For best results, don’t rush to plant tomatoes

As I stood on the set of KDKA’s “Pittsburgh Today Live” show, I spotted actress Mariel Hemingway, who was on the show next, standing off camera watching me warn gardeners about planting tomatoes, peppers and other tender crops too early.

As I finished, something surprising happened — a celebrity was walking toward me, with a beaming smile intent on actually speaking with me. We laughed about the climate in Los Angeles, where her tomatoes and peppers were already in the ground at the organic garden she tends. In an instant, I wasn’t talking to a famous actress, I was chatting with another gardener. It’s one of the things I love about gardening — it transcends so many boundaries.

One of the things we all have in common, whether movie stars or not, is the need to grow healthy, homegrown tomatoes. It’s a little easier in L.A., but it would be hard to argue that the tomatoes grown in our climate aren’t the best-tasting in the nation.

I’ll be planting a few tomato plants this weekend, but the main crop will wait. Mom said tomatoes should be planted on Memorial Day, and Mom is always right. This weekend’s planting might still need to be covered if the weather turns cold again.

I have to bite my tongue when I see people filling their shopping cart with tender plants in mid-May with the intention of getting them all into the cold spring ground.

For the past few seasons, gardeners have been battling fungal issues with tomatoes. A cool, wet spring creates the perfect storm for the disease. Last season, it started raining in April and didn’t stop until June. We just never know what the weather will be; that’s the fun of gardening.

One thing that helps tomatoes thrive is warming up the garden soil. One way to do that is to cover the bed with black landscape fabric a week or two before planting. Another trick is to use a product called Wall-O-Water. It’s a free-standing plant protector filled with water. Put these out in advance of planting to heat up the soil and also create an individual greenhouse for each seedling.

Planting

The first thing to do when planting is immediately add a layer of mulch. This stops the soil-borne spores of early blight and septoria leaf spot from splashing up on the bottom leaves. Both diseases usually enter the plant’s system from those bottom leaves, turning them yellow and working its way up the plant. They usually don’t kill the plant but can reduce production dramatically. I like to remove the bottom leaves too, making it harder for the spores to reach the plant.

Tomatoes will thrive when the planting hole is filled with compost; the soil amendment gives the plants everything they need for the season. When plants are growing strong, they fight off pests and diseases better.

Spacing

Give the plants plenty of space, at least 3 feet for full-sized, vining varieties. They also need support in the form of staking or caging. Don’t bother with a little 3-foot-tall cage seen at some stores; the tomato will outgrow it by June. In my garden, each plant is surrounded by a 5-foot cage made of concrete reinforcing wire. It can be found at hardware stores and is available in rolls.

Mine are cut in 5-foot lengths with lineman’s pliers and are then made into the cylindrical cage. They are put in place the day the tomatoes are planted, with the cage attached to a stake pounded into the ground. The stake stops the cage from toppling at the end of the season when the tomato plants have become huge and are flopping over the top.

If staking is for you, just be sure to get into the garden every week or so, prune the plant to one central leader and keep tying the vine to the stake as it grows. If you miss a week, you’ll be wrestling with an unwieldy rampant vine or two.

Succession planting

The No. 1 thing I do to prevent fungal diseases is succession planting. I learned about it by accident through a variety called ‘Sungold.’ It’s my wife’s favorite tomato, which makes it crucial to the garden. The plant produces loads of extremely sweet, orange cherry tomatoes.

One year, I was going to be picking on June 15 and was bragging about my early harvest to my garden friends. Mother Nature taught me a lesson by dropping a huge black cherry tree on my three ‘Sungolds’ during a summer thunderstorm. You would have thought a baby was trapped under there, as I frantically cut away at the tree with my chainsaw. It was all for naught, though, as the plants couldn’t be saved.

I had two leftovers in the greenhouse planted in 6-inch pots, and even though they looked a little leggy and tired, those ‘Sungold’ plants loved the warm soil and air temperatures. I had never planted that late before, and at the end of the season my main crop, planted May 15, was succumbing to fungal diseases. The two leftovers had no signs of disease. The plants all had the same weather from June 15 on, but the leftovers were snug and warm in the greenhouse early on.

Planting everything the same day is a way of putting all your eggs in one basket. Now I stagger the plantings. Some tomatoes go in May 20, then more on May 30 and so on, all the way to July 4. The last planting is something like ‘Early Girl’ or a cherry tomato like ‘Sungold’; both will put on tomatoes quickly and will be ready to harvest at the end of the season.

That valuable lesson of succession planting has been expanded in my garden to most crops, including peppers, cucumbers, cool-weather crops and more. It means that some of these plants are growing off the cycle of certain pests and diseases, which can make all the difference in the world.

Disease control

If the plants show signs of one of the early diseases, Serenade is a great organic fungicide that works as a biological control. It stops the fungal spores from reproducing and is safe for the environment.

Another tip is to grow lots of types of tomatoes, as each one reacts differently to diseases.

There’s one disease called late blight that is fatal to tomatoes. It’s not that common but hit Western Pennsylvania hard about eight years ago. Late blight often starts at the top of the plant; stems and fruit will have brownish, black lesions on them. There’s no cure, but before plants are removed from the garden, be sure to have the disease properly diagnosed. Send a picture to me or your local nursery. Don’t bring any plants to the garden center; this disease can spread fast. If it’s late blight, the plants need to be bagged or burned.

Whether it’s six tomato plants next to the garage or a field of vines, every gardener knows there’s nothing that can compare to a homegrown fruit enjoyed warm, right from the plant.

Doug Oster is the Tribune-Review home and garden editor. Reach him at 412-965-3278 or doster@tribweb.com. See other stories, blogs, videos and more at triblive.com/lifestyles/dougoster.