Should You Prune Pepper Seedlings?

Pinching and topping refers to the removal of the top part of a plant. Pinching peppers results in more side branches and a bushier plant which, it is claimed, leads to more fruit and a higher yield. Is this true? Should you pinch pepper plants?

Some people also suggest removing the first bloom to allow the seedling to grow larger and develop a better root system. Does this really happen? Does it increase yield. Should you pinch the first bloom?

There are lots of opinions online and in blog posts, but I found none that actually presented any scientific evidence for their suggestions. What does science say?

How Do Pepper Plants Grow?

Pepper seedlings tend to grow with a single leader forming one main stem. When the top is pinched off, the two dormant buds located on the remaining upper leaf axils will start to grow, forming two new main stems and each of these can produce peppers. Pinching definitely produces shorter, bushy plants.

Peppers used for food include 5 different species and thousands of cultivars. Their branching habits can be different and pinching will affect different cultivars differently.

Does Pruning Produce a Bigger Root System?

I found very little evidence that pruning results in a larger root system but most studies focus on yield – not root growth. Removing flowers or early fruit should allow a plant to focus growth on more leaves and more roots.

Does Pinching Produce a Higher Yield?

Pinching does produce more branches and these can produce more blooms, which result in more peppers. However, that does not necessarily mean you get a better yield because yield is measured different ways. It can be the total weight of peppers, or the weight of ripe peppers before the end of the season, or even the number of peppers produced.

In one study 14 pepper varieties were tested for different degrees of pruning (2,3 and 4 stems). Peppers were grown in pots in an unheated glasshouse during spring. Pruning reduced the number of fruit per plant as well as overall yield.

Another greenhouse study looked at three hybrid bell pepper cultivars: ‘Pasodoble’, ‘Lirica’ and ‘Sondela’. Plants pruned to one branch resulted in a significant increase in early yield, fruit size and internal fruit quality over plants pruned to two branches. However, plants pruned to four branches produced the highest yield, due to a higher number of fruits per plant. The best fruit number and total yield were obtained by pruning ‘Pasodoble’ plants to 4 branches and pruning ‘Lirica’ plants to one branch, clearly showing that pruning effects depend on cultivar.

Pinching chili peppers grown in a field (subtropical climate) resulted in shorter plants, a higher yield (not defined) and delayed fruiting. Double pinching about 15 days apart produced an even better yield than single pinching.

Pruning habanero peppers (Capsicum chinense) to 2 or 3 stems produced a higher number of first quality fruit than no pruning at all. It is not clear if the pruning started at the seedling stage or was done later.

Age of seedlings may also play a role. Eleven week old seedlings produced a higher yield after pruning in one year, but a lower yield the second year of testing. Eight week old seedlings that were unpruned produced a higher number of green bell peppers as well as a higher weight, in both test years. Pruning at the right time could be critical to getting a higher yield.

Does pinching produce a higher yield? Maybe.

Pinching definitely delays production of early fruit. Pinching may produce a higher yield or it might not. The effect depends on the cultivar, growing conditions, and the season length. It might also depend on the age of the seedling at time of pruning. This variability may explain why gardeners report a wide range of results.

Will Removing Blooms Increase Yield?

Here is the common advice on the internet, “pinch first blooms to get the plants to put more energy into growing rather than into early fruit. Removing blooms is especially effective if done prior to transplanting, as the plants will put more energy into their roots and leaves rather than producing fruit”.

Removing flowers or the small fruits soon after they set will have the same effect.

A plant, especially a young one, produces a certain amount of food which is used to grow the plant bigger. This food reserve is under the control of the plant and is shared between root growth, leaf growth and fruits. It generally won’t produce flowers until its food reserve is large enough to support the subsequent fruit which means that removing flowers is not a requirement for growing healthy plants. If the plant is ready to fruit and the flowers are removed, the plant will just form new flowers which requires extra energy reserves, possibly slowing down growth.

Pinching off flowers at transplant time can be beneficial to the plant if there was a lot of root disturbance during planting, or if it suffered leaf damage while being hardened off. But if you transplant carefully, there is no reason to remove flowers while transplanting.

One research paper commented that “Although some producers already remove the flower that appears on the first branch of green peppers, flower thinning has been poorly studied and more scientific information on the subject is necessary”. If science needs more study how is it that gardeners know the answers?

This same research group measured marketable, and unmarketable yield; mean marketable and unmarketable weight, and mean length and width of marketable fruits and found flower thinning had no effect on the two green pepper varieties they tested. They don’t recommend flower thinning.

Pruning off the first two or four fruits of sweet peppers grown hydroponically under shade cloth produced no significant effect on yield (fruit number, fruit mass, unmarketable yield, marketable yield and total yield).

A paper detailing the method for commercial greenhouse production says, “The primary goal is to establish the young pepper plants in the media and ensure they develop a strong root system. If the plants do not establish strong roots when they are quite young, they will not develop a strong root system later in the season once the focus of the plants shifts towards fruit production”. They do not promote the idea of removing flowers to help with this root growth.

Better Crops in Short Seasons

Growers with short seasons may be less interested in high yields and more interested in getting an early crop. Topping seedlings and removing early blooms will delay the early crop.

Creating higher yields of unripe fruit is also not desirable in short season growing areas.

Growing Hotter Peppers

What causes some peppers to be hot and how do you make them hooter? Find out in Growing Hot Peppers – What Makes Them Hotter?

Should You Prune Peppers?

There is no single right answer. Understand your goals and your growing season. Then decide which option is better for you.

There is probably little advantage in pinching pepper seedlings for home gardeners, but in long seasons it might produce a higher yield. Removing flowers has no benefit.