A friend recently planted some citrus trees and asked me for tips on pruning. That sounds like a simple request, but when you look into the subject you find all manner of complications.
First, there are 12 categories of citrus — Sweet Oranges, Sour Oranges, Lemons, Mandarins, etc. — and they differ in pruning requirements. Second, citrus are grown on various rootstocks, which affect growth habits and, therefore, pruning practices.
Further, citrus farmers have developed various pruning systems to maximize yields and labor efficiency. As R. Sanford Martin says in “How to Prune Fruit Trees”, writing about a lemon tree pruning system: “The tree may not be the most symmetrical in shape, but it will be producing an abundance of high quality lemons.”
He goes on to say, on the other hand, dwarf bush lemons require practically no pruning.
I can attest to that, having a bush-form Meyer lemon in my vegetable garden area. It is about 24 years old, symmetrical, healthy and green as can be. It produces a year-round supply of high-quality lemons, and it gets very little pruning.
To keep it simple, let’s just consider general pruning for freestanding dwarf citrus in the home garden — not espaliers, hedgerows, or commercial production.
Pruning objectives for ornamental citrus include:
1. Remove dead, dying, and broken branches.
2. Remove rootstock suckers growing from below the graft.
3. Prevent or correct crossing, rubbing branch structure.
4. Maintain low foliage and fruit elevation about 2 feet above ground.
5. Remove crowded branches to allow scattered sunlight into the inner canopy.
6. Maintain a desired size and shape.
Because most citrus are thorny, put on pair of leather gloves and a denim or leather jacket to protect you hands and arms before grabbing any pruning tools. And remember safety glasses for eye protection. These are an ANSI requirement for commercial tree workers.
Next, because citrus woody stems are tough, supplant your hand pruners with a small, sharp, pruning saw. If you cannot easily make a cut with your hand pruners you are likely to leave an ugly wound on the tree.
Getting started with a new tree, it is best to prune only to remove dead, dying and broken branches at planting time and then let the tree grow for at least a year.
The pruning objectives should be attended to in the second year and beyond as a long-term, low-intensity process. Consistent light pruning prevents the need for hard pruning with large diameter pruning cuts.
With respect to timing, most citrus pruning can be done any time of year, but avoid heavy pruning in late summer. Heavy pruning induces a sprout response, and the sprouts are frost tender unless they have plenty of time to mature and harden. So, for an overgrown citrus that needs to be reduced in size, do it in late spring or early summer.
Considering fruit production, citrus produces flowers mostly on one-year-old stems, not the current season’s new growth, so be sure your pruning conserves plenty of new shoots for fruit production next year.
Sudden Oak Death workshop
A free workshop on the prevention and management of Sudden Oak Death (SOD) will be presented in Napa by the University of California Forest Pathology and Mycology Laboratory on Oct. 28, 10:30 a.m. at the Napa County Public Library, 580 Coombs St.
Volunteers in Napa have participated with the UC Lab in the SOD Blitz effort seven years in a row.
In previous years, the SOD Blitz has pinpointed the disease at many locations in Napa County.
Dr. Matteo Garbelotto, director of the UC Berkeley Lab, will discuss the results of this years SOD Blitz and provide practical information including:
— How to assess the risk of your trees becoming infected.
— How to recognize the symptoms in oaks and in plants that carry the disease.
— How and when to apply the material that has proven to be effective in preventing infection, both by the trunk spray method and the trunk injection method.
— Managing California bay laurel trees, the most significant carriers of the disease.
I will be there to introduce Dr. Garbelotto and answer questions on the Napa Blitz effort.
The session is free and open to the public. Pre-registration is not required.