“Happy plants make more resistant plants,” says Mathews. But what happens if a soilborne pathogen gains a foothold in your garden despite your precautions? Step one is diagnosing the problem—often the most difficult step. Start by checking in with a local master gardener group, cooperative extension, or agricultural university, to see what kind of diagnostic help they offer.
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“Once you have the diagnosis, then you can figure out what kind of measures you want to take,” says Nolan. “If it’s a soilborne organism that’s going to stay in your soil forever, like verticillium or nematodes, you can’t really get rid of it. If it’s something that goes away after a while, you can plant a different crop for a while.” Another option is solarization—using solar energy to heat the soil and kill pathogens—although that means covering your garden in plastic during the hottest months instead of growing the heirloom tomatoes you love.
Related: Grow Healthy Plants From Seedlings Every Time
Even if you cannot figure out what, exactly, infected your plants, you can still take measures to help ward off future problems. If a plant dies, says Mathews, pull it out and look at the roots. Roots that are dark brown, black, slimy, or mushy show classic symptoms of root rot. If the plant was in a container, discard the soil in the trash—not the compost pile. If the plant was in the ground, toss out the entire plant and its root ball, plus at least 4 inches of soil from around the plant.
As Nolan says, “Be aware of what kind of soilborne pathogens your plant may get. Knowledge is power—it helps you avoid things.”