Summer heat often means poor yields

Stating the obvious is sometimes irresistible: It’s hot outside. Broiling hot. At 6 a.m. Monday one of our thermometers was already registering 82 degrees, in a string of days in the high 90s. While the temperature is one thing, the meteorologists like to emphasize the heat index to let us know that our misery is really more intense than we think. If we adopt their ultra-pessimistic view, we can envision ourselves gardening in Death Valley this week.

On Sunday I paid a worried visit to my garden to check on my veggies. A day earlier the soil had still been damp enough from last week’s rains that I had waited to pull the weeds that sprouted after the precipitation.

What a difference a day makes. While everything remained green and lush, the soil had dried out considerably. Even with the drenching rains last week, I am likely to be turning on the hose in a couple of days.

When the weather turns scorching hot, expect the production from your vegetable garden to slow. Most varieties will not set new fruit when the temperatures get stuck in the 90s. Tomatoes top the list here. Even if your plants are covered with blossoms, they are in survival mode and are diverting all of their energy to battling the heat.

As a result, this heat wave is likely to deplete the number of tomatoes you’ll be able to pick in mid-August. Depending on how long the heat wave lasts, the fruit on the plants now may be the bulk of your harvest. Even so, it’s important to keep the plants healthy and well-watered to support the fruit they do produce. Also, healthy leaves will protect ripening fruit from sun scald, which is a real danger under current conditions.

Beans, melons, cukes and squash also will slow production during extreme heat – but not my faithful okra. My family is going to be sick of eating it every day long before this year’s crop cashes it in.

I theorize that a couple of things are going on here. First, okra is as tropical a vegetable as we grow in North America. It thrives in extreme heat and can endure periods of low rainfall better than anything else in the garden. Treat it right, however, and it will outperform anything in the garden.

This brings me to my second okra point. Earlier this summer I tried several suggestions from readers about how to repel rabbits that were eating my bean plants. One of them was to sprinkle blood meal, a nitrogen-only fertilizer, around the bean plants. The okra was nearby, so I fertilized it, too.

As a result, my okra plants have large, lush leaves that shade the yellow and red blossoms and the emerging pods on the stems. While okra is heat-hardy when left to its own devices, I strongly suspect that the leaf cover is contributing to this year’s output.

Meanwhile, our approach to watering may need to change in high heat. It’s always a bad idea to water a vegetable garden with a sprinkler or a sprayer, but it’s a really bad idea to do it in extreme heat. When moisture, with or without chemicals, is left on the leaves, chances are the sun will bake it into the leaves before the plant has a chance to absorb it. This can contribute to a scalding effect on the plant.

Tomatoes, in particular, for which leaf health is so important, can respond badly to this. Sorry, Miracle Grow fans, a cohort that includes many of my readers. You would be well-advised to stow the hose attachment in the shed until the temperature drops. In the meantime, mix your solution in milk jugs or buckets, and water the roots only.