A Guide to Pruning Protected Crops

Pruning is essential for keeping protected crops healthy & balanced through the winter months. Keep reading for some helpful tips on pruning greenhouse and hoophouse plants!

The following is an excerpt from The Greenhouse and Hoophouse Grower’s Handbook by Andrew Mefferd. It has been adapted for the web.

Unless otherwise noted, all photographs copyright © 2017 by Andrew Mefferd.

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Pruning Protected Crops

Though commonly practiced on all the vining/fruiting crops in protected agriculture, the goals and strategies for pruning are often misunderstood.

The best way to define pruning for protected agriculture is as a technique used to limit the amount and type of growth in order to keep plants balanced. Balanced plants will be more productive and healthier, with more predictable yields than those of unbalanced plants.

Understanding Plant Balance

Plant balance is best understood by considering what it means for a plant to be unbalanced. All of the vining crops in this book form a sucker at each node. If left to its own devices, a plant would develop a new vine at every single leaf.

Consider that every sucker would then begin producing a sucker itself at every node, and the number of heads would start to become problematic.

If a plant were allowed to develop an unlimited number of heads, its finite amount of energy would be divided among so many heads and fruits that growth and ripening would slow considerably.

I have seen this happen in indeterminate basket-weave tomato production, where ripening is noticeably slower and fruit size is smaller. With wide spacing this might not be as much of a problem, but when planted tightly in protected culture, unpruned indeterminate plants will branch out and compete with one another.

Pruning: What Does It Mean?

Pruning is one of the techniques that allows growers to crowd as many plants as possible into a finite area, by limiting each plant to the minimum amount of space it needs.

Pruning not only conserves space by preventing vines from branching out, but it also makes a plant more open and permits light and air to flow through the canopy.

This results in a minimal amount of yield reduction due to shading and disease. Fruit on pruned plants sizes up and ripens more quickly than on unpruned plants.

And all crops that are kept pruned are easier to harvest, because you don’t have to hunt through as much foliage to locate the fruit.

Changing Plants for Balance

Pruning allows you to change the plant to balance it to its ideal size.

For example, to grow a weak tomato variety over a long season, you might want to limit plants of that variety to only one vine, to focus all their energy up through the one stem, and hopefully keep it vigorous over the whole season.

If you grew the same weak variety grafted to a vigorous rootstock, you might be able to grow with two heads instead of one.

Growing indeterminate tomatoes unpruned in a basket weave is usually only possible in arid climates; in humid areas, the foliage is so dense that moisture builds up inside the plants’ canopy, which leaves them prone to foliar diseases.

Basics of Pruning