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In the Garden: Well-timed pruning helps boost tomato harvest

A late-season pruning regimen will ensure the best possible tomato harvest. (Susan Mulvihill/For The Spokesman-Review)
A late-season pruning regimen will ensure the best possible tomato harvest. (Susan Mulvihill/For The Spokesman-Review)

Every summer, I always look forward to biting into that first ripe tomato. It’s a well-known fact that a grocery store tomato cannot begin to compete with a sun-ripened, full-flavored tomato.

In my garden, I have learned a lot over the years about what I can do to ensure the best possible harvest – and it all starts from day one.

I used to start my plants from seed in February until I realized that was way too early. The plants would be leggy and weak by the time it was safe to plant them out in the garden. After much experimentation over the past few years, I’ve determined that – for my zone 5 garden – the first of April is the ideal time to get them going. I know that sounds really late but, by planting time, the plants are a good size and haven’t been set back by being stuck in a pot for longer than is ideal.

Prior to planting them out in the garden, I cover the tomato bed with a sheet of red plastic mulch. Also referred to as “tomato mulch,” it increases the temperature of the soil which is something warm-season crops prefer.

On planting day, I remove the lower leaves and plant the seedlings deeply to encourage additional root growth along the main stem. I also provide the plants with a wire support to keep the foliage and fruit off the ground for good air circulation. A drip irrigation system – underneath the plastic mulch – provides water at the soil surface, right where the shallow roots can get to it; overhead watering of tomato plants is not ideal as it can spread disease on the leaves.

As the plants grow, the only pruning I do is to remove any low branches that are resting on the ground. I do not remove suckers because that dramatically reduces the tomato-producing potential for each plant.

Each year in early August, I begin my tomato-pruning routine to get as many ripe tomatoes as possible before the fall frosts arrive.

I liken this first pruning to getting a haircut. The goal is to trim back some of the long, unruly branches. Knowing that new flowers will never mature into ripe tomatoes in time, I want to focus the plants’ energy on ripening the existing tomatoes.

The second pruning takes place near the end of August and it is more severe than the previous one. If there are any new stalks that came up as a result of the first pruning, trim those off first. Next, trim each branch right above any tomatoes that are close to a mature size to encourage them to ripen by the end of the season.

The final part of my tomato-ripening routine takes place in early September. What I do might sound mean but the goal is to stress the plants so they finish ripening the majority of the remaining tomatoes.

First, I turn off the water to the bed. Then I use a shovel and cut straight down through about a third of the roots, 10 inches out from the plant’s main stalk. You’ll be amazed at how quickly those last tomatoes start ripening.

If there are still green tomatoes by frost time, I pick them, take them indoors and place them in a dark area between sheets of newspaper. They will quickly ripen, extending the harvest of my favorite crop.

Susan Mulvihill is co-author, with Pat Munts, of “Northwest Gardener’s Handbook.” Contact her at Susan@susansinthegarden.com. Watch this week’s “Everyone Can Grow A Garden” video on youtube.com/c/susansinthe garden.


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