Congratulations, you’ve made a commitment to adding container plants and shrubs to your deck or patio. If the pots are planted with perennials, they’ll need to be pruned from time to time in order keep them healthy and sized appropriately. In this article Sarah Marcheschi, staff gardener and feature writer, explains how to prune container plants.

Why growing container plants is a good idea

Whether looking to dress up the deck in your backyard, or to decorate a terrace, containers provide an opportunity to grow varieties of plants that may seem out of reach due to the constraints of light, soil, and space, or even weather. For the most part, growing shrubs in containers is not much different from growing them in the ground. However, they must be watered more frequently, and pruning involves a few extra steps (root pruning, anyone?).

Photo by Sarah Marcheschi

Why container plants need to be pruned

Though shrubs grown in containers sometimes require little in the way of pruning, it is a useful practice as a form of preventive maintenance. This encourages fruit or flower development, and addresses damage from insects or disease. Pruning is also frequently used to change the size and shape of the plant for aesthetic purposes. This can be by fashioning branches into a charming topiary, or preserving a desirable form. The health of your plants can be promoted by removing dead or dying branches, as well as branches that have sustained wind or storm damage.

When to prune container plants

Pruning is best undertaken in the late winter to very early spring, before new growth begins. That way, wounds on the plant are only exposed, (i.e. susceptible to diseases), for a very short time before new growth starts and wounds heal. It is easier to see the shape of the plant before leaves emerge and obscure the structure of the branches. The exceptions to this rule are plants that bloom early in the growing season on growth from the previous year. In this case, you may prefer to hold off on pruning until after they’ve finished blooming. Some notable examples include azaleas, rhododendrons, forsythia,lilacs,magnolias, and bigleaf hydrangeas (Hydrangea macrophylla).

Make sure pruning tools are in good condition

Before getting started, make sure you have the proper tools for the job, and that they are in good condition. Maintain hand saws and pruning / lopping shears by keeping them clean and sharp. This makes your job easier because it improves their performance and allows you to make clean cuts to branches. This not only look better, but heal better and are far less likely to invite disease. A pair of pruning shears is ideal for making cuts up ¾ inches in diameter. The long handles on a set of lopping shears makes it easier to wield when cutting thicker branches.