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Tomato Season Update: Pruning Suckers and Poor Production


You Bet Your Garden
Question of the Week © 2018 Mike McGrath

Note: Hundreds of Mike's informative articles are available (in alphabetical order!) right here at the Gardens Alive website. To find Mike's answers to your specific garden problem, Click here and find your topic (like Weeds, Worms, Rhododendrons...) in our complete alphabetical archive of Questions of the Week.

Tomato Season Update: Pruning Suckers and Poor Production

Q. I'm getting my garden plans together and was wondering if you recommend pruning the shoots that grow from leaf nodes on tomatoes? I've heard that doing so will limit production but allow better circulation of air and may help with fungus issues. What's your feeling about this?

---Hank in Ambler, PA

A. My feeling is one of congratulations for a question well-asked! This is the first time anyone has suggested a logical reason for pruning tomato plants instead of just believing that removing green leaves from a plant will somehow magically make more fruits!

Now: In the past, I have always said that the only 'suckers' on tomato plants are the people doing the pruning. Have I changed my mind?

No; I've never removed a healthy leaf from a tomato plant. But I applaud Hank's thinking here; the issue of airflow to prevent disease is a legit one. However, I like old-fashioned passive airflow; you'll always get more tomatoes by spacing the plants a little further apart than you might like than by any removal of healthy leaves.

I specifically recommend a two-square-foot 'footprint' for each plant with a foot of open space in between. This is where my famous tomato cage design comes in really handy, as it confines even the most rampant varieties to an area that's within an inch or two square feet.

But what does it mean for airflow when a twelve-foot high heirloom is curled up inside a five or six-foot-high cage? Aren't the leaves crowded together? Yes, but in my experience, it doesn't lead to anywhere near the disease issues that crowding plants together does.

And I have plenty of experience with potential disease issues because I (perhaps foolishly) bought Snow White's old house in the woods. It's nice when the chipmunks and birds come in to help with the dishes, but the abundant trees on Snow's old landscape are not kind to sun-loving plants. I have been growing tomatoes in these less-than-ideal conditions for the past 30 years and have consistently found that space between plants is the best disease prevention strategy, even if the individual plants are a little crowded inside their cages (and in my case, squeaking by with the minimum amount of sun).

So no pruning. Certainly not on determinate varieties—the well-behaved types that top out at five or six feet high. Determinate varieties have a very low 'leaf-to-fruit ratio' to begin with and need every green leaf to keep good flavor in the picture. But with indeterminate varieties—you know; those ill-mannered but incredible tasty types that grow on ginormously never-ending vines…

…no pruning of healthy leaves either!

But you should remove every discolored leaf immediately. For one really important and two secondary reasons.

The secondaries:
  1) Because a discolored leaf is no longer photosynthesizing and can't provide any benefit to the plant; and
  2) it could be diseased and removing it promptly will help prevent the spread of that disease.

But THE most important reason to remove discolored leaves promptly is so that your garden looks better than your neighbors' gardens and makes them jealous. They're not going to realize that you have 20 percent fewer leaves than they do! They're just going to (enviously) see that you don't have any nasty looking ones.

"It is not enough to succeed; others must fail".

Next question!

Q. We have two 4' x 4' raised beds built over hard pan; one is four inches deep and the other is six inches deep. The first year we grew tomatoes, peppers, onions and radishes in the beds and they all did well. The second year we let the soil rest after adding some organic compost. Last year (third year overall) we added more compost and tried tomatoes, peppers and onions. Onions did ok, but we had very little success with the tomatoes and peppers. Is there anything we can do to these beds, short of replacing all the soil, to have a productive season?

---Rick; professor emeritus at the Webb Institute in Glen Cove, New York

(Note from Mike here. Webb is a very prestigious Naval College that specializes in teaching ship design and construction. My nephew James graduated from Webb in 2004 and has worked in the ship building business ever since. And the main building at Webb is so amazing looking that it was used to 'play' Wayne Manor in the Val Kilmer Batman movie!)


A. OK. Now: 'Suddenly poor production' questions are among the hardest. But let's see what we can come up with.

A six-inch-high raised bed is better than flat earth, but twelve inches is better. However, the Professor says that peppers and tomatoes did well the first year, when the beds would have presumably been the shortest in height. Then he added what clearly sounds like bulk purchased compost two years in a row and tomatoes and peppers suddenly did poorly.

I suspect the soil.

I want The Prof to put some of this suspect soil into containers designed for growing plants and plant some pea and/or bean seeds in each one right now—indoors. Keep the containers well-watered and in a warm spot. Even inside, without artificial light, the young sprouts should initially be green and look well-formed. If they emerge light in color, off-color, or stunted, then odds are good that his compost was contaminated with herbicides. Which is tough darts, as modern herbicides (which typically enter the compost process via grass clippings) can persist in contaminated soil or compost for years.

But if this is the case, at least he won't waste another season growing in bad soil. And the answer to the obvious follow-up question here is to build new beds nearby and fill them with compost that passes what we call 'the duck test'*—it should look like rich black soil; it should smell a little earthy but not sweet or sour; and it should feel like good soil. And, of course, it should also pass the at-home herbicide test we just described…

(*a term originally coined for this purpose by Dr. Frank Gouin, a legendary compost specialist, now retired from the University of Maryland Extension system.)

…Which we are cleverly reminding people of just at the time they might be gearing up to buy bulk compost or topsoil for this season. (See this Previous Question of the Week for a longer discussion of bulk compost testing.)

The other possibility is that nearby plants have grown large over those two years and the good Professor now has too few hours of sunlight hitting those beds. Onions are reportedly growing well there, and they're a root crop, which can get by with fewer hours of sun. But fruiting plants like tomatoes and peppers really do need a solid six and preferably eight hours of direct sun a day, especially in northern locations like his New York area, where the season is short and somewhat chilly.

…Which brings to mind another possibility that also doubles as a timely tomato growing reminder. The soil in areas like Glen Cove generally stays cold long into the Spring, and rushing the season by putting hot-weather plants into cold soil can lead to bad behavior the rest of the season. Never plant by a date on the calendar. Always wait until nighttime temps are reliably in the fifties before putting tropical plants like peppers, tomatoes, melons and eggplant in the ground.

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