Campbell Vaughn: When is the right time to prune plants? It depends

One of the more consistent questions I get year around is “Can I prune this plant now?”

 

In other words, I don’t really like the way it is looking; or I know this plant needs pruning sometime; so I am considering getting out in the yard and making something happen. Well, I am here to help. There are some easy steps to follow.

A good rule to follow is to prune after a plant blooms. The reasoning is fairly simple. Once a plant blooms, it will rest a little while and then start forming buds for the following year’s bloom. The perfect example is the ubiquitous Augusta azalea.

These Asian natives bloom around Master’s Tournament time and then set buds for the next spring’s bloom in July. That gives us a good three-month window to get whacking.

Another good rule to follow is to not prune non-flowering evergreens like boxwoods, cleyera, ligustrum, pittosporum and podocarpus heavily in the fall and early winter.

Most plant’s response to pruning is to flush new tender leaves if the climate is right. Our weather can be warm when it isn’t supposed to be and that can mean new tender growth can sprout just in time for a hard cold spell. The tender leaves don’t usually handle the cold well and the new plant growth can get freeze burn. My recommendation is to wait until January to early March to trim back these evergreens. March is a good time to heavily prune hollies because they usually berry in the fall and winter.

A specific plant that I get asked about pruning this time of year are hydrangeas. Mophead hydrangeas (Hydrangea macrophylla) can be repeat bloomers. These shrubs bloom on both the old wood from the previous year and on the current season’s wood. The best time to trim them is in August. If you are a little late and wait until October you may be OK. By winter, you are too late. The ever popular ‘Lime Light’ hydrangea (Hydrangea paniculata) blooms later in the summer on this year’s growth, so pruning in the spring is just fine.

Oakleaf hydrangeas really aren’t meant to be pruned, but if you have to trim them, lightly cut them after they bloom in early summer. If you feel uncertain about which variety you have, a safe rule for all types of hydrangeas is that no pruning is better than the wrong type of pruning, so just deadhead the spent flowers.

A few other popular ornamentals that may need attention in the landscape are leggy plants like forsythia and nandina.

Forsythia doesn’t have a base stem, but grows as a bunch of individual canes.

Trim one third of the cane back at the soil line yearly. It is best to take the older canes out over the younger ones. Old fashioned nandina can spread over an area in time and become tall and leggy. This plant doesn’t grow from a single base so the best way to get fuller nandina is to stair step the cuts. Cut one at 12”, one at 18” and one at 24” until you have a desired massing. It’s best to wait to prune nandina until after they berry through the winter and spring.

These pruning tips are general recommendations and not rules. If you have a specific question about pruning a plant, let us know and I will be glad to help.

Reach Campbell Vaughn, UGA Agriculture and Natural Resource agent for Richmond County, by emailing augusta@uga.edu.

 

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