Planting Tomatoes in Seattle: A Guide to Optimal Growth

when to plant tomatoes in seattle

Seattle’s temperate climate presents an excellent opportunity for growing tomatoes. However, understanding the optimal planting time is crucial for ensuring robust germination and abundant yields. In this article, we will explore the ideal conditions and strategies for planting tomatoes in Seattle.

Planting after the Last Frost Date

Planting Outdoors

If you plan to sow your tomato seeds instead of purchasing seedlings, the best time to do so is after the last frost date. Seattle’s tomato growing season typically begins around March 17, coinciding with the end of frost. With warmer and more stable temperatures, this period presents an ideal opportunity to plant tomatoes outdoors.

Planting Indoors


For those who wish to start early or grow tomatoes with long growing days, starting seeds indoors is an option. Begin planting your tomato seeds six weeks prior to Seattle’s average last frost date. For example, if the last frost date is around March 17, sow the seeds on February 3 for optimal indoor planting. Wait until the freezing phase ends before transplanting the seedlings outside, ensuring they are safe from unexpected ice. Generally, move the tomatoes outside around March 24 for a secure planting time.

When transplanting tomatoes outdoors, it is essential to acclimate the seedlings to the outdoor temperatures gradually. Expose them to the outdoor environment for a few hours each day for at least five days before moving them permanently. This conditioning will help the seedlings thrive in their new surroundings.

Further reading:  How to Make Your July Garden Thrive

Sowing in Suitable Temperatures


The ideal time to plant tomatoes in Seattle is when the soil temperature ranges between 55-85°F, and the air temperature measures 65-85°F. These moderate and warm conditions support optimal tomato growth. Planting tomatoes in excessively hot weather can lead to diseases like sun scald and difficulty in fruit production, while planting in extremely cold conditions may cause rotting. Therefore, it is crucial to wait until the soil and air temperatures align with these suitable ranges before planting tomatoes.

To warm the soil effectively, consider using raised beds constructed with materials like stones or cement that absorb and retain heat better than wood. Greenhouses with glass walls are also excellent options as they trap heat and create a warm environment favorable for tomatoes.

Tomatoes, Thriving in Seattle


Seattle’s mild air and soil temperatures from spring until fall provide an ideal setting for tomatoes to thrive. However, to ensure successful growth and a bountiful harvest, it is important to choose tomato varieties with short maturity days. These varieties can be harvested before the arrival of rainy and cool October days.

Wintering Tomatoes

Tomatoes are perennials that can survive the winter and be replanted in the following spring for a fresh yield. You can bring them inside your home or place them in a greenhouse to protect them from the frigid outdoor climate. Follow these steps to winterize your tomato plants and preserve their life during the dormant period.

Caring for Tomatoes

To ensure the health and productivity of your tomatoes, it is essential to provide proper care. This includes regular watering, fertilization, pruning, and pest control. By implementing these practices, you can maximize the yield and enjoy a bountiful harvest of delicious tomatoes.

Further reading:  The Joy of Repotting Spider Plants


In conclusion, when it comes to planting tomatoes in Seattle, timing is crucial. The warm temperatures of March in spring present the best opportunity for optimal tomato growth. Remember to use techniques like warming the soil in raised beds or utilizing greenhouses to create an ideal environment. By following these guidelines, you can achieve healthy yields and enjoy the satisfaction of growing your own tomatoes in Seattle.

I hope this article has provided you with valuable insights into when and how to plant tomatoes in Seattle. For more information, visit the Ames Farm Center. Thank you for reading!