In spite of a few cooler days and nights and a couple of days of light rain, the heat and drought continue to make this one of the most difficult growing seasons in recent memory. Most of the time I have spent in the garden has been spent watering, leaving little time in the cooler hours of the morning for weeding and other garden chores. And in spite of my efforts to keep everything watered, I notice that flowers are blooming and fading faster than usual and that my vegetable yield is much less than in the past. There are other heat and drought related problems affecting our gardens than just keeping them watered.
Many vegetable gardeners are reporting that while their plants are green and lush they are yielding little or no fruit. There are a number of ways the heat could be contributing to that. One could be too much fertilizer– especially nitrogen fertilizer. Nitrogen aids in the development of green foliage, which explains a robust looking plant, but fertilizing during a drought places plants under additional stress. You should avoid fertilizing during periods of extreme heat. High day and night time temperatures can also contribute to flower drop (abortion). Flowers are formed but then they die and drop off. This generally occurs when temperatures are consistently between 75° and 95° which is what we have been experiencing for most of this summer.
Tomatoes are especially sensitive to the sustained high temperatures. Tomato flowers have a 50 hour window of opportunity for pollination. With sustained temperatures of greater than 85° in the day and 70° at night the plants become stressed and burn through their stores of energy quickly. The flowers that do form are changed so that they are harder to pollinate and the flower usually drops before it is fully pollinated. Green beans and other flowering garden plants may also abort flowers in high temperatures.
Vining cucurbits, such as squash, cucumbers, melons and pumpkins, can have their own set of problems with the heat. These plants produce separate female and male flowers. Female flowers are identified by a swollen stem directly below the flower, which is the part that will actually develop into the fruit. Male flowers have a straight stem below the flower. Daytime temperatures above 90° and nighttime temperatures above 70° result in the plant producing an abundance of male flowers and relatively fewer female flowers. In addition, bees don’t like temperatures above 90° so they are not doing as much foraging and pollinating in the high temperatures. Even when pollination does occur it may not be at a high enough level, resulting in fruit that is small or deformed or may even rot before it is fully ripe.
Another heat related phenomenon is tomatoes that are not ripening. This is probably the result of hot nights. Tomatoes ripen in two stages; the first stage being when they become mature and green, the seeds are formed and the area around the seeds turns soft and gelatinous. The second stage is when the tomatoes turn red. The ideal temperature for tomato maturation is between 68° and 77°. The pigments that turn the tomatoes red are not formed when the temperatures are greater than 85°. We have had a few cooler days and nights lately so that might help, but keep in mind that tomatoes generally take 6-8 weeks to fully mature and change color, so patience might be needed to see our tomato crops fully ripen.
Even if the temperatures seem to be abating, it doesn’t look like we will be seeing any relief from the drought any time soon. It may be time to make some decisions as to how to conserve water going forward. If you are going to decide which plants are going to get watered I suggest favoring trees, shrubs vegetables and perennials. Annual plants are reaching the end of their life cycle anyways so maybe it is time to let them go. Native perennials usually have deep root systems and are drought tolerant so they can get by with less watering (unless they are newly planted).
There may also be ways we can reuse water. If you have a rain barrel be sure to use that water before dragging out a hose. You may be surprised how much water is in your rain barrel after our recent rains. We can reuse water that we use to cook vegetables to water our plants- just let it cool and pour it on your container plants. (Avoid using water that cooked meats or bones as that might attract animals.) Dishwater with low levels of soap can also be used to water some of your plants–just be sure not to get the soapy water on the leaves as it may burn them. Lastly, try putting a bucket in the shower when you shower. You might be surprised how much water you collect that might otherwise have gone down the drain.
There is still hope for this difficult gardening season – we just have to change some of our practices, have patience and hope for better days ahead.