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Annuals Seed Starting Calendar

Hardening Off: Tender seedlings started indoors will need a gradual introduction to the cooler temperatures and environmental elements of the outdoors. “Hardening Off” is the process by which you can accomplish that!

How to “Harden Off”

  • As the weather gets nicer, start putting plants outside during the day and bringing them in at night. This helps to acclimate them to cooler temperatures.
  • Bring plants in during the day if temperatures are to reach freezing (or even near-freezing), as this may be too cold for most seedlings.
  • It takes about 2 weeks for your plants to be “hardened off,” and this process should be completed before transplanting.
  • Once hardened off, some plants can withstand a light frost. Plants that are more tender to frost to near frost conditions may have to be brought in at night until mid to late June, once the threat of frost has passed. They will reflect a later transplanting date in the chart below.

View the calendar below, or download the PDF version here!