When to Plant Tomatoes in Seattle? Things to Know!

Written by

William Golder


Dorian Goodwin

when to plant tomatoes in seattle

The fun thing about planting tomatoes in Seattle is that the city has a temperate climate that tomatoes love the most.

However, although the weather in this area is tomato-welcoming, we cannot deny that it still has unfavorable periods that might hinder proper growth.

Therefore, knowing when to plant tomatoes in Seattle is essential for robust germination and abundant yields. Temperatures between 50° and 85 °F and after the last frost date are optimum.

Plant tomatoes after the last frost date

Planting outdoors

When to plant tomato starts? If you plan to sow your seeds instead of buying seedlings from nursery, the best time to do it is after the last frost date.

The tomatoes growing season usually starts around March 17 in spring because the frost ends during this time.

Given that temperatures will have gotten warmer and more stable over this period, this month and season make it the ideal time to plant tomatoes outdoors.

Planting indoors


However, if you want to start early, especially if you plan to plant tomatoes with long growing days, you can do so by sowing the seeds indoors.

The best way to start tomatoes indoors Seattle is to plant them six weeks before the city’s average last frost.

For instance, since the last frost date in Seattle is around March 17, count six weeks backward and sow seeds on February 3 for optimum indoor planting.

Once the freezing phase ends, give your seedlings another week before transplanting them outside to ensure that there will be no unexpected ice.

In other words, move tomatoes outside around March 24 for a safe planting time.

Let seedlings get used to outdoor conditions.

When transplanting tomatoes outdoors, it is essential to help your seedlings adapt to the temperatures outside your home.

Thus, bringing them outdoors for a few hours for at least five days before moving them to their new environment is a big help in conditioning them.

Read more: Best time to plant tomatoes in other states like North Carolina, Ohio, and Michigan,…

Sow tomatoes once the soil temperature ranges between 55-85°F and the air’s 65-85°F.


It is a sign that you can plant tomatoes outside if the soil temperature reaches between 55-85°F and the daytime air measures 65-85°F.

Wait until the temperatures become suitable for tomato planting.

Moderately warm weather is ideal for these crops’ growth. They will develop diseases like sun scald and have a hard time bearing fruit in hot weather, while excessive cold can cause rotting.

Therefore, it’s crucial to wait until the soil and air conditions become ideal before you grow tomatoes in Seattle.

Strategize to make the soil warm.

Various ways can help your soil become warm, especially if frost has just passed.

  • Covering the soil with clear instead of dark plastic at least three weeks before sowing seeds is an effective way of trapping the heat.
  • But if you prefer not to put something on top of the ground, you can plant tomatoes in a raised bed instead.

The soil in raised beds warms up swiftly, since they are the first to receive sunshine and absorb it faster than the ground.

This technique is much more effective if you use stones or cement to build a plant bed because these materials trap heat better than wood.

  • Alternatively, if you have a greenhouse, gardening there is also an effective way to improve the heat of the soil and air.

The glass walls in greenhouses invite the heat to enter quickly and keep it in, making the high temperature circulate the premise.

Do Tomatoes Grow Well in Seattle?


Yes, the mild air and soil temperatures from spring until fall make tomatoes thrive well in this area.

However, one thing you must consider for achieving successful growth and yield is sowing a variety of tomatoes that fit the city’s planting period.

The best tomatoes to grow in Seattle are those with short maturity days, which you can harvest before the rainy and cool days of October arrive.

  • Sungold and Juliet are some cherry tomato varieties that grow well in the city because aside from their sweet taste and juicy texture, they have short growing days of 60.
  • The Bloody butcher type is also a favorite of many because it bears lots of fruits and only needs 55 days to grow.
  • Big beef is also an excellent example to grow because it can cope well with diseases and only needs 73 days to mature before harvest.

How to Make Tomatoes Survive the Winter?

Tomatoes are perennials that can survive winter and be replanted in the following spring for a new bloom in the year.

Bringing them inside your home is one way of wintering tomato plants to preserve their life as they go dormant over the winter.

If you have a greenhouse, it is another good option to place them there to protect them from the frigid climate outdoors. Follow these steps for overwintering your fruits.

  • Stop watering for a while before bringing the plants inside.
  • Place them near the window for them to get enough sunlight.
  • Surround the tomato plants with mulch to keep them warm from the cold.
  • Once spring comes, remove the mulch and prepare to move tomatoes outside once the temperature increases.

How to Take Care of Tomatoes?

  • Plant them in an open area where they can get 6-8 hours of sunlight.
  • Sow them in well-draining soil.
  • Give your tomatoes lots of water once a week to keep them moist.
  • When the temperatures are high, irrigate them more often than usual.
  • Use organic fertilizer to feed your plants once a month, especially when fruits are developing.
  • Harvest your tomatoes once their color becomes more vibrant to enjoy the best texture and taste.


It is undeniable that tomatoes are a little selective regarding the planting time because they only thrive in warm temperatures.

Usually, around March in spring is when they thrive the best. That’s why it is essential to sow them in this period.

Always remember to use clear plastic to cover the ground or place the tomato plants in a raised bed to make the soil warm and workable.

I hope you learned a lot about when to plant tomatoes in Seattle and how to have healthy yields. Thank you for reading!

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