Guide to pruning protected plants
Pruning is necessary to keep protected plants vigorous and balanced during the winter months. Read on for helpful tips on pruning your greenhouse and hoophouse plants!
Below is an excerpt The Greenhouse and Hoophouse Grower’s Handbook By Andrzej Mefferd. It has been adapted for apply on the Internet.
Unless otherwise noted, all photos are copyright © 2017 by Andrew Mefferd.
Pruning protected plants
While this is common practice for all vine/fruit crops in protected agriculture, Pruning goals and strategies are often misunderstood.
The best way to define pruning in protected agriculture is a technique used to limit the amount and type of growth in order to maintain plant balance. Balanced plants will be more productive and healthier, and yields will be more predictable than unbalanced plants.
Understanding plant balance
A plant’s balance is best understood by considering what it means for a plant to be out of balance. All vine crops described in this book form suckers at each node. If left to its own devices, the plant would produce a up-to-date vine on each leaf.
Consider that each sucker would then start producing a sucker at every node, and head count would start to become an issue.
If a plant were allowed to grow an unlimited number of heads, its finite amount of energy would be distributed among so many heads and fruits that growth and ripening would snail-paced significantly.
I have seen this in growing indeterminate basket tomatoes, where ripening is noticeably slower and fruit size is smaller. With huge spacing, this may not be as much of a problem, but unpruned, indeterminate plants planted tightly in a protected culture will branch and outcompete each other.
Pruning: what does it mean?
Figure 6.7. Botrytis enters the plant through the cutting wound. Notice the lattice clip that has been properly placed under the leaf before trimming it.
Pruning is one technique that allows growers to gather as many plants as possible in a finite arealimiting each plant to the minimum amount of space needed.
Pruning not only saves space by preventing vines from branching, but also saves space it makes the plant more open and allows featherlight and air to flow through the canopy.
This results in minimal yield reduction due to shade and disease. Fruits on pruned plants enlarge and ripen faster than those on unpruned plants.
AND all plants that are pruned are easier to harvestbecause you don’t have to search through as many leaves to locate the fruit.
Change plants for balance
Pruning allows you to alter the plant to balance it to the ideal size.
For example, to grow a tender variety of tomato for a long season, you can limit the plants of that variety to just one vine, focus all your energy on one stem, and hopefully keep it vigorous throughout the season.
If you grew the same tender variety grafted onto a sturdy rootstock, you may be able to grow with two heads instead of one.
Growing indeterminate tomatoes, unpruned in basket weave, is usually only possible in arid climates; in muggy areas, the leaves are so dense that moisture accumulates in the plant canopies, making them vulnerable to leaf diseases.
Pruning basics
Detailed information on pruning specific species can be found in the chapters devoted to individual crops. No matter what crop you are working on, it is always best to cut the part of the plant you are removing back to the living stem. Whenever you cut off part of a plant and leave a stub, the stub can rot back into the stem and infect the rest of the plant.
Morning is a good time to pruneespecially if you trim by snapping your hands. Plants are more tense in the morning and may break more easily than in the afternoon when they become more adaptable.
If pruning is done in the morning, the plants have the rest of the day to arid the woundswhich will assist them heal without infection. You can then spend an afternoon cultivating the trellis, as the plants are more adaptable as they transpire more vigorously and are easier to work with without breaking.
Trimming suckers
Figure 6.8. This tomato plant didn’t get sucked down in time, so the sucker is now as massive as it is competing with the main stem. You can tell that the main stem is on the left because it has a cluster of flowers on it. The sucker on the right grew from a leaf node below the flower cluster.
Pruning goes hand in hand with trellising as a technique to allow your plants to grow the way you want them to.
In addition to opening the plant to facilitate featherlight transmission and air flow, maintains a balanced amount of leaves and fruits, which ensures constant plant growth and yields.
This may not seem like a massive deal, until you have a ton of fruit to sell one week and only half a ton the next.
If you don’t get it all off the first week and not enough the second week, you’ll start wishing you had picked up three-quarters of a ton in both weeks instead.
Pruning leaves
There are times when you will want to remove some of the mature leaves from most fruiting plants. In the case of tomatoes and eggplants, this operation is regularly performed under the fruit to raise air flow.
Increasing airflow will reduce disease and assist the fruit ripen faster by keeping it sultry.
Older leaves can be removed without harming the plant because they are in the shade and do not participate in photosynthesis.
Pruning flowering/fruiting clumps
All fruiting plants have a tendency to bear more fruit than they can ripen. Pruning flowering or fruiting clusters is done at some point with all fruiting plants to balance the amount of fruit with the amount of fruit the plant can actually support.
From time to time I see growers planting extensive crops of cucumbers in hoops or screen covers. But they could get a lot more out of the same size structure and fit a lot more cucumber plants in it if they put a little more work into the trellis.
It is much easier to pick cucumbers if you hold them above the ground rather than bending down and hunting among the leaves.
Trellis requires an initial investment of time to make subsequent work such as harvesting and pruning go more quickly. This goes hand in hand with pruning to keep your plants growing the way you want them to. It is also an investment in plant health and pristine, marketable fruit.