Emmalea Ernest, Extension Fruit & Vegetable Specialist; emmalea@udel.edu
By this time most warm season vegetables have already been established. However, if you are putting in plantings in late June and July, high temperatures and long, sunny days can make it challenging to establish transplants on black plastic mulch. On hot, sunny days, heat builds up in black plastic mulched beds. Very hot air moves from under the plastic out through the transplant holes. When that hot air hits the transplant stem, necrosis, girdling and plant death occur. We tend to see this problem most often with peppers.
There are several strategies you can use to protect transplants from heat necrosis.
- Use larger transplants (i.e. 72 cell size rather than 128) that will have thicker stem diameters.
- Make sure transplants are not water stressed during establishment.
- Make a larger hole in the plastic when transplanting and make sure that the transplant stem is in the center of the hole, not touching the plastic.
- Reduce bed temperatures temporarily by using shade cloth or by spraying white particle films (clay or lime based) over the mulch.
- Reduce bed temperatures for the entire growing season by using white, rather than black mulch
Pepper and tomato transplants that were girdled by heat necrosis.
Black plastic mulch has been sprayed with particle film to protect eggplant transplants from heat necrosis.
In 2022, shaded peppers planted on June 1 had much better establishment than unshaded ones.