Category Archives: winter pruning

Wisteria – Growing Tips & Maintenance

A pink Chinese wisteria covering a pergola in Bonny Doon

Wisteria season is winding down unless you have a repeat bloomer like a ‘ Cooke”s Purple’ or ‘Amethyst Falls’. I’ve heard it all: “Why doesn’t my wisteria bloom?” or “I planted a wisteria in the wrong place, how do I get rid of it?’ or “I love my wisteria but it’s taking over the porch ?” (insert garage, house, shed or other structure) Seems we either love ‘em or hate ‘em on our own property. Growing somewhere else they are always the stars of the spring garden. If any of this sounds familiar to you here are some tips on how to handle yours.

Wisteria are one of nature’s most resilient survivors. They are able to withstand and recover quickly from difficult conditions. To some they are a little too tough for their own good with a growth rate rivaling bamboo during the summer. If you dream of a wisteria-covered pergola shading your patio here are some maintenance tips that are sure to keep both gardener and vine happy.

A pink wisteria growing under a fragrant purple variety covers a gazebo.

Wisteria are so vigorous they can be pruned at any time, keeping them in bounds and clearing out unwanted or dead growth. Prune out any stems you see extending into eaves, windows or shingles. If yours has gotten away from you, you can even prune it down to the ground and start over with training although you’ll have to wait a few years for your vine to bloom again.

To their control size major pruning is done during the dormant season. Start by trimming the long tendrils that grew over the summer back to about 6 inches from the main trunk. Cutting the tendrils back in this way will initiate flower bud development, neaten the plant up, and show off the attractive trusty, gnarly character of the vines.

Whatever time you do renovation pruning remember the response of the wisteria to aggressive pruning is to literally explode with new runners. They put energy into new vegetative growth at the expense of flowering. Make sure you keep up on ongoing maintenance pruning by removing all unwanted runners right to their point of origin. Then prune back the others to 3 buds or sets of leaves. Repeated pruning of these runners is what will eventually give you spurs of wood, short laterals that in turn will provide you with flower clusters. You need to prune these runners all season long which ends up being every 3-4 weeks.

Do not fertilize your wisteria. They do not flower well if there is an over abundance of luxuriant growth. Over feeding also ends up giving them the means to become unmanageable monster. If you have trouble getting your vine to flower an application of a high phosphorus fertilizer may promote blooming.

A diligently pruned wisteria at Filoli Garden

Maintaining a wisteria requires some diligence but the reward is worth the effort. Remember this especially during winter pruning season to make summer maintenance easier. If you find that the wisteria vine has invaded a nearby bed, cut roots with a shovel below the soil line to control any that have wandered.

Which variety of wisteria should you get to cover your arbor, pergola, tree or other structure?

A Cooke’s Purple wisteria growing on a pergola in Boulder Creek.

Chinese varieties such at ‘Cooke’s Special’ have clusters of fragrant blue-purple flowers 20 inches long. This variety can re-bloom which makes it a favorite. Chinese wisteria can take up to 20 years to mature enough to produce flowers, but once it has matured, the plant is very long lived and can live up to 100 years.

Japanese wisteria like ‘Caroline’ bloom early with mauve flowers. ‘Royal Purple’. known also as ‘Black Dragon’ , has sweetly scented dark purple flowers. Japanese wisteria are most effective when grown on pergolas so their long flower cluster can hang freely.

American wisteria, native to more eastern areas of the U.S. is a smaller, less invasive species that grows ar about a third the rate of Asian wisteria. ‘Amethyst Falls’ blooms at an early age with lightly fragrant purple racemes. Use in containers for porch or patio, train up an arbor or trellis or as a small free-standing tree.

Silky varieties produce a profusion of short, 6 inch, fat clusters of strongly scented flowers that open all at once. They have velvety seed pods and bloom best in full sun.

All parts of the wisteria vine contain a toxin known as wisterin which can cause stomach upset. Growers should also be wary of pets and children eating the flowers or seed pods.

Pruning Plants in February

My plants are confused. Actually they know exactly what they are doing it’s me that’s confused. The mild winter, so far at least, has encouraged many of my plants normally still dormant at this time of year to start growing for the season. What’s a gardener to do when the roses, fuchsias, oakleaf hydrangeas and many other plants never really went dormant this year? Here are some February tasks that I’m going to be doing.

Cut back woody shrubs to stimulate lush new growth. Trim plants like Mexican bush sage and artemisia to within a few inches of the ground. Don’t use this approach on lavender or ceanothus, though. Lightly prune those after blooming later in the season and don’t cut back to bare wood inside the plant.

Prune fuchsias back by a third and remove dead, crossing branches and interior twiggy growth. Container fuchsias can be cut back to the pot rim. Do this right away if you haven’t already done so. A plant is wasting energy on new growth just to have it trimmed off later.

Cut back hydrangeas stems that bloomed last year and apply a soil acidifier if you want the flowers blue. Although aluminum sulfate is the traditional favorite for quickly acidifying soil it’s not as kind to beneficial soil microorganisms. Coffee grounds, pine needles, peat moss and cottonseed meal are better for your soil.

Miss Kim lilac

Don’t prune spring flowering shrubs like lilac, weigela and spirea or flowering trees such as cherry, plum and crabapple now. These and evergreens like rhododendrons, azaleas and camellias should be pruned after they flower. You can cut some branches while they are blooming to bring into the house for bouquets.

Even if you have pruned your roses be sure to remove old leaves still clinging to the plant even if the leaves look okay now. They will most likely develop fungal spots and diseases later if you don’t. Rake up any debris beneath the plant and discard to eliminate overwintering fungus spores

Roses are super forgiving and you can trim them up again using the following guidelines. The goal is to produce lots of roses not just a few of exhibition size. Aim for a vase-shaped bush with an open center.

Prune old garden roses that bloom once in the spring after flowering. Climbing roses require little pruning. Cut out extra stems if there are too many and also cut back long established canes to about the place where they are slightly thicker than a pencil. Then cut each side stem down to several inches. This will cause the cane to flower along its complete length for a beautiful spring display.

Wait to prune back perennials that may have their new foliage damaged in a late frost. Same goes for shrubs that might have gotten hit by frost. That damaged foliage can protect the plant from further frost damage. Mid-March is the estimated date of hard frost in our area or at least it used to be. We gardeners are always betting Mother Nature will go our way and our efforts will not have gone in vain.

Prune fruit, nut, shade trees and deciduous vines like clematis.

Cut back ornamental grasses if you live where you rarely get frost. I’m pruning California fuchsia, salvia ‘Bee’s Bliss’ and hummingbird sage now. They look okay now but I want the encourage new, compact growth.