Introduction
Topping plants is a common pruning technique used by gardeners to control plant height and promote bushier growth. It involves cutting back the main stem(s) of a plant to just above leaf nodes to encourage the development of multiple side shoots. Knowing when to stop topping outdoor plants is important to achieve the desired effects and avoid over-stressing the plant. In this comprehensive guide, we will discuss when and why to stop topping different types of outdoor plants.
When to Stop Topping Trees and Shrubs
Most trees and shrubs should only be topped when young. Mature trees and shrubs should not be repeatedly topped as this can permanently disfigure and weaken them.
Young Trees
- Stop topping deciduous trees once they reach the desired height, usually after 2-3 cycles of topping. More topping will sacrifice the tree’s natural form.
- Stop topping conifers like pines and spruces once the desired density is achieved, usually after 1-2 cycles of topping.
- Generally stop topping trees once they are 5-7 years old.
Young Shrubs
- Stop topping shrubs once they reach the desired size and fullness, usually after 1-2 cycles of topping.
- Stop topping shrubs at least 2-3 months before the first fall frost to allow new growth to harden off.
- Generally stop topping shrubs after 1-3 years of growth.
When to Stop Topping Flowering Plants
The timing of stopping the topping of flowering plants depends on the purpose and the type of plant.
To Control Height
- Stop topping perennials and annuals once the desired compact height is attained, usually mid to late summer.
- Stop topping flowering vines like morning glories when they reach the allotted trellis height.
To Delay Flowering
- Stop topping mums and asters 6-8 weeks before the expected first frost to allow buds to form.
- Stop topping spring bulbs when the buds emerge, otherwise flowering will be delayed.
To Promote Bushy Growth
- Stop topping flowering plants once the plant is full and bushy, usually after 2-4 cycles of topping.
- Avoid topping mature flowering plants as the growth may remain stunted.
When to Stop Topping Vegetables
Most vegetables thrive best when topped at the right stage of growth.
Bush Vegetables
- Stop topping tomatoes, peppers, and eggplants once 3-6 main flowering stems have formed.
- Stop topping squash and cucumbers when the plant begins to flower and vine.
Vining Vegetables
- Stop topping melons, pumpkins, peas, and beans when 6-10 nodes have formed on the main stems.
- Avoid topping mature vining vegetables.
Why Proper Topping is Important
- Promotes bushy compact growth and curbs tall lanky growth.
- Delays flowering and extends the flowering period.
- Maximizes plant health and vigor.
- Avoids overstressing and weakening the plant’s growth.
- Allows enough time for new growth to mature before frost.
- Maintains the natural form of trees and shrubs.
Things to Keep in Mind
- Do not top plants too late in the season.
- Avoid topping mature trees and shrubs.
- Top only 1/3 to 1/2 of new growth at one time.
- Use clean, sterilized tools to avoid transmitting disease.
- Prune just above an outward facing leaf node.
- Destroy all topped plant parts to prevent pest infestation.
- Provide plants extra care like water and fertilizer after topping.
Conclusion
Knowing when to stop topping plants is crucial to maintain their health and achieve your gardening goals. As a rule of thumb, stop topping outdoor plants once they attain their desired size, fullness, and purpose. Allow enough time for new growth to mature before the first fall frost. Avoid excessive topping that can stress plants and affect flowering and fruiting. With proper technique and timing, topping can be an extremely useful tool for shaping and managing all types of outdoor plants.