Tomatoes like it hot! They are frost tender and need relatively warm temperatures to grow, set fruit and ripen.
Local gardeners, looking for vine-ripened tomatoes, often are disappointed when left with nothing but green tomatoes at the end of the summer.
If this sounds like you, don’t give up! You can grow tomatoes successfully in the Pacific Northwest with a few special considerations.
Select tomato varieties suited for our climate
Thousands of varieties of tomatoes are available to home growers through nurseries, catalogues and websites. Search for those known to do well in shorter, cooler growing seasons.
You probably know the difference between determinate and indeterminate tomatoes. Determinate tomatoes are bush-like plants that stop growing at a certain height; their tomato crop tends to ripen all about the same time. Indeterminate tomatoes are vine-like plants with fruit that ripen over an extended period.
Because determinate tomatoes are more compact plants, they are easier to protect from cold (see below); they also tend to produce earlier making them a good choice in shorter growing seasons.
For greatest success, select the quickest maturing varieties, focusing on those that ripen in 75 days or less. Popular varieties on the North Olympic Peninsula include Sungold (cherry-sized); Early Girl, Ispolin and Stupice (indeterminate); and Cosmonaut Volkov, Oregon Spring and Beaverlodge Slicer (determinate).
Plant tomatoes on a site that optimizes available heat
Tomatoes perform best when air temperatures are between 65-85 degrees during the day and above 55 degrees at night
To achieve these temperatures, plant your tomatoes in the sunniest and hottest part of the garden. A south-facing side of a building provides reflected heat and is an excellent spot for warmth-loving tomatoes. Furthermore, at night the building and its foundation will release heat absorbed during the day, thus keeping the plants warmer.
If you don’t have a sunny wall, look for a spot in full sun that is sheltered from the wind.
Consider planting your tomatoes in raised beds. Soil in raised beds is more exposed to the sun and wind and dries out quicker than ground level soil. Drier soil warms faster in the spring and will allow you to plant your tomatoes outdoors sooner.
Get a jump start on quick growth
Prepare your garden before planting; cultivate the soil as deeply as possible so the roots have no problem settling into their new home. If soil is heavