Remove the spent blooms of these dahlias to keep them strong longer | The Compleat Home Gardener
Also tips and tricks for zinnias and begonias.
The beautiful flowers of late summer appear this month in the form of dahlias, zinnias, sedums (autumn joy) and rudbeckias in the August garden.
To keep your garden in full bloom, remove spent flowers, especially from verbena and fuchsias growing in hanging baskets. Harvest dahlias and sweet peas daily to maximize the number of reblooms, and prune petunias, lobelias, and other annuals that grow leggy.
If you don’t kid yourself and ruthlessly cut the plants in baskets or containers back by half this week and then fertilize and water them, you will be rewarded with plants that grow back and thrive more vigorously for two more months.
Q There is something wrong with my dahlia plant that I grew from a tuber. The leaves are speckled yellow and the plant is growing slowly. Do you think this is a disease? I don’t see any insects, but I have thrown slugs as bait on the plant when it was young. DG, Bonney Lake
A. My condolences. This sounds like a classic case of mosaic, a viral disease transmitted by aphids. There is no cure. The best thing to do is to remove the plant and tuber. Do not compost infected plant material. Be sure to plant clean, virus-free dahlia tubers to keep mosaic disease out of your dahlia bed.
Q I have had a lot of fun growing zinnias this summer. I have noticed some white dust on the leaves and hope it is not mildew. What should I do? T., E-Mail
A. Don’t panic, zinnias can survive an incipient bout of powdery mildew if you keep the leaves dry and the roots moist. Once you let a zinnia dry out, the mildew spores can penetrate the protective layer of the foliage. The secret weapon against powdery mildew is foliage that stays dry. You can place a protective screen over the plants when a rainstorm is expected and avoid watering with a sprinkler from above. Zinnias love a sunny location with rich soil full of compost or fertilizer. Healthy plants are most likely to resist powdery mildew.
Q Help me with my begonias. The leaves looked a little shiny and when I touch them they feel sticky. This doesn’t seem normal. Your advice? GJ, Tacoma
A. Sticky leaves are most likely honeydew, a cute little name for insect droppings. There are three sucking insects that attack begonias: aphids, mealybugs and whiteflies. If you see aphids on the tips of the new shoots, pinch off their bodies, or simply pinch off the new shoots if they are covered with aphids. If you see whiteflies fluttering around the plants when you water them, spray a mild insecticide under the leaves where the whiteflies have made their breeding grounds. Another option is to remove the infected plants and start over with plants that offer fresh fall color. Local nurseries will soon be filling up with late summer and fall color. If annuals are having problems at the end of summer, that’s sometimes a sign to rip them out and try something new for a late summer renewal.
Marianne Binetti has a degree in horticulture from Washington State University and is the author of “Easy Answers for Great Gardens” and several other books. For answers to gardening questions, visit plantersplace.com and click on “As an Expert.” This column is copyright Marianne Binetti. For more information on gardening, visit her website at www.binettigarden.com.
