Pruning

The bare branches of January make this an excellent time for pruning. 

Winter pruning helps improve the appearance and health of trees, shrubs, and roses. The only exception is apricot and cherry trees, which are susceptible to Eutypa dieback. Apricot and cherry trees are best pruned in the dry months of summer.

Pruning goals

Different plants have different pruning needs, but the overall goals are the same: a balanced structure, adequate airflow, and the retention of productive limbs. There are two types of pruning cuts: thinning and heading. Heading cuts control height, while thinning improves air flow and sun exposure. Keep in mind, while pruning, that new growth will head in the direction of the remaining buds.

The first goal of pruning is to remove dead, diseased or crossing branches. Dead and diseased limbs can allow pests and disease easy access into healthy tissue. Crossed branches will rub against each other, causing similar problems. You will also want to trim away branches that are angled too closely together and those that hang downward.

Proper pruning protects people and property

Structural pruning reduces the likelihood of uprooted trees falling on you or your house. Trees with too much weight to one side also risk splitting the trunk and killing the tree. Pruning early in the tree’s life can create a safer, more balanced structure. While the depth and spread of tree roots depends on a number of factors (soil structure, irrigation, variety and age of the tree, and more), pruning can help the root system keep your tree upright. To give you an idea of how much weight we are talking about: an average mature hardwood tree, with a circumference of 100” inches at chest height, weighs nearly 13,000 pounds! Your average commuter car weighs 2,800 pounds - so imagine 4 or 5 cars hitting your roof in a storm to see why good pruning is so important.

How to prune larger branches

Pruning larger branches (those with a diameter of 2" or more), it is important to use multiple cuts to avoid peeling the bark beyond the final cut and damaging the remaining branch.

​In drought-prone areas with heavy clay soil, moisture retention is an art that most plants have mastered. This also means fungal diseases can be a real problem. Roses and fruit trees are especially vulnerable to brown spot, rust and fireblight. Pruning for good airflow between twigs and branches can help reduce these diseases. It can also provide sunlight to inner leaves, which translates into more vigorous growth and heavier fruit and flower production

Too much pruning is bad

​Now, as I’ve said before, too much of a good thing can be a bad thing. Excessive pruning can expose interior branches to sunburn. Also, while pruning some or a little can promote new growth, heavy pruning can cause irreparable harm or death to the plant. Before you start pruning, research the specific variety of plant to learn about its natural growth and shape. For example, some trees produce fruit on last year’s growth, while others produce fruit on new growth. There's no sense in cutting off your nose to spite next summer's harvest!

Fruit trees

The backyard orchardist will generally want trees that are small enough to make harvesting fruit easier, so you will want to use heading cuts to reduce the height of your trees.  Branches that grow vertically tend to be more vegetative, while horizontal branches produce more fruit. Branches growing at 45 to 60-degree angles tend to do both.

When you cut off the end of a vertical branch, phytohormones, such as auxins, will cause the remaining buds will send out new growth horizontally. When you tip a horizontal branch, it will send out new fruiting wood. This is also a way to prevent too much fruit developing and risking a broken branch.

It is always a good idea to remove suckers and water sprouts. Water sprouts are flimsy twigs that quickly grow vertically, directly from the trunk or older branches. Suckers are similar growths that occur at the base of the trunk or from the root system. These growths drain energy from the plant without providing any benefits.

Roses

In Mediterranean climates, roses never go completely dormant, but winter is still the best time to prune for better spring and summer blooms. Generally speaking, you will want to remove 1/2 to 2/3 of the existing bush. Remove dead, diseased and crossing branches and then reshape the bush for better airflow. You can learn more about pruning roses at the San Jose Heritage Rose Garden.

When pruning, it is best to cut close to the branch collar without cutting into it. You also want to avoid leaving nubs that interfere with a plant’s ability to heal itself. There is generally no need to apply sealants to pruning cuts. Plants have evolved an effective system for that all on their own.

Finally, be sure to keep your tools sharp and to clean your cutting tools between cuts. Use a household cleaner, such as Lysol. Otherwise, you may be spreading disease to healthy plant tissue.
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It can be incredibly rewarding to take before and after photographs of your pruning work. Feel free to share them with us!