Is there a benefit to trimming the vines or leaves of a plant before the fruit ripens?
Question:
When the fruit of a vine plant, e.g., pumpkin or tomato, are forming, but are not yet ripe, does it help to trim “excess” vine or leaves, thinking that more energy will then flow to the fruit? I have done this with pumpkins, but am not sure I have noticed a benefit.
Does the increased sun exposure help ripen the fruit (squash, pumpkin, tomato)?
Is there any harm in trimming the vine or leaves?
Answer:
Jonathan Foster, Special Project Assistant
You are correct to suggest that growing/ripening fruits use a lot of the plant’s energy–in fact, because the plant has evolved to reproduce this way via seed growth and transmission, the plant will often preferentially reroute energy to this process. However, that energy is being produced through photosynthesis in the leaves, which are the “engine” of the plant. Removing them would actually decrease the amount of energy the plant has to work with, so I would not generally recommend trimming them.
There are three situations that offer exceptions. One, if the leaves or extra vine are showing signs of infection (with pumpkins, late in the season, this is often powdery mildew), it’s a good idea to remove the damaged tissue. Two, if your pumpkin vines are growing unruly and spreading beyond their space, it’s ok to trim the vine tips to slow things down, but I wouldn’t prune the foliage too hard because of the above reasons. Three, if a plant is actively producing new, green shoot growth, this also uses a lot of energy and can interfere with fruit production/ripening. For your example plants, this is most likely to occur in the suckers (the little leafy shoots that emerge from the axis between a branch and a stem) on tomato plants, and those should definitely be pinched out as soon as you see them. They will come off easily with a pair of snippers or with your fingernails, and they will come back every few days, so check the plant often.