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Garden Plot: Timing your tomatoes - and other tomato tips

Friday - 5/4/2012, 10:37am  ET

Crushed eggshells provide calcium which can help ensure you'll get big, beautiful tomatoes. (Courtesy

Editor's note: Last chance to meet Mike this spring. On Saturday, May 5, Mike makes his final area appearance of the season to discuss "The seven secrets of successful organic gardeners" at 10 a.m. at a plant sale and fundraiser for the Moonflower Garden Club in Severna Park.

Mike McGrath,

Timing your tamatas

If you live in the District or in one of the region's more southern suburbs, tomato planting time can pretty much be here if you want, as your ten-day forecast shows the nighttime temperatures staying reliably in the 60s and high-50s.

But, the extended forecast also shows that some of our northern listeners still have nights in the very low-50s next week.

That's why you should always be suspicious of firm dates for doing any kind of garden thing "in the D.C. area" - it's just too big and climactically diverse a region to be pigeonholed like that. Instead, follow the golden rule for tomatoes and other tropical plants: Wait until May and then plant when nighttime temps are predicted to be 55 or higher for the next ten days.

Got plants in hand? Leave them out during the day and bring them back inside on chilly nights until planting time arrives.

Box plants on cold nights

What can you do if your tomatoes, peppers, eggplant and other cold-sensitive crops are already in the ground and a night in the 40s, or gulp, below the 40s, is predicted?

Easy. Just place a cardboard box over top of each tender plant before the sun goes down and lift the box off early the next day. The box will trap a little warm air around the plant, and - more importantly - prevent any frost from settling on those tender leaves, a real risk when temps are low, skies are clear and winds are light.

Don't worry about crops like lettuce, spinach, peas and broccoli. They love cool weather. But really worry about eggplant, peppers and tropical melons. They're even more cold sensitive than tomatoes, and should be the very last plants to be installed outdoors.

Eggshells will give you a perfectly pretty bottom

Every July and August, I get dozens of emails from listeners heartbroken that "a pest or disease is making my tomatoes turn black and rotten on the bottom just as they're getting ripe."

This is one of the only tomato problems that is not caused by a pest or disease. It's blossom end rot, which is a cultural problem, like opera. But unlike opera, there's a cure for blossom end rot: adequate soil calcium, which none of you have. So:

  • Crush up the dried shells of a dozen eggs and put them in each hole at planting time.
  • Or, dissolve a dozen calcium carbonate tablets in a watering can and slowly deliver that water directly to the root zone of each of your plants.
  • Or, use a natural plant food designed and specifically labeled for tomatoes. Organic tomato foods always supply lots of calcium, while chemical plant foods…well, they only supply more problems.

Are you determinate? Or indeterminate?

Yearning to grow your own tomatoes this year? Be sure to choose the right type for your situation.

If you're tight on space or have a container garden, stick to determinate varieties. These well-behaved tomatoes, which often have words like 'bush', 'pot', or 'patio' as part of their name, top out between three and five feet tall and are more naturally upright, although they are still vines, and need support. (Oh, and only one tomato plant per pot, container growers. Although, you can position smaller plants, like herbs and flowers around the edges of a big pot.)

INdeterminate varieties, on the other hand, have long, rangy vines that can easily grow ten feet in length over the course of a season and often produce very large fruits, like the popular beefsteak and treasured heirloom varieties. Don't try and grow a monster indeterminate like Brandywine or Mortgage Lifter in a tiny space or in a pot that doesn't look like it belongs outside a hotel. Each indeterminate plant needs at least a two foot wide footprint, at least a foot in between plants and serious support.

The best support for these big, delicious love apples? Buy a roll of real animal fencing (not chicken wire) or concrete reinforcing wire, cut it into six foot long sections, form the sections into cylinders, and then position them so that a compost-mulched tomato is in the center of each cage. Then drive a piece of rebar or a big metal stake through the side of the cage and into the ground. This stake is just to support the cage, NOT the vine. Don't stake the vine - you want it to be able to curl around the inside of the cage so that by the time it reaches the top, it'll have used up a good nine feet of its length.

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