Topping Plants: Boosting Crop Yield and Quality

If you’re new to growing — or looking for ways to improve your garden — you’ve come to the right place. What if I told you there was a way to increase the yield and quality of your crops with one simple trick? Well, there is. Let’s talk about ‘topping’ — what it is, when to do it, and how topping will help your crops produce more with very little effort.

What is Topping?

​Topping has been around for years, and many gardeners use the technique to get the most out of their crops. Think of topping as a high-stress training technique for your plant. It involves removing/cutting the plant’s main stem to promote more lateral growth — resulting in a bushier plant with more main branches (colas in cannabis). It opens the plant up for better light penetration, which typically leads to higher yields. Topping is commonly used in certain plant crops, including grapevines, tomatoes, and cucurbits (zucchini, pumpkin, squash, cucumber), and is common practice in cannabis cultivation.

​How does Topping Work?

How topping works is relatively straightforward. Naturally, a plant exhibits ‘apical dominance’ — where the center (main) stem has the most vigorous growth because it has the highest concentration of growth hormones called ‘auxins’ — which are at the tip of the plant. That tip is called the ‘apical meristem’. When the main tip is removed, that apical dominance no longer exists, and the plant’s energy and auxins are redistributed to the lower parts of the plant where lateral branches exist. As those branches take on more energy and hormones, they begin to grow outward and upward, resulting in more main stems on the plant.

Cannabis

​In cannabis, topping is very popular amongst growers — especially where space is limited. Topping helps manage plant height (very important for tiered growing or low ceilings) and increases the number of main cola sites, leading to higher yields and better quality throughout the crop when done properly. This is due to more main branches and better airflow throughout the plant as it develops — all very important factors when growing cannabis or other fruits.

Tomatoes

Numerous tomato varieties respond well to the technique. Topping can be done as the plant is growing in a vegetative state, but not during flowering until near the end. If done during early or mid-flowering, the plant will become stressed, and flowering development will be disrupted, resulting in lower yields and, more importantly, reduced quality. Topping can be done during late flowering in tomatoes and other vine crops. When this is done late in flowering or near harvest time, the plant no longer grows vertically and instead focuses its energy on ripening fruits before harvest or cold weather sets in.

Curcurbits

Cucurbits (zucchinis, cucumbers, squash, pumpkins), grapevines, and broad beans can all be topped to limit excessive vine growth. Topping also helps strengthen the plant’s lower structure, improves airflow, and increases sunlight penetration to developing fruit, which is super beneficial for preventing fungal diseases like powdery mildew.

Basil

Enjoy growing Basil? Removing the apical meristem prevents the plant from flowering and going to seed. This makes the plant produce more leaves and helps preserve the plant’s flavour. Who doesn’t love having perpetual basil on hand?

Top Tips

​In most cases, topping should occur during the vegetative phase while the plant is still developing. Don’t do it too early either, or you won’t have enough lateral branches developed to make a significant difference.

​Use clean tools. I can’t stress this enough. Always ensure your scissors or blades are sanitized and cleaned before use, and after topping is completed, to prevent viroids, pathogens, or bacteria from being passed from plant to plant in your garden.

​Recovery time is very important for plants that have been topped. Allow your plant at least several days, up to a week, before performing any other defoliation and/or topping. The plant needs time to recover from the stress it’s been put under. Once recovered, it will grow more vigorously from the bottom and mid-section.

​Topping helps increase the number of flower/fruit sites. By diverting the hormones from one main stem to many, not only will your yield increase, but the quality of what you’re growing will improve as well.