THE BEST TIME TO PRUNE PINE TREES

From the Torrey pine trees in La Jolla to the Jeffrey pines in Mount Laguna, pine trees are a common sight in San Diego County. These remarkable trees, with their unwavering beauty and tenacious resilience, grace residents with a glimpse of nature amidst the various neighborhoods in San Diego. However, as resilient as these trees are, the different species that call San Diego home do require careful consideration as to when to prune them.

Among San Diego’s pines, the Torrey pine is one of the city’s most beloved trees. There’s a good reason for it too — it’s the rarest native pine in the United States, and possibly the rarest in the world. San Diego also has the honor of being one of two places where it grows naturally. Alongside the Torrey pine, a mix of other species, such as the Norfolk, Aleppo, Ponderosa, Italian stone pine, Monterey, and Jeffrey pine, paint the city with wonderful greenery all year round.

Photo courtesy of Calscape.

Photo courtesy of Calscape.

While pine trees are very resilient trees, if you have one or more on your property, it is important to know the proper time to have them trimmed. Unfortunately, not all tree trimmers follow this basic “Pine Tree Trimming 101” knowledge, so it helps, as a consumer, to know when you should and should not contract a tree service company to prune your tree.

So when is the best time to trim your pine? Winter is ideal, but any time during the colder time of the year works too. Here in San Diego, we may not receive many super frigid days, but late fall through winter is the best time to schedule a pine tree pruning. Once the days start to warm up come spring, it would be too late, and you would need to wait until the weather cooled down again.

When the seasonal temperatures in San Diego drop, so do the physiological systems of pine trees as they prepare for dormancy. Yes, like grizzly bears, pine trees go to sleep in the winter. Just as with a surgical patient, the best time to perform surgery is with the patient asleep. When pine trees are trimmed during dormancy, it is ideal. If you cut away at a pine tree during the summer, it can not only put the tree into stress, but the pine also “bleeds out” sticky sap that is bad news for a variety of reasons:

• it is extremely messy.
• it can damage property below.
• it is a red flag for pests.
• it interferes with sealing pruning wounds.

Photo courtesy of Goldeagle.com.

Sap flow in a pine tree slows down as the weather temperature drops. In freezing conditions, it comes to a stop — simply because it freezes. Most of San Diego doesn’t experience below-freezing temperatures, however, when the winter cold hits, the flow of sap in pine trees slows down tremendously. While pine trees are not deciduous, they were similarly designed to conserve energy during the time of the year when sunlight is limited. And with the shorter days also comes the colder weather. Then when the temperatures rise in the spring, the sap flow speeds up again.

When limbs of a pine tree are trimmed off in the warmer months, their sap drips out like gooey honey dripping out of a bottle. As you can imagine, cleaning up this thick, sticky goo is difficult. Better yet, when the sap gets cooked in the sun and hardens up, not only is it harder to clean up, but it can also damage property. One of the most common victims is the innocent car resting below. Also, the roofs and exterior walls of homes, driveways, and curbs are a few other unfortunate casualties of the dreaded dripping sap.

Plant and tree pests are attracted to weaker and injured hosts. A healthy pine tree is more difficult to infest, but a sickly or dying tree is a much easier. Bark beetles also release pheromones to attract other beetles after they have successfully bored through the bark of a tree. It’s their “Come Join the Party” invite.

If a boring beetle penetrates into the bark of a pine, a healthy tree’s sap flow is typically strong enough to stop further penetration because it pushes the beetle out. Weaker trees do not possess the same vitality, so they tend to be easier to invade. However, beetles getting pushed out by sap is not necessarily always a win-win situation. The tree may have been able to defend itself against a few perpetrators, but it has now started “bleeding out” sap — a sign of injury. And like blood to a shark, the bleeding sap attracts these voracious boring pests.

All trees benefit from trimmings in one way or another, whether it is just for aesthetic appeal or for physiological purposes, such as encouraging root, foliage, or fruit growth. When dealing with urban pine trees in San Diego’s landscape, they can benefit for a number of reasons, as long as they are trimmed during the proper timeframe of November through March. This timing, of course, varies around the world, depending on the climate of a region.

When you contact LC Tree Service to assess your pine tree for a trimming, our arborists will be able to detect any limbs that could potentially pose a risk of falling. If it appears as if it would pose an immediate threat, then we would recommend having them pruned off immediately, regardless of the season. However, pine trees have a tendency to hold onto limbs very well, so often times, these branches can wait until the colder season to be trimmed off. Usually, these limbs tend to be smaller, so since they are lighter, they possess less of a downward pull.

The Torrey pine tree has a tendency to grow long, extended lateral branches, which are extremely heavy. If one of these limbs appears to be in a compromised state and likely to break, then an immediate trimming is usually recommended, even if it is in the middle of summer. Think of it this way. Would you rather deal with messy sap drippings or a fallen 2,000-lb branch on your roof?

Thinning the canopy of a pine also allows for improved air circulation. This is vital for reducing the chance of tree failure because when strong winds hit, it will have less push on a thinned-out tree, since the air is generally able to blow through it much easier than an untrimmed tree. While other factors also contribute to tree failure, trees with heavy, dense canopies have greater chance of being pushed over by the wind.

In San Diego, two of the most popular pine tree species that have a tendecy to grow dense canopies are the Canary island pine and Aleppo pine.

Besides safety, thinning the canopy of a pine tree possesses a few important health benefits. First, it allows for greater sunlight penetration, which allows for the inner foliage that is normally shaded to absorb more sunlight and boost their vitality. Next, trimming a tree enables better air circulation, which helps to reduce the risk or growth of fungal infections. Lastly, through regular prunings, unhealthy or compromised branches can be removed, and this helps with the tree’s overall condition.

Pine trees are such a diverse group of trees with different characteristics and shapes. Some grow into a predictable conical shape and need no help with their form. Such trees that grow in San Diego are the Ponderosa and Jeffrey pines, which are seen throughout our mountain communities, like Mount Laguna. Other pine trees can develop a more irregular or round shape that could benefit visually with regular pruning. Some of these pines that are common in San Diego are the Aleppo and Monterrey pines. Pine trees, such as the Canary Island, not only need help with their shape, but also with thinning their dense canopies.