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Gardening: Heat wave has upsides, but requires vigilance

Sat., July 19, 2014

Cilantro, parsnips and carrots all benefit from a thick layer of grass clippings that control weeds and reduce evaporation from the soil. (Pat Munts)
Cilantro, parsnips and carrots all benefit from a thick layer of grass clippings that control weeds and reduce evaporation from the soil. (Pat Munts)

Summer has arrived in the Inland Northwest with a vengeance. While the tomatoes, eggplant, squash and peppers love the heat, they don’t like the dryness. Neither does the rest of the garden.

The biggest challenge right now is adjusting your sprinkler systems and other water devices to meet the needs of the plants in 90-degree heat. First, check your heads, especially on drip irrigation systems. Look for plugged heads and leaking lines and fix them. Otherwise the only way you will know there is a problem is when the plants start dying, and by then it’s too late.

The dry heat and wind pull a lot of water through the plants, so increase the frequency of irrigation. First check how deep the water is getting in the soil by digging 6-inch deep holes. A bulb planting tool works well for this. If the soil is damp at the 6-inch point, hold off on increasing the water. If it isn’t, increase the watering intervals and times. How frequently will be depend on how much clay, sand and organic matter you have. Sandy soils will need more frequent irrigation than clay soils. Soils high in organic matter hold more moisture for longer periods.

Add mulch to any open soil areas in your vegetable or ornamental beds to help keep the moisture from evaporating from the soil and to keep it cool. Weed the area well before applying your mulch to keep the weeds from popping up through the cover. Next spring, remember to apply mulches early in the growing season to save you time and energy weeding. Shredded pine needles, untreated grass clippings, bark and compost all make good mulches.

One advantage of these hot days is that the nights have warmed up to well over 55 degrees. Tomatoes and peppers need temperatures above 55 at night to set fruit. To help the plants release pollen either gently shake the stems with blooms or use an old electric toothbrush to vibrate the flowers, thereby releasing pollen. The downside of this is that if the temperatures during the day get to the mid-90s and above, fruit set will be disrupted.

Most cool season crops like lettuce, peas, spinach and kale can’t tolerate the heat and will begin to wither in the heat. Spinach and lettuce are likely to bolt or go to flower as the days begin to shorten. The best thing to do is pull out those crops and plant a cover crop in their place until early August when it will be time to plant fall crops. Good cover crops include buckwheat, field or Austrian peas or oats. Buckwheat is especially good because it has a lot of organic matter and the bees love the white flowers.

Now is a good time to give most vegetable crops a dose of fertilizer as they begin growing quickly. Scatter the fertilizer on the soil under the plants and water it in well. Don’t work it into the soil as this will damage shallow plant roots.

Pat Munts has gardened in Spokane Valley for more than 35 years. She can be reached at pat@inlandnw

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