and insulating it from frost, and decaying into valuable organic matter. Straw has the advantages of being relatively low in cost, easy to transport and easy to spread. As the by-product of the grain industry, it's readily available in most places.
Straw is the the dry stalks of wheat, rye, barley or other grains, the part of the plant left after the seeds have been removed. Each individual straw may be 6 to 12 inches long, depending on the type of grain that produced it and how it was processed. Straw is typically sold in compressed bales.
Since straw is used for animal bedding, the best place to look for bales is at a feed store or other livestock supply outlet. If you can't find one locally, call the nearest riding stable and ask where they get theirs. Another use for straw is for erosion control, so you might try phoning the highway department in your area.
Once removed from the bale, straw is light and fluffy, holding many air spaces that insulate the ground from sharp changes in temperature. This makes it also useful as a winter protection for tender plants. It's easy to spread by the armful or wheelbarrow load. Being a natural material, straw will eventually decay and add organic matter to the soil, but it is easily moved from one place to another for a year or two before it breaks up completely. It contains few weed seeds, though you may, for example, find grain sprouting between your lettuce plants.
Once wet, bales can be very heavy and the compacted straw may bind together into solid chunks. The long stems may be difficult to work into spaces between small plants, though some people put them through a shredder to create a finer mulch. The insulating properties of straw may work to your disadvantage if you cover cold spring soil with a thick layer, delaying the arrival of planting time for warm soil lovers like tomatoes. Broccoli, lettuce and peas, however, will thank you for it. Straw, like other mulches, can hide slugs and snails, so use a non-toxic, biodegradable product to get rid of these pests.
Best Ways To Use Straw
If you're making a new garden bed out of a part of your lawn, spread straw a foot thick over the area in the fall. By spring, the grass will be gone and the roots decayed, leaving the ground clear and easy to dig.
Use straw to mulch potatoes, adding more as the plants grow. This results in an easy-to-harvest mound of potatoes growing into the mulch.
Mulch peas, Swiss chard, cauliflower, cabbage, brussels sprouts, broccoli and other spring crops with straw to maintain a moist, cool root system.