Early Transplanting

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Early warm season vegetables such as tomatoes and watermelons require protection when transplanted in April. The following are some consideration for these early plantings:

  • Plant in your highest elevation fields with the lightest soils first and avoid low areas and frost pockets.
  • Start planting only when a warming trend is in the forecast. This is when daytime temperatures are expected to increase during the week and nighttime temperatures do not drop below 40°F. Bed temperatures should be above 60°F. Do not plant on a cooling trend and avoid planting when cold, clear nights and high winds are in the forecast.
  • Also avoid planting if extended cold, cloudy weather is in the forecast. It is critical to have warm soil conditions after transplanting to allow roots to grow out into the bed quickly. In cold, cloudy conditions, plants shut down physiologically, little root growth occurs, and the existing roots on the transplant do not function well, thus increasing the risk for transplant stunting or transplant losses.
  • Target fields with well advanced (the tallest) rye windbreaks between each row for early plantings. Windbreaks reduce wind injury and desiccation of transplants and also reduce the loss of heat from black plastic mulched beds, thus allowing more heat to be accumulated during the day (to be released at night).
  • In areas without windbreaks, consider using floating row covers for cold sensitive crops for the first 2-3 weeks. Use wire hoops supports over the top of plants to avoid mechanical injury. Clear perforated plastic row covers also can be used to increase daytime temperatures and heat the plastic beds. However, clear row covers do not have the same insulating effect of floating row covers. Row covers may be required in addition to windbreaks in the earliest plantings.
  • Only use well hardened-off plants for early plantings. Plants should be acclimated to outside conditions for 5 or more days before transplanting.
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