I know July is summertime, but this is ridiculous. We live in Colorado at an elevation of 7,000 feet. Yet day after day the temperature climbs into the 90s (tomorrow’s forecast is for 97°). I always though we’re too high to be this hot!
As I sit here in front of a fan, lemonade in hand, I can see my garden out the window. Of course the lettuce is bolting (as I mentioned last week). The cilantro is in full bloom, with delicate white flowers that attract a variety of beneficial insects. The bok choy is blooming too. Its bright yellow flowers of four petals arranged in the shape of a cross declare that it’s a crucifer, or mustard family member.
In this heat, keeping things watered is essential. Last week we had hours of rain. This week all that mud is baking into pottery. Mulches help, and the soil is still damp where a thick layer of straw shades it from the hot sun.
Knowing when to water is a learned skill. Yesterday around mid-afternoon, with the thermometer reading 96°, the squash leaves hung limply draped over the stems. However, early this morning when I went out to water before the heat of the day, every leaf was erect and crisp. When I stuck a finger into the soil, it was damp at two inches and below. The squash wasn’t really dying, it was merely wilting to reduce water loss through its leaves.
In the next bed, however, a block of chard still looked a bit wilted even in the relatively cool morning. The mulch is thinner here, and sure enough, the soil was dry. I gave the plants a good drink and made a mental note to add more straw around the root zone.
Green beans are a handy “indicator crop” when it comes to watering. When they begin to dry out, the leaves are held vertically on the stems, reducing the surface exposed to direct sunlight. Their color shifts from bright green to a more muted green-gray. To keep your plants flourishing, it’s important that they are irrigated before they actually wilt.
Erratic soil moisture plays havoc with many crops. If allowed to dry out, carrots and radishes can’t expand fast enough when water is again available. The roots crack as they swell, ruining their appearance. Tomatoes have the same problem, although in their case it’s the fruit that cracks. Lettuce suffers problems with calcium uptake, resulting in “tip burn.” In all cases, flavor suffers, and our tender veggies become tough and stringy.
On the other hand, watering already-damp soil can rot roots. Remember that roots need air as well as water, and continued soaking fills up all the air spaces between soil particles. To allow for soil/air exchange, it’s best to allow the top of the soil to dry before irrigating again.
As I’ve mentioned many times, it’s best to water the soil, not the plant leaves. Many soil-borne diseases can be avoided simply by keeping any dirt off the foliage. Plus, water applied to the leaves can act as a lens for the burning sun. Besides, we want the water to reach the roots rather than evaporate and be lost.
This morning I happened to use the hose to apply water exactly where I needed it, rather than to the entire garden. The hose had been laying in the sun, and the water inside actually burned my fingers. Be careful; water that hot will also burn the plants.
In spite of the heat and (for Colorado) high humidity (it was at 78% the other day!), many of my plants just aren’t doing all that well. Plant growth occurs in an optimal temperature zone. Too cold, and the chemical reactions necessary for growth happen very slowly if at all. But too hot, and the plants can’t grow either. Of course, different crops have different requirements. But this year, with its cold spring, sudden heat, drought, then heavy rains and hail, and finally even worse heat—well, it’s hard on everybody.
Just as we choose resilient plants for our landscapes, Colorado gardeners have to be resilient too. So my peas only got a foot tall (I picked about a dozen snap peas last week, and that will probably be all I get this year). So the lettuce is turning bitter and the chard is still struggling to grow new leaves after last week’s shredding. Gardeners at heart are an optimistic lot. Maybe I’ll go start some cabbage for fall!