Should You Prune Evergreens in December?

Heading into winter, the garden becomes a quiet place of repose. Gardeners hang up their tools and get cozy indoors for the festive season. As deciduous trees and shrubs drop their leaves and slow their processes, evergreens become the focal point in winter landscapes. 

Since this is the period when those plants are most prominent, you may notice them more during this time. It’s natural to want to do a bit of shaping now that your evergreens are in full view. This begs the question, is it a good time to pull your pruning shears back out, or is there a better time to trim?

Some evergreens don’t require regular pruning, while others prefer a trim from time to time. If we pay attention to growing cycles, these plants grow at much the same time as their deciduous counterparts. So, should you prune evergreens around the winter holidays or look to other times of year for this undertaking?

The Long Answer

Evergreen trees and shrubs have relatively low maintenance needs. They tend to grow in an attractive, well-balanced form and do so independently of intervention. If you choose to prune these evergreens, there are good times and times that are less than optimal, in addition to times of year when it can be downright detrimental. 

When to Refrain

The most important period to refrain from using pruners on your evergreens is when they have finished growing for the season and winter is on the horizon. This falls from late summer until mid to late fall. In milder climates, where the weather stays warm longer, this time extends along with that warm weather.

Pruning during warm or mild weather causes a flush of new wood in most plants. Trimming the ends of branches encourages them to branch and put out new foliage. This new growth is tender and more susceptible to cold. Softwood is much less cold and hardy than wood, which hardens off over the summer. 

Since most evergreens grow the majority of their wood in the spring, they take the summer months to harden off. This mature wood lasts through the winter without dying back. If you prune too close to the temperature drop, the new wood produced may not survive the winter and could expose the tree to added stress. 

It’s best to avoid pruning entirely from late summer onward. The exception is for dead or diseased branches. You should remove damaged wood any time it shows up to avoid spreading the damage to other parts of the plant. 

When to Proceed With Caution

There are two periods of the year when pruning is unlikely to result in damage. Though these are not ideal, you won’t end up with a tree covered in dead branch tips that you’ll need to cut back harder after the winter. 

If you prune evergreens at the end of spring, you miss the ideal period, but it won’t do any damage. You may not see optimal spring growth, but your evergreen still has time to harden up any new wood before winter, and it should survive. 

In midsummer, when the weather is hottest, most evergreens enter a semi-dormancy, which helps them withstand the intense heat. You can prune during this time, but pay attention to the date. Once you get to late summer, this window closes, and you should hold off for the remainder of the year. 

This brings us to the month in question, December. December is an in-between month that most consider to be winter, but most of the month is still technically late fall. It’s only after the solstice that we enter into true winter. Depending on your climate, this can be an acceptable time to prune, but it’s still not ideal. 

In warm climates, like where I live in Zone 9, December is a funny month. It can be warm and balmy, but it can also bring on some cold temperatures. A few years ago, we had an unseasonably cold Christmas week and winter in general. In this case, it would be fine to prune, as the tree would remain dormant. 

However, if you have a warm December, pruning during this month can cause new wood to grow, followed quickly by the coldest months. This makes it risky as the plant can begin to produce new growth in a short time. Then, when that cold weather does show up, your tree is in for a difficult time. 

I would say that in December, you should hold off on pruning unless you live in a cold climate. If the tree or shrub remains dormant after trimming, it should be fine. If not, you run into the same issue as happens with fall pruning. 

When to Go Ahead

The ideal time to prune and shape up most evergreens is in late winter or very early spring. Right before the plant re-enters, its growth season is best. Since pruning encourages growth, trimming just before it begins a growth phase will maximize that new growth.

Pruning just before your evergreens begin to grow will leave you with optimal growth. It will create fullness and make your plant look lush and happy. Most of these plants put out only one flush of growth per year in the spring. By pruning just before that period, your plant gets the signal to grow, and it will do precisely that. 

Most of these shrubs and trees require only minimal shaping, as they grow in a nice form naturally. Let’s discuss the proper way to prune most evergreens in the spring. 

How to Do It

Different types of plants have different growth habits, and thus, they require a different approach to trimming. 

Pine, fir, spruce, and hemlock need the least amount of cutting as they naturally grow in an attractive, conical, or pyramidal shape. Avoid cutting their lower branches, as this ruins that pretty shape. Never cut the main leader, as this also destroys the shape of the tree. 

Clean up any dead or broken branches and those with the appearance of disease or pest damage. Cut away any crossing branches that interfere with airflow to the interior. These are those that cross through the center of the tree from one side to the other. 

You should also remove branches that cross over their neighbors and wear on others. Select the strongest limb and remove the others that cross over or beneath it. When removing an entire branch, make sure to cut it all the way to the trunk. Using a hand saw can help protect the bark around your cuts. 

Pine – Allow your pines to form candles. These are small branches that grow upward from the ends of branches. Typically, there is one candle that’s stronger and larger than the others. Trim or snap off all but that strongest candle at about one-third of its length. 

Spruce and Fir – These produce new growth once per year from terminal buds. Tip the branches back to one of these buds, cutting just to the outside of the bud. Don’t leave stubby growth at the ends of branches. This will produce unattractive branching. 

Juniper and False Cypress – These don’t need more pruning outside of cleaning them up. Trim off old, damaged, or broken limbs and any that cross over others or through the center. Cutting the ends off of branches on these will reduce the foliage and leave you looking into the center of the plant. 

Hemlock, Arborvitae, and Yew – These tolerate more pruning, and doing so will keep them more compact and bushy. They grow in spring and summer, so you can trim them any time from early spring to mid-summer. The branches will produce new growth at the ends, which cover over the trimmed ends.