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Rotate Your Tomatoes to Avoid Wicked Wilts

Q. Tomatoes are the only vegetable/fruit I grow. I know I need to rotate them, but my garden is small and I have no place to rotate to. I use cover crops, a natural tomato fertilizer from Gardens Alive and compost—and most of my tomatoes do well, but the 'heritage' plants do not. Can you suggest anything other than rotating? Thanks.

    ---Bob in Eugene, Oregon.
A. "Heritage" is another way of saying "heirloom"—a variety that exists only because gardeners who loved it saved the seed from year to year, often passing it down as a 'family heirloom'. These varieties were treasured more for flavor and productivity than disease resistance. And because you mention your inability to rotate (a problem I've been having after getting out of bed in the morning), I presume you're having trouble with one of the soil-borne wilts: Verticillium (more common in cool climes) or fusarium (more prevalent in warm areas).

The first symptom of these dread diseases is what their common name implies—the affected plants wilt, especially on hot, sunny days. (ALL tomatoes will do this at the height of a grueling scorcher, but wilt-affected ones don't spring back up when the sun goes down the way a healthy plant will.) The lower leaves will turn yellow and eventually die, often falling off early in the season. The disease typically then progresses up the plant.

In mild cases, it only causes some lower leaf loss. Bad cases can kill the entire plant by mid-summer, especially if its a slow-growing determinate types. previo (See this Question of the Week for more info about determinate and indeterminate varieties.)

These diseases always catch up to tomatoes that are grown in the same spot year after year, and so rotation is defense #1. But many space-challenged gardeners are out of such options, and so turn to the next big tactic: Growing hybrids bred to be resistant to the wilts, identified by the letters V and F after their variety name on seed packets and plant tags. (Hybrids are natural plant crosses, NOT genetic engineering. They are perfectly natural and can be a big help for folks growing in challenging conditions and climes.)

Some heirloom varieties are also resistant. But they don't got no fancy letters, and so we have to rely on word of mouth to ID them. My 2002 book, "You Bet Your Tomatoes" (just reissued in a new edition by Plan White Press!), identifies Arkansas Traveler, Big Rainbow and German Johnson as having better disease resistance than most heirlooms. They're darned good tamatas too!

These soil-borne wilts aren't as linked to poor growing practices as the other 90 bazillion bad things that attack tomatoes, which explains why your seemingly excellent fertilization and soil-building work may not have been enough. Still, in addition to trying some rumored-to-be-resistant heirlooms, you should grow in raised beds, provide extra room between plants for exceptional airflow, keep a mulch of fresh, high-quality compost on the surface of the soil around your plants (the beneficial organisms in that Black Gold will help slow the progression of the wilts), avoid injuring the stems and roots of your plants, and remove any discolored leaves as soon as you see them.

You can also avoid the infested soil entirely by growing your heirlooms in big pots. And folks with some room to play with can kill the wilts completely in specific areas by solarizing that soil for a full season.

Q. Bad things happen when I plant my tomatoes in the same spot every year, and I can't play musical chairs, as I have a very small sunny area. You have recommended excavating as much of the old soil as possible and building raised beds filled with "good stuff". If I do this, must I replace the soil every year? (That's a lot of work!) Or can I keep using the same stuff year-to-year? You also recommend using a 'soil-free planting medium'. What the heck is that?

    ---Joe in scenic Mt. Laurel, NJ
A. Yes, Joe—if you're a flat grounder, get with the program and build those raised beds. (Click here for a previous Question of the Week with the basic details and directions.) Excavate as much of the old soil as possible, and build the new beds with a 50/50 mix of high quality yard waste compost and screened dark topsoil. This should protect your plants the first couple of years, as there won't be any disease in newly-purchased growing medium.

But you should still keep careful track of where you're planting, and try not to plant the following year's tomatoes exactly where the previous ones grew. (This is a wonderful added benefit of "adding crushed eggshells to the planting hole", as they take years to completely break down and are a great visual revelation that despite what you "think" about a spot having recently been tomato free, you are wrong, wrong, wrong.)

When you see signs that the wilt is building back up again, replace the soil with a freshly purchased 50/50 mix—or yes, compost and the soil-free mix that so perplexes you. Soil-free mixes contain only light, natural things like peat, perlite, vermiculite and compost or composted forest products; no 'dirt'. They're what you SHOULD be using in those containers; hint, hint! (Read this previous Question of the Week for lots more details on successful container gardening.)

Q. We've grown tomatoes in raised beds for the last three years and our sins have caught up with us in the form of wilt. Are there any plants we could grow that naturally inhibit the wilt? Thanks.

    ---Beth in Titusville, NJ
A. Maybe broccoli, of all things. Back when I was Editor-in-Chief, ORGANIC GARDENING magazine reported that researchers from the University of California at Davis had great success controlling verticillium wilt by tilling broccoli resides into the soil before planting. (And yes, you have to till it in. Despite the hopes and wishes of all you 'companion planters', no plant can do good things for another plant simply by growing next to it.)

Their suggestion for gardeners interested in replicating their work was to till one cubic foot of dried or fresh ground-up broccoli stems or leaves into every 100 square feet of soil prior to planting. Don't waste the nutritious florets on this; just the stuff you wouldn't be eating anyway.

The researchers also proposed a succession-planting scheme, where you would grow broccoli in the Fall or Spring, harvest the heads in the late Spring and then till the plants into the soil before your tamata planting. Sounds really cool. If anyone out there gives either version a try, let us know how it works.

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