What you need to know:
Pruning is used to train the plant, maintain plant health, improve the quality of flowers, fruit, foliage, or stems, and sometimes even to restrict growth.
Understanding plant structure helps the home gardener select the limbs or flowers that require removal to improve the health or look of the plant. Resources such as the American Horticultural Society book Principles of Pruning and Training, or Sunset's Western Garden Book, are filled with specific plant life details. Knowing what a bud union is, or a tree crown, or a scaffold branch, or a crotch angle, and the difference between a tree and a shrub, is vital information when a homeowner is ready to begin the pruning process.
The next concern is timing—when to prune. Spring-flowering shrubs and trees that bloom on last season's growth, including azalea, lilac, rhododendron, redbud, Japanese quince, fringe tree, honeysuckle, and viburnum should be pruned soon after they bloom. This allows for vigorous summer growth and plenty of flower buds the following year.
Several years ago, my lilacs were getting tall and sprawly, so I took my loppers to them in the fall in an effort to ‘shape them up'. The following spring, I had tidy lilac shrubs, but very few lilac blooms. I had removed most of the lilac's growth from the previous spring and summer, not knowing lilac is one of the shrubs that bloom on the previous year's growth. Recently, our prolonged cold winter devastated my hydrangeas, resulting in the loss of all last summer's growth. I have very few hydrangea blooms now.
Abelia, butterfly bush, Hills of Snow (a hydrangea variety that does not bloom on the previous year's growth), hypericum, crape myrtle, and most shrub roses bloom after spring from buds which are formed on shoots that grow that same spring. Prune these shrubs in later winter to promote vigorous shoot growth in spring.
Broad-leaved evergreens, such as gardenia, camellia, pyracantha, holly, and photinia require very little pruning. Go several years without pruning, except to remove dead or weak stems, or to keep them neat. Prune broad-leaved evergreens grown for showy fruit such as pyracantha and holly during their dormant season when needed for shaping. If these plants become old and misshapen, cut back to 6 to 8 inches from the ground before spring growth begins. Be mindful of cutting back too early, however, as pruning stimulates new growth, especially vulnerable to frost damage.
Understand the reasons for pruning landscape shrubs and trees, arm yourself with structural and growth knowledge about your specific plant, and be willing to take a hands-on approach to the pruning process You can accomplish the task!
Home gardeners who want to learn more about landscape pruning will find abundant information in the books referenced earlier as well as from these University of California websites:
http://cesutter.ucdavis.edu/files/102457.pdf
http://ceventura.ucanr.edu/Environmental_Horticulture/Landscape/Pruning/
UC Master Gardeners of Napa County is recruiting for the Class of 2015! Applications are available at two information meetings:
Friday July 11, 12.30-2.00
Tuesday July 22, 6-7.30
At 1710 Soscol Ave., Suite 4, Napa, CA 94559.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners ( HYPERLINK "http://ucanr.org/ucmgnapa/" http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
Napa County Master Gardeners welcome the public to visit their demonstration garden at Connolly Ranch on Thursdays, from 10:00 a.m. until noon, except the last Thursday of the month. Connolly Ranch is at 3141 Browns Valley Road at Thompson Avenue in Napa. Enter on Thompson Avenue.
As a gardener, I consider soil as the foundation for all I do. Like a friendship or marriage, it must be respected and nurtured if you want it to thrive and continue to be there for you. What soil isn't is dirt.
I recently read an article in The New York Times by Dan Barber, the chef and co-owner of the two Blue Hill restaurants in New York. In the article, he wrote about how much he liked a locally grown emmer,a wheat variety also known as farro. He had been extolling the virtues of this grain, but it wasn't until he visited the farm that he realized what made the emmer so delicious.
The farmer managed the soil not by adding chemicals but by rotating crops and including cover crops in the rotation. Crop rotation improves soil health which, in turn, affects the flavor of the food grown in it.
Crop rotation is another subject Master Gardeners learn about in training, and we preach it in the public workshops we offer. I thought I knew something about this subject, but after reading Dan Barber's article, I realized I had only scratched the surface in understanding its impact on soil. The article was about farming and not gardening but the same principles apply.
The practice of crop rotation has been around for centuries, and it takes many forms. It entails planting vegetable crops of the same family in different locations each year. What you plant, and the order in which you plant,makes a difference.
The reason for rotating crops is straightforward enough. Plants related to each other tend to be prone to the same diseases and insect pests. In my pre-Master Gardener days, I thought I was practicing good crop rotation when I planted tomatoes one summer, followed by potatoes in winter and chilies the following summer. But the chili plants were yellowish-green and produced scraggly, rumpled fruit, so I knew I had a problem.
These plants are all in the Solanaceae, or nightshade, family, so my crop-rotation plan was a failure. To correct my mistake, I had to take these beds out of production for a year and solarize the soil. In a nutshell, this technique involves removing all plant matter, wetting the soil, covering it with a plastic tarp and letting it bake for six to eight weeks in summer. Afterward, I planted a cover crop of fava beans.
Cover crops (also called green manure) are an integral part of crop rotation. They build productive soil, help control pests and diseases, attract beneficial insects, prevent erosion and suppress weeds.
Cover crops include grasses such as barley, oat, wheat and cereal rye; legumes like vetches, bell beans, field peas, clovers, cowpeas; and mustards of various types. All are low maintenance and require little water. To get the maximum benefit, cut the cover crop at the base when it flowers or when the seed heads emerge on grains. You can either incorporate the vegetation into the soil or allow it to decompose on the soil surface.
