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updated: 8/11/2014 12:52 PM

The vagaries of the late-summer garden

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The Washington Post

The Post's gardening columnist Adrian Higgins answered questions recently in an online chat. Here is an edited excerpt.

Q. My giant dill has gone to seed and will soon be ready to harvest. Last year I saved the seeds in a paper bag to fully dry, but when I opened the bag, I realized that some of the "seeds" were moving -- bugs! How do I avoid bugs this year? Should I just leave the seeds out on a paper towel until I'm sure they're dry and bug-free? Is a glass container the best way to store the dill seed in the kitchen?

A. If seeds are fully ripened and allowed to dry before storage, spread them on paper in an air-conditioned room for a week or so; they can be stored in the freezer. This will kill most bugs and their eggs, but not the seeds. Give it a go.

Q. I had planted two heirloom varieties of tomato obtained from a farmers market vendor; they seemed to really start to struggle in a heat wave and now most of the nine are mostly dead. Various parts of the plants turned yellow, then shriveled up and turned dead brown. Am I crazy to think I could attempt again next year with better varieties -- I've had other types do better than this! -- being more generous with the water via drip lines from Day One?

A. I'm a fan of heirlooms and their stories, but many simply don't have the inbuilt disease resistance of modern hybrids. Yours may have suffered from late blight, which is a killer. Most tomatoes around here (the Mid-Atlantic area) suffer from a less pernicious disease called early blight, which causes the lower leaves to yellow. Good sanitation is essential with early blight, however. You should remove the leaves from the bed entirely (throw them away, don't compost them). Late blight causes blackening of leaves and stems and collapse of the plants. The rule of thumb for any morose veggie plant is to pull it, clean up the leaves, evaluate whether the site or the cultivation contributed to the malaise and alter things for next year.

Q. I have had a decent crop of green zucchini, but the leaves are starting to turn white and fewer zucchini are growing. Is the plant dying? Should I pull it and plant something new? If so, what would be a good replacement for this time of the season?

A. This sounds like powdery mildew, which will eventually weaken the plant to a point where it struggles to flower and fruit. Once it appears, it is nigh impossible to reverse and it is better to pull the plant. There must be other gardeners begging to unload their zucchini. You could plant bush beans in its stead, or sow kale for the fall; that's what I'm doing this weekend.

Q. What's your feeling about glyphosate? I've always understood that it was one of the more benign herbicides, because it's supposed to evaporate quickly, and I don't know what else I can use to keep down the pokeweed that the birds sow so liberally in my two-thirds acre.

A. I prefer to handpick or hoe weeds, but there are times when herbicide is the only option, and glyphosate, the active ingredient in Roundup, seems to be one of the least toxic. I have a wormwood established in an embankment, and I keep cutting it back and it keeps growing, and I'm now on the verge of using glyphosate on a paint brush to target it without bothering plants around it. Old pokeweed develops huge tubers; I think you would need many repeated doses of glyphosate to kill the entire plant. I would dig it out with a mattock.

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