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Helen Chesnut's Garden Notes: Attractive tamarisk shrub an invasive species

Dear Helen: Can you identify the shrub or tree in the attached photo? I saw it blooming late last month at the end of the Oak Bay marina. The pink colouring is unusual. I can't find it it any of my plant books. L.M.

Dear Helen: Can you identify the shrub or tree in the attached photo? I saw it blooming late last month at the end of the Oak Bay marina. The pink colouring is unusual. I can't find it it any of my plant books.

L.M.

The plant is a tamarisk, a shrub or shrubby tree with small, blue-grey leaves on feathery, arching branches that are covered in late summer with big, feathery sprays of pink blossoms.

I don’t know the species or named variety of the plant you saw, but even the form named ‘Pink Cascade’ (Tamarix ramosissima ‘Pink Cascade’) is considered by the Coastal Invasive Species Committee (coastalisc.com) to be an “aggressive ornamental that should be prevented from escaping cultivation.”

The website of the Invasive Species Council of B.C. (bcinvasives.ca) is also useful. Tamarisk, with a full description and photos, is profiled on its list of invasive plants.

The Invasive Species Council also has a Grow Me Instead booklet that can be viewed online and printed out if desired. The booklet recommends smoke bush and Preston lilac, among other shrubs, as alternatives to tamarisk for gardens.

Dear Helen: I’ve heard that legumes such as beans can “create” their own nitrogen source. I’ve never understood how this happens. Can you explain?

S.P.

They don’t do it alone. The process, known as “biological nitrogen fixation,” is a mutually beneficial partnership between legumes (peas, beans, peanuts, clover) and a common soil bacteria (Rhizobium) that is able to convert atmospheric nitrogen into a form that the plants can easily absorb.

The process begins with the soil bacteria invading the plant and forming small nodules on the roots. The plant provides shelter and nourishment for the bacteria. In return, the bacteria in the nodules make usable nitrogen available to the plants.

Not all the legumes we grow are equally successful at fixing nitrogen.

Common beans are considered poor fixers. The roots on a bush bean plant that I pulled up recently had small, whitish nodules.

I’ve seen larger, pinkish nodules on the roots of fava (broad) beans, which are better fixers of nitrogen.

Dear Helen: My once beautiful Clematis armandii that I’ve had in a large pot for 15 years has produced, in the past few years, almost no flowers and the leaves are dry along the edges. What should I do?

E.H.

C. armandii is an evergreen clematis that produces pure white (‘Snowdrift’) or pink-blushed (‘Apple Blossom’) scented flowers in March and April. These are vigorous vines not really suited for container cultivation. And 15 years is a long time for a vine in the same container.

One option is to purchase a new, young C. armandii, preferably in early spring, and plant it in a sheltered site in the garden.

This clematis is easily damaged by a hard frost. Or, replace the C. armandii with a clematis better suited to growing in a large container. Labels on nursery plants usually indicate this.

For blooms through the summer, look among the easily grown, summer-flowering C. viticella varieties. Many among them are good for containers.

They don’t have big, splashy flowers but rather an abundance of small blooms over a long season.

Dry leaf edges can have a number of causes. On your clematis it could be winter damage.

Sometimes this condition is simply a reflection of the season, but the most common cause is probably inadequate moisture in the soil.

Garden events

Dahlia show. The Victoria Dahlia Society will host its Annual Show on Saturday, Aug. 18, 1 to 5 p.m. and Sunday, Aug. 19, 11 a.m. to 5 p.m. in Prospect Lake Community Hall, 5358 Sparton Rd. There will be hundreds of dahlia blooms on display, and fresh cut dahlias for sale. Admission is free.

Organic plant sale. The Compost Education Centre, 1216 North Park St., will host its annual August Organic Plant Sale on Saturday, Aug. 18, 10 a.m. to 1 p.m. Local farmers will be selling organically grown winter vegetable transplants including kale, broccoli, cabbage, lettuce, chard and more. compost.bc.ca.

Government House nursery. The plant nursery at Government House, 1401 Rockland Ave. in Victoria, is open for public sales from 9 a.m. to 12 p.m. on Tuesdays and Thursdays through to Aug. 30. The nursery is located opposite the Tea Room. Plants for sale include perennials and grasses at great prices.