New Tips for Growing Tomatoes

This past weekend, I had a chance to attend the Gardening Expo in Madison, Wis. This is a hugely popular event with gardeners in our neighboring state. One of the standing-room-only crowds was for a presentation on growing tomatoes given by Joey and Holly Baird of the Wisconsin Vegetable Gardener website. The Bairds grow more than 100 tomato plants each year, and have created more than 1,000 videos about vegetable gardening and canning. They know their tomatoes!

We have our own tomato expert at MSHS and I’ve learned a lot from him. (You can, too, by checking out this series on starting and growing tomatoes — part 1, part 2, part 3.) But a couple of the tips from the Bairds were new to me, so I thought I’d pass them on.

  • Do not plant tomatoes until the soil at root zone is 55 degrees. Every gardener wants to get their tomatoes into the ground early, but you cannot rush it. If you do, the plants will just sit there. The Bairds recommend you take the temperature of your soil where the roots will be before planting. You can use a special soil thermometer or even a meat thermometer to check the temp.
  • Use corn meal to prevent early blight. Early blight is a fungus that overwinters in the soil and infects tomatoes through the leaves. A sign of infection is yellowing, withered leaves at the bottom of the plant. The Bairds recommend spreading a handful of whole grain, yellow cornmeal around the base of each tomato transplant when it is planted. The cornmeal provides a barrier between the plant and the fungus in the soil. On its own, this method is 80 to 90 percent effective, the Bairds said, but if combined with trimming leaves off the bottom 6 to 8 inches of the tomato plant, it’s nearly 100 percent effective. This makes sense to me because I’ve used corn gluten meal as a weed-and-feed on my lawn in the past, and found that it seemed to create a barrier that prevented weed seeds from germinating. I’m going to try this one this year.
  • The ideal fertilizer for tomatoes is roughly 5-5-5. If you look at every fertilizer package, you see the levels of nitrogen-phosphorus-potassium in the fertilizer. Tomatoes need nutrients, but not a heavy load, which would mostly result in excess foliage. The Bairds recommended Sustane, which is a Minnesota-based company, that uses turkey droppings and pine bark to create an organic 4-6-4 blend — just about perfect for tomatoes.
  • Plant tomatoes 2 feet apart and stake immediately. Try the Florida weave. This isn’t hugely new — tomatoes need room to grow and both vining and bush tomatoes benefit from staking. The Bairds recommended a method I had not heard of before called the Florida weave.  This involves setting stakes in the ground at the end of a row of tomatoes and between each tomato, then as the tomatoes grow, weaving twine around them to hold them upright.
  • Can you spot the hornworm? He’s the one eating.

    To get rid of hornworms, feed the birds. Hornworms can be devastating to tomato crops, and those little stinkers can hide on tomato plants very well. The Bairds were beset with hornworms, then they set bird feeders out near their garden. Pretty soon, no hornworms. Apparently birds can find them much easier than humans.

I love hearing new tips for gardening! March is the month for many garden expos, hort days and other events filled with garden information. Check out the Calendar of Events on the MSHS website for an event near you.


  1. Dave Knapp, UMN Master Gardener and Master Naturalist on February 15, 2018 at 7:43 pm

    I agree with the tip regarding temperature and this is a frequent mistake of home gardeners (planting too early).

    I kept looking for an explanation as to why Yellow Corn Meal would be effective against Early Blight Fungi. It seems the true message is that a “barrier” to deter over-wintering spores is the deterent, not that it should be Corn Meal. Nothing in the tip says Corn Meal does anything more than a paper barrier might.

    Wasps also may be responsible for disappearing horn worms.

    • Mary Lahr Schier on February 16, 2018 at 5:39 pm

      Thanks for the insight, Dave! I may test cornmeal vs. paper this summer to see if there is any added benefit to the cornmeal. I did not mention it in the post, but the Bairds discussed the parasitic wasp that preys on hornworms, too.

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