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Cool Season & Warm Season Crops

Our maritime climate allows us to grow edible crops year round, but certain crops require warmer conditions and longer sun exposure that only occur in the summer months. Let’s explore cool season crops to enjoy now and how to prepare for the transition to warm season crops.

Cool season crops are typically planted in the “shoulder seasons” — spring and fall — when the days are shorter and the temperatures are cooler because they either thrive in or tolerate such conditions. In the spring, cool season crops are typically planted out in March through May.

  • Seed or transplant into the garden when temperatures are 40-60 degrees. 
  • Some will continue growing as temps rise, but others might quickly reach the end of their life cycle (often called bolting) as they receive too much light or warmth for their liking.
  • Leafy greens like lettuce, kale, chard, mustards, spinach, herbs like cilantro and parsley, some root veggies like beets, parsnips, radishes and carrots, as well as legumes like peas and clover are all considered cool season crops. 
  • Interplant various types of cool season crops to mitigate pest pressure. Bunnies prefer clover over lettuce!
  • Harvest these crops just in time to make room for warm season planting. 
  • Consider leaving some cool season crops to go to seed. Their flowers support beneficial insects in the spring and the seeds from successful crops can be saved for future planting.

When the ambient and soil temperatures are consistently above 60 degrees, the garden is ready to support warm season crops. Warm crops planted too early may be stunted or fail, and planted too late they may not have enough time to fully mature. It’s a different dance each year, depending on the weather patterns.

  • Watch the weather and plan to plant warm season crops in the garden in mid May through June.
  • Warm season crops can be started indoors with a grow light and (optional) heating pad. As the temps continue to fluctuate, try “hardening off” the young plants by taking them outdoors during warm sunny times, then bringing them back inside during the coolness of the night. 
  • Consider setting up a cloche or hoop house to support tender warm season starts. A plastic or row cover awning helps keep cold air from settling on the bed at night and helps accumulate warmth during the day. 
  • Short-season varieties are ready to harvest in 65 days or less, and long season varieties can take 90 or more days to mature.
  • Warm season crops to try: beans, squash, tomatoes, cucumbers, basil, eggplant.
Consider setting up a cloche or hoop house to support tender warm season starts.

About the Author

Alex Soleil (they/she) is a Garden Education Specialist at Tilth Alliance. They’ve been tending a plot and community projects at Picardo Farm P-Patch in NE Seattle for over a decade.