Q. Are there any vegetables or herbs that I can plant now, in the middle of summer? Some of my summer vegetables died in the heat, and I would like to replace them.
Generally speaking, I don’t recommend planting anything new in the garden this time of year. Even if we get a few days of respite from the heat, it’s likely to get toasty with short notice. I understand the urge to replace lost plants so you can get at least a modest harvest before the end of the summer growing season.
Most herbs and vegetables come in either six-packs or small pots (4 inches). This means that the root mass is going to be too small for the size of the plant. If planted directly into the ground, they are likely to fail since the top growth is too much for the root mass. One way to get around this is to immediately transplant these small starts into a 1-gallon container and keep them in a sunny but sheltered spot for several weeks. Keep the pots watered, and the roots will eventually fill out the gallon pot. Pick a day when the weather is supposed to be relatively cool and plant out in the garden then. Keeping them in larger pots allows the plants to acclimate and build up healthy roots that will allow them to tolerate the heat better. After planting in the ground, don’t forget to water daily and mulch heavily. Hopefully this will allow you to harvest until late fall or early winter.
Q. At what temperature do tomatoes stop producing fruit or flowers?
Tomatoes are at their happiest when the daytime temperatures are between 65 and 85 degrees. Once the temperatures go over 95, the plants go into siesta mode (they will stop growing, setting fruit, or flowering). When exposed to intense sun, the fruit can become sunburned. Plants can also become water-stressed, making them more susceptible to disease and pest damage.
Some varieties are better suited to Southern California heat. Look for Big Beef, Mortgage Lifter, Super Sweet 100, Cherokee Purple, Ace, and Black Krim. If your garden gets very intense sun, consider using shade cloth to protect the fruit from sunburn and the plants from stress. Mulch heavily and water regularly. After watering, check several inches below the soil surface since water penetration may not be as good as you think it is. Harvest fruit before a heat wave and let it ripen inside since exposure to temperatures over 100 degrees can adversely affect taste.