Near record breaking heat will have an impact on our garden’s vegetables. In general, daytime temperatures that exceed 92°F and nighttime temperatures above 72F will cause problems. The longer the heat lasts, the bigger the impact. Problems include:
Sunscald – Usually a problem with late season heat waves when loss of foliage is more prevalent, but any fruit exposed to direct sunlight can experience bleaching and browning of the exposed parts.
Pollination issues in cucurbits – Heat favors male flower production over female flowers, resulting in fewer fruits, at least temporarily. It may also lead to drop of already set fruit. Bee flights/activity is reduced in hot weather which causes poor pollination and flower drop. In some cases, fruit will be distorted and crooked due to incomplete pollination. Cucumbers are especially sensitive to this disorder.
Tomato/Pepper flower drop – Flowers on these plants have a 48-hour window to pollinate. High temperatures can cause pollen sterility and flower drop. You may not notice the impact until 5 to 6 weeks later when yields are suddenly reduced for a period that aligns with the length of the heat wave.
Sweet corn yields – Although a heat loving crop, daytime temps over 95F can result in poor tip fill, missing kernels, smaller ears, and reduced yield.
Snap bean flower drop – Beans respond by dropping flowers. As soon as temperatures cool down, flowers will develop normally. Unfortunately, this may result in a split set, where some flowers set before the heat and others after. This is a big problem for one-time mechanical harvest but doesn’t have much impact on garden grown beans. Read more Heat and Garden Vegetables