If growing a cover crop is not your thing, then follow another practice that Master Gardeners recommend: add compost. And we're not talking about just a little. Spreading several inches of compost on vegetable beds before planting should dramatically improve your harvest.
The next time you harvest a tasty ‘Early Girl', ‘Black Krim' or ‘Hawaiian Pineapple' tomato, remember that the soil contributed more to flavor than the variety did. On the other hand, if the tomato is tasteless and mealy, don't blame it solely on the variety. Think about how you managed the soil during the growing season.
Workshop: Napa County Master Gardeners will conduct a workshop on “Pruning Landscape Trees and Shrubs” on Sunday, June 22, from 2 p.m. to 4 p.m., at the Yountville Community Center, 6516 Washington Street, Yountville. Proper pruning enhances the beauty of landscape trees and shrubs while improper pruning can reduce their landscape potential. Learn guidelines for proper pruning. This workshop may include a field trip to observe pruning in a local garden. To register, call the Parks & Recreation Department at 707-944-8712 or visit its web site.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.
Napa County Master Gardeners welcome the public to visit their demonstration garden at Connolly Ranch on Thursdays, from 10:00 a.m. until noon, except the last Thursday of the month. Connolly Ranch is at 3141 Browns Valley Road at Thompson Avenue in Napa. Enter on Thompson Avenue.
Calls to the Napa County Master Gardener help desk indicate that local gardeners need pruning advice. Many callers want to know when to prune, which is an excellent question. When shrubs fail to bloom, pruning at the wrong time is a likely cause.
Summer-and fall-flowering shrubs are generally pruned in winter when they are dormant. They flower on new wood that grows earlier in the same growing season. Pruning them back in late winter or early spring encourages more new growth and results in more flowers. Butterfly bush (Buddleia), honeysuckle (Lonicera fragrantissima) and rose of Sharon (Hibiscus syriacus) belong in this category. Many summer-flowering shrubs grow quickly and can take heavy pruning. I cut my Buddleias back every year to 10 to 12 inches, and they become six-foot giants again by the end of summer.
In contrast, spring-flowering shrubs bloom on old wood. That means they produce their flower buds on twigs that grew the previous summer. Although it is tempting to cut all shrubs back when doing your winter cleanup, resist that urge. Pruning spring-flowering shrubs in winter will eliminate most of their blooms.
In general, you should prune spring-flowering shrubs immediately after the flowers fade. Plants in this category include lilac (Syringa vulgaris), mock orange (Philadelphus) and viburnum (Viburnum spp.). Many spring-flowering plants do not need heavy pruning every year and are content with selective thinning to give them shape.
Hydrangeas present a pruning quandary. Some varieties bloom on old wood and others on new wood. Before taking pruning shears in hand, you need to identify the hydrangeas you have.
The large hydrangeas with blue or pink and sometimes white flowers (Hydrangea macrophylla) and oakleaf hydrangeas (Hydrangea quercifolia) both bloom on old wood. Prune them lightly right after flowering. The shrubs with white conical flowers (Hydrangea paniculata) and some of the other large-flowered hydrangeas (Hydrangea arborescens), such as the popular ‘Annabelle,’ bloom on new wood. Cut them back in late winter.
I have several Hydrangea macrophylla growing just outside my kitchen window. I once mistakenly cut them back severely in winter and the result was no blooms the following year. When I cut them back just after flowering, they bloom the following summer but the plants block much of the window before they finish blooming. So I am left with the dismal choice between glorious flowers and a view. This is the perfect example of wrong plant in the wrong place.
Regardless of when your shrubs bloom, you can prune them lightly anytime to remove damaged or diseased wood or to eliminate weak or unwanted growth. This clipping will safeguard the health of your shrub.
Improper pruning not only affects future blooms; it can also destroy the shape and health of the plant. Some gardeners have a tendency to create dense, round balls. Others top their plants or go for the lollipop look. It is best to respect the nature of the plant and prune judiciously.
One method is to cut branch by branch to shape the plant. Cut at branch unions or buds while avoiding shearing in a uniform hedge. Shearing is easier and faster but creates a shell of foliage, and the plants eventually become woody in the interior.
You can rejuvenate many types of shrubs by cutting them to the ground in early spring. However, you will sacrifice that year’s blooms on spring-blooming shrubs. Another method of rejuvenating an older shrub is to cut one third of the canes to the ground each year for three years until all canes have been rejuvenated. This practice works well on multi-stemmed twiggy shrubs.
We prune plants for many reasons: to control their size, maximize flowering, train them, improve their appearance and rejuvenate old, tired shrubs. Invest in a good pruning book, and prune each shrub according to its needs to avert a horticultural disaster.
Pruning is not always what a plant needs. Sometimes it’s wiser to just remove an overgrown plant and replace it with one more appropriate for the site. I intend to stop doing battle with the giant hydrangeas under my kitchen window and replace them with a more appropriate choice. Then I will have the luxury of both flowers and view.
Workshop: Napa County Master Gardeners will conduct a workshop on “Landscape Trees and Shade Gardens,” on Saturday, October 12, from 9:30 a.m. to 11:30 a.m., at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Wondering which trees do well in our valley and how to place them in your garden for years of shade and beauty? Learn which plants grow well under oaks and other trees, creating thriving shade gardens. Online registration (credit card only) Mail in registration (cash or check only). Sorry, no refunds unless workshop is cancelled.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.