Tricks for growing great wisteria

Grace C. of Santa Rosa asks: I have two wisteria plants growing up a big, sturdy arbor. It has grown quite a lot in one year. How do I prune it so it will produce flowers every year, and to control its size?

To have your wisteria looking its best during the growing season, plan on pruning at least once in summer, and again in winter.

Summer pruning: Prune the long shoots back after the flowers fade. Since wisteria flowers develop on the previous year’s growth, pruning them biannually will not only keep these vigorous vines to a manageable size, but will help to develop short branches close to the structure, full of blooms. You will need to prune the long shoots of the current year’s growth back to 6 inches in early summer after the vines have finished flowering. Prune off any shoots that won’t be a part of the main framework of the plant. Also prune off root suckers, especially on the grafted varieties. You can prune back any long shoots that grow more frequently than just one time in the summer. It just depends on how much time you want to spend pruning and how neat you want your vine to look.

Winter pruning: Prune back long shoots that have grown during the summer back to three to five buds in late winter. Also, prune back any of last season’s unwanted long shoots, which will be easier to recognize now because the leaves will be gone.

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Sally R. of Windsor asks: Why doesn’t my purple flowering wisteria bloom? They have been in the ground for 2 years now. I feel like I should pull them out and plant something else.

Wisterias are notorious for not blooming for one reason or another. Before you do anything drastic, ask yourself if the following basic cultural requirements for the plant are met:

Exposure: Late winter frosts and high winds may damage flower buds, especially those of Wisteria sinensis (Chinese wisteria). Conversely, wisterias bloom best after a year with hot summer temperatures.

Fertilizer: Are you fertilizing them with a high-nitrogen fertilizer? Wisteria fixes nitrogen in the soil, so too much nitrogen can cause excessive foliage growth with poor flowering.

Light requirements: Wisterias need at least six hours of sunlight per day, preferably all day long.

Seed-grown plants: The most common reason for wisteria not flowering is if you purchased a seed-grown plant over a grafted plant.

Grafted plants will typically bloom within two to three years, while seed-grown vines may take about five to seven years before flowering. Ask your local nurseryperson for help in selecting the right one.

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Sally F. of Healdsburg asks: I want to plant a row of roses along my driveway, but don’t have time to prune them back and maintain them. Are there any types of roses that don’t require a lot of care?

Well, check out the Knock Out series roses. They are practically perfect roses. The blooms of these shrub roses keep producing from midspring until well into fall. These shrub roses grow 2 feet to 4 feet high and wide.

In our warm climate, they can sometimes bloom well into December, which gives the garden nearly nine months of color for the year. Knock Out roses don’t require pruning to rebloom, and they are disease and pest resistant. There are several colors to choose from. You’ll be pleased with these.

Dana Lozano and Gwen Kilchherr are garden consultants. Send your gardening questions to The Garden Doctors, at pdgardendoctor@gmail.com. The Garden Doctors can answer questions only through their column, which appears twice a month in the newspaper and online at pressdemocrat.com.