A scary weather forecast for record-setting high temperatures this week, lingering over a longer than usual period, should send you out to the garden today to take some simple steps to protect your vegetables. Basically it boils down to 3 things: Shade, water, harvest.
Of course, shade cloth, which I have discussed in detail earlier is a very handy tool to have, but you can use anything from curtain material to paper to old sheets if you have to. A reminder that floating row covers and insect netting do not shade or cool beds. If you have covered carrots or other vegetables to prevent insect attack, lay shade cloth or a light weight fabric on top of the insect barrier to shade beds if you have small seedlings (as you would right now if you sowed carrots earlier this month).
Mature plants now generally have leaves well adapted to sun and their leaves also shade and cool the soil for roots. Priorities for shading this time around are the Brassica family (broccoli, cauliflower, cabbage, etc.), lettuce and leafy greens, peas and all seedlings and young plants from summer plantings. Don’t forget to shade greenhouses and tunnels as temperatures inside will be high enough to kill flowers and may injure the exposed sides of tomato, cucumber, pepper fruit (lay a piece of paper or cloth over fruit in direct sun avoids sunscald). Of course, if you are growing yams/sweet potatoes, they will feel that things are finally going their way, so just keep them watered and let them enjoy the heat. If you have started seeds in flats, these just won’t be able to cope with the heat so should be kept in the shade of a tree during the middle of the day. If possible, try to set the flats out where they can get a bit of full sun early in the morning and again in the evening so they don’t get too leggy.
If you have a good water supply, be generous with irrigation. For the rest of us living in water districts or municipalities with summer watering restrictions, do what you can within the limits you are allowed. To scrounge up more water, you can safely use kitchen water from rinsing dishes, washing vegetables and clean shower water (use a bucket to collect the first water you run while waiting for the water to warm up). If you can’t water, shading plants helps a lot: heat plus dry soil devastates plants and causes a lot of injury, whereas dry soil is not nearly so damaging if plants can be kept cooler. At the expected temperatures, our garden veggies won’t be able to photosynthesize anyway (most have an upper limit in the range of 28-34oC or 82-94oF) so being shaded for a few days isn’t going to make things worse.
Time for preventative harvesting: If you have lettuce, endive, broccoli, cauliflower, bok choi and other leafy greens ready it is best to pick as much as possible now and keep the surplus in the refrigerator until you can use it. These crops deteriorate quickly in hot weather: I am always surprised at how quickly a promising head of cauliflower can turn into a strong flavoured, distorted head and how quickly lettuce and leafy greens go to flower.
Late July to early-August is generally good timing to sow fall and winter lettuce, winter radish/daikon, leafy greens of all kinds, spinach, broccoli raab, more kale, kohlrabi, white turnips. BUT, you might want to wait to sow these crops until this heat wave is over.
Once you have taken steps to protect the garden—do go jump in the lake or head for the beach! Stay cool everyone…