Winter Pruning
Late winter pruning is an important part of landscape maintenance. It’s the best time to prune many evergreen trees/shrubs and trees/shrubs that bloom in late summer. Late winter is also a good time to do heavier renovation pruning on overgrown shrubs that can tolerate it; they will have the entire spring and summer growing season to rejuvenate.
Late winter pruning takes advantage of the fact that these plants are dormant, resting for spring’s regrowth.
You should not heavily prune spring-blooming plants (azalea, big-leaf hydrangea, forsythia, lilac etc.) in late winter, not because you will hurt them, but because you will remove flower buds. Light pruning to remove oddly shaped, broken or dead branches is fine.
The Basics
For basic pruning, remove any dead, crossing or rubbing branches (remove the worst-placed or weakest of the crossing branches), and suckers that have grown from the trunk or base of tree-form plants. Now step back and look at your plant. Do any branches catch your eye that are growing the “wrong way”, or that stick out and ruin the shape of the plant? Off they go too.
Make your cuts all the way back to the trunk or branch rather than in the middle of a branch. Where the smaller branch meets the main branch there is usually a slight ridge called the branch collar. Cut up to, but not into this area. (see illustration)
To maintain size without shearing, remove tips back to where they meet a branch. This method takes longer than shearing but results in a healthier plant. It also avoids damaging leaves which can affect the appearance of the plant as the cut edges brown.
What if your shrubs are terribly overgrown? For some shrubs, replacement is a sensible idea since they do not respond well to hard pruning, and begin to suffer more disease and die-out as they age. But some shrubs can be "renovation" pruned, which basically means lopping everything off to a few inches to a few feet. Renovation is drastic, but can have really great results on the right plants.
Renovation is easy. It just takes sturdy pruners, loppers and saws (plus a little courage the first time). Sprouting is quite rapid in spring. Here's what renovation looks like (click for larger pictures)
Before renovation. Shrubs are beginning to lose definition and grow into the walkway and over the windows.
Immediately after renovation pruning. Pruning was done in February.
Six months after renovation. Picture taken in August. Plants are Carissa holly (along walkway), Ligustrum (foundation) and barberry (under crape myrtles).
Pruning Common Landscape Shrubs
Here's how to approach pruning for several common landscape shrubs. Varieties that can tolerate renovation are noted.
Katie Cardille demonstrates pruning English Boxwood. (audio is low!)
Boxwood Although boxwood are commonly sheared, it is not healthy for them in the long run. To prune, remove stems back to a joining branch, opening up areas for light and air to penetrate. See video for details.
Buddleia (butterfly bush) For large types, cut main stem back to 18-36” (depending on how large you want it to be in summer) and cut back side branches to 2-3 buds. Thin branches may be removed completely. Can be renovated.
Camellia sasanqua Shorten any odd branches that are out of balance to a strong connecting branch. Apart from occasional thinning little other pruning is needed. Can be renovated with hard pruning if necessary.
Crape myrtle Believe it or not, crape myrtles do not require heavy pruning, and certainly not the regular decapitation that is commonly seen. Basic crape myrtle pruning is just a few steps: first remove all suckers from the base and trunk. Remove any branches that grow inward rather than outward. Optionally, prune thinnest branches back to the point they are about the thickness of your pinkie finger.
Daphne Daphne are so susceptible to disease that pruning is not advised except to remove dead or damaged branches.
Hydrangea paniculata & H. arborescens (‘Pee-Gee’ and ‘Annabelle’ types) Pruning is not required, but plants will develop fewer, larger flower clusters if pruned. Prune to a framework that’s between 12” to 24”, cutting stems back to the pair of buds closest to the framework. For tree-form varieties, this framework is on top of the trunk.
Ilex Cornuta (Burford, Nellie R. Stevens, Carissa) Similar to boxwood, remove dense areas to supply light and airflow. These hollies respond very well to hard pruning for renovation. Shearing tears leaves and is unsightly.
Junipers Junipers can be pruned by removing unwanted branches. They can also be pruned lightly to shape as long as you don’t cut into woody stems-once the growth has changed from soft and green to woody and brown it rarely sprouts back well, if at all. For this reason, it's important to select the correct size when planting, and then regularly shape junipers-if they overgrow replacement is the only option.
Knock Out & Groundcover roses It’s almost impossible to go wrong pruning them-you can practically do it blindfolded to any height. To prune with a bit more precision, cut back to 12” to 24” for Knock Outs , 8" to 18" for groundcover roses, and remove any branches thinner than a pencil. If needed, remove up to 1/3 of the interior stems to allow better air circulation to avoid disease. Once buds begin to swell as weather warms, clean up pruning by cutting back any damaged stems to fat, healthy buds.
Ligustrum Remove any shoots that have reverted back to green from variegation or back to common leaf shape. Otherwise, like boxwood, prune only to shape and to open up center to air and light. Overgrown Ligustrum can be renovation pruned.
Simple instruction on pruning Nandina domestica. (audio is high!)
Nandina Nandina is a cane-forming shrub. When pruning, remove old or ugly stems to the ground. This should encourage new canes to sprout from the base. Nandina should not be sheared. See video for details.