Nematodes are the biggest garden problem you'll never see. What you will see is the injury these tiny wormlike creatures cause.
Common signs of nematode injury include yellowing leaves and wilting, even when the soil is moist. They milk you of yield and can cost in unnecessary soil amendments or chemical treatments as you try to guess what's wrong with your garden. Nematodes can kill plants too.
To deal with nematodes, the first step is simply to be sure you've got them. This requires a soil test (see "Test your soil").
They are virtually impossible to eliminate, but you can learn to garden around them. If you had nematodes in your garden this past year, here are some things you can do to have more success next year.
DON'T FEED THE NEMATODES. Research shows nematode levels are lower if you rotate crops from one area of the garden to another. Root knot nematodes seem to favor tomatoes, okra, beans, squash, peppers, carrots, cucumbers, muskmelons, eggplant and watermelons.
Crops that have partial built-in resistance to the root knot nematode include broccoli, brussels sprouts, mustard, chives, cress, garlic, leeks and rutabagas.
Root crops are susceptible to nematode damage and should not be planted in the same garden area year after year.
MOVE THE GARDEN. It may seem extreme, but if over the years you've built up high levels of nematodes in your soil, moving the garden to another location might be a good idea. If this new area also has nematodes present (which is highly likely), don't continually plant crops that tend to increase the nematode population.
GET NEMATODE-RESISTANT VARIETIES. These vegetable varieties usually have the letter N on the seed packet. Tomatoes now come in several nematode-resistant forms. Resistance does not mean total suppression though. You will still have the nematodes, even if you plant a resistant crop.
PLANT EARLY. Nematodes seem to be at their worst as soil temperatures rise. So plant early crops like lettuce, onions and radishes before nematode activity picks up again.
DESTROY ROOTS AT SEASON'S END. Plant roots provide nematodes a place to feed and reproduce well into the fall and winter. As you pull up your garden, don't put root matter in your compost pile.
ADD ORGANIC MATTER TO THE GARDEN. More organic matter means more microbes actively feeding in the soil, some of which can lower nematode levels. Some gardeners plant what is called a green manure crop to build up organic matter. This is usually a legume, clover, vetch or rye crop that is tilled into the soil before planting.