'None Like it Hot'; When Even Sun-Lovers Need Some Shade
Q. Greetings! I used to garden when I was much younger and I'm ready to try again now that I understand more of the do's and don'ts. One thing you will find though, if you come here in the summer, is that it can get swelteringly hot. I plan to do some extensive container gardening in my treeless (and nearly shade-less) backyard, specifically tomatoes, peppers, cucumbers, and zucchini. What can be done to help my poor plants get through the hottest times of the year?
P.S.: your online questions and answers have already helped me get a leg up on my preparations! Thanks!
---Matthew in Memphis, Tennessee
A. Matthew is correct. The classic "Boys of Summer": Tomatoes, peppers, zukes, cukes and the like need six to eight hours of sun a day to reliably produce good fruits, but too much sun can be damaging, causing problems like cat-facing and sunscald. And heat that stays up in the nineties can cause total lack of fruit if the heat cooks the pollen on the plants, which can be a big problem, especially with tomatoes.
Now, this generally isn't an issue in the North, Midwest and Mid-Atlantic, but it does affect many parts of the South and Southwest. So much so that tomato growing season pretty much excludes the months of July and August in torrid areas like USDA Zone 9 and above. It's just too hot for people and plants at that time of year.
And does container growing make things worse?
Yes, and the smaller the container the more dramatic the effect, so use the biggest containers you can find and keep them well-watered. Learn how to 'rock' smaller containers to judge their water needs; if they move easily they need water; if they stay locked in place they're probably still saturated. For bigger containers use a moisture detector or shove a thin wooden dowel deep into the soil to judge where the 'water line' ends.
Now, in general we always stress that the roots of plants need to dry out in between waterings, and watering every day would be death for plants in the ground, even in a hot and sunny region. But plants in pots don't have the insulating effect of being underground and may need to be watered daily. Or it could be weekly. You need your head in the game here.
And then there's the type of container: terra cotta pots look nice but wick their moisture into the air and dry out quickly. Plastic pots and other non-clay containers hold their water much better; and big containers like half whiskey barrels are the best. The large volume of soil they hold greatly mitigates the container effect. And wood isn't going to heat up in full sun.
Right—sun. So don't use black plastic pots.
What about metal containers?
They're going to absorb and hold heat; and they might even burn you if you touch them on a "Mad Dogs and Englishmen" afternoon. Anyway, always try and water your containers (and everything else you might be growing) in the morning—slowly if they're dry.
Give each container a little drink to get started and then go back and repeat the small amounts in succession until you see water coming out the base of all the containers. If you just dump a lot of water quickly into a dry pot it'll all run out the bottom.
You can even water in the early evening as long as you don't wet the leaves of the plants But you should mist the leaves in the morning, especially if you garden in an area of low humidity, to replace the dew that would otherwise refresh the plants.
OK. It is now time to 'throw some shade'.
If your plants are baking in full unrelenting sun, rig up some shade. It can be anything from professional shade cloth to a retractable tarp on home-made support to a bunch of beach umbrellas that you or a friend open and close. You still want the plants to get six to eight hours of sun, so your choices would be to bring the shade into play around 3 pm; or, if you're there to take care of your plants during all day, provide the shade from around 1 to 4 pm. No; not everyone can do that, but it is ideal.
Maybe there's a school-age kid nearby you can hire to be your 'plant protector'. Or, if you have to work every day and have no help, give the plants a day off every third day during serious heat waves by shading them all day to replicate a naturally cloudy day. Be creative! Think about what's going to work for your schedule and situation; and most of all, keep an eye on your plants. Watch for signs of stress and be prepared to change tactics.