Dear Helen: Our squash planting is afflicted with powdery mildew. Applications of a baking soda mixture have not stopped the problem. My husband wants to empty the plot and I want to let the squash mature before disposing of the infected plants. Perhaps your advice will help to preserve marital harmony in our home.
K.M.
Dear K.M.: With sincere hopefulness that they will not cause any further rupture in marital harmony, here are some thoughts on your squash planting problem.
In most gardens, powdery mildew is almost inevitable on squash plants in late summer, when night temperatures become cooler and overnight dews raise humidity levels. I leave my winter squash (and pumpkin) plantings to die back, either with the season or the mildew, and allow the squash to mature. The disease does not affect the squashes. I keep zucchini and other summer squash plants going as long as they continue to produce fruits.
Oddly enough, though powdery mildew spores germinate quickly in humid conditions, they cannot germinate when there is water on the leaves. Rinsing the leaves with water several times a week, in the middle of the day, can help to curtail the disease.
A blend of one part milk to nine parts water sprayed weekly on sqush (and cucumber) leaves acts as an effective fungicide. Sulphur sprays control powdery mildew, but frequent applications can damage squash and cucumber leaves.
Serenade is a biofungicide that suppresses powdery mildew on squash, cucumber, melons and pumpkins as well as on phlox and roses. It contains a strain of Bacillus subtilis that attacks fungal cell walls and destroys the fungal cell.
All these controls are most effective when begun early in the season, or at the first sign of mildew.
Avoid letting the soil dry out. Drought stress sets plants up for an infestation of mildew. Take care, though, not to overwater. Soggy conditions facilitate the spread of this fungal disease.
Dear Helen: Please tell me the name of the vine in the attached photo.
P.S.
Dear P.S.: It is a Campsis, commonly called trumpet creeper for the shape of the flowers. Your variety is probably Campsis tagliabuana 'Madame Galen,' which bears loose clusters of salmon-red flowers. This is a popular hybrid between C. radicans (red-orange flowers) and Chinese trumpet creeper (C. grandiflora chinensis).
Trumpet creeper has compound leaves, each usually bearing nine to 11 leaflets. The bloom period is July through September. Madame Galen grows to about nine metres.
Campsis vines thrive and bloom best in warm, sunny sites with a moist, humus-rich soil.
Dear Helen: I have noticed the hardy geranium 'Rozanne' blooming in many gardens this summer. I love it and would like to add more varieties of this perennial to my garden.
Can you direct me to a good local source?
J.S.
Dear J.S.: Most local garden centres carry an assortment of hardy geraniums, with the best selection being in early to midspring.
You can get a good sense of the varieties available to local outlets by viewing them on the website of Heritage Perennials (perennials.com), a major wholesale supplier to nurseries. Type "Geranium" into the search box to access 81 listings, shown in sets of 12. Click on ones that appeal for a larger photo and detailed plant profile that includes preferred growing conditions and the plant's best uses.
The profile on Rozanne notes that it was selected as the 2008 Perennial Plant of the Year and that flowering starting in early summer can continue for weeks or even months if the weather is not too hot.
Rozanne is a British import, from Blooms of Bressingham.
You could compile a list of the plants you want and then look for a local garden centre willing to bring them in for you next spring.
GARDEN EVENT
Master gardener program. Because of an increased interest in the master gardener program, the Victoria Master Gardener Association will be running a fall class starting Sept. 6, at the Horticulture Centre of the Pacific, 505 Quayle Rd. in Saanich. This is an interesting, ambitious course for avid gardeners who wish to increase their knowledge. The course runs over a 16-week period and comprises 31 three-hour sessions that include classroom instruction, field trips, home study, assignments and in-class projects. For more information, telephone 250-479-6162 or go to hcp.ca/become-a-master-gardener.
