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Originally published Thursday, September 12, 2013 at 5:04 AM

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Preventing blossom end rot, and washing whiteflies away

Garden writer Ciscoe Morris advises calcium to prevent blossom end rot on tomatoes, and advocates for an environmentally friendly way to combat those pesky whiteflies but protect the insects that prey on them.

Special to The Seattle Times

Gardening Events

Ciscoe’s Picks

Northwest Horticultural Society Annual Fall Plant Sale: noon- 6 p.m. Sept. 20 and 9 a.m.- 2 p.m. Sept. 21. Plants from specialty growers. North Seattle Community College, 9600 College Way N., Seattle; (www.northwesthort.org)

Northwest Perennial Alliance Lecture: “Fern Frenzy”: 1 p.m. Sept. 22 (doors open at noon for seed and plant sales). Speaker is Judith Jones, an NPA founding member. Molbak’s Nursery, 13625 N.E. 175th St., Woodinville; (www.northwestperennialalliance.org)

Fall Backyard Habitat Classes at Woodland Park Zoo: First class of five is at 7 p.m. Sept. 25. Master birder Neil Zimmerman of Seattle Audubon will teach participants how to attract and care for birds through plant selection, gardening practices, bird feeders and water features. Woodland Park Zoo Education Center, 750 N. 50th St., Seattle; $25/class or $100/series (www.zoo.org/backyardhabitat).

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In the Garden

Q: My tomatoes are all turning black on the bottom. How can I cure my tomato plant so that I can get a few decent tomatoes?

A: Your tomato has blossom end rot, which turns the bottom of the tomato black and leathery. It isn’t a disease; it’s caused by a lack of calcium and is a lot easier to prevent than to treat. The problem can usually be avoided by incorporating calcium-rich agricultural limestone into the soil in fall to give it time to break down into a usable form in time for spring planting. It’s also a good idea to add a handful of calcium-rich bone meal under each tomato at planting time. This is especially important when growing tomatoes in pots, as soils in containers are quickly depleted of calcium. Even with adequate amounts of calcium available, however, the plant won’t be able to absorb it if the soil is allowed to become too dry between waterings, or if a salt buildup occurs from using too much synthetic fertilizer. Keep the soil evenly moist, and fertilize only once by mixing in a cup of organic vegetable food at planting time. Unfortunately, once the problem occurs there isn’t much you can do to solve it. Although often recommended by garden experts, research shows that foliar applications of calcium and/or Epsom salts does little good. The best thing you can do at this stage is to water carefully to keep the soil evenly moist. The good news is that you don’t need to toss the affected tomatoes in the compost bin. Just cut off the black part and eat the top — it’s totally unaffected and will taste just as delicious as the entire tomato would have.

Q: I’m totally frustrated by whiteflies in my mixed border. Is there any surefire way to get rid of them?

A: Whiteflies are indeed frustrating pests. They’re easy to identify because the adults fly around in enormous white clouds when they’re disturbed. The damage they cause is similar to that of aphids, including deformed new growth, wilting, yellowing leaves, and profuse honeydew that usually gets covered with an ugly black fungus known as sooty mold. These insects are notoriously difficult to control. They have multiple generations per year, and the immature insects turn into little blobs that glue themselves to the bottom of the leaf and are covered with waxy hairs that protect them from most sprays. Although pesticidal soap and oil sprays can help control whitefly, you’re better off regularly blasting the insects off the plant with a powerful spray from the hose. A blast of water will drown the adults, but as is true of soaps or oils, it won’t harm whitefly in the waxy immature stage. The best reason to use water rather than soaps and oils is that water is less likely to harm parasitic wasps, one of our greatest allies in the battle against whitefly. These tiny wasps lay their eggs in the bodies of the immature stage of whitefly, which soon hatch and devour their host. If all goes well, they can parasitize up to 95 percent of the immature whiteflies on a given plant. Take a look under the leaves to see if a significant number of the normally pinkish waxy blobs have turned black or bluish. If that’s the case, parasitic wasps are indeed helping you out.

Ciscoe Morris: ciscoe@ciscoe.com “Gardening With Ciscoe” airs at 10 a.m. Saturdays on KING 5.

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About Ciscoe Morris

Ciscoe Morris' column runs Thursdays. His show "Gardening with Ciscoe" airs at 10 a.m. on Saturdays on King 5.
ciscoe@ciscoe.com

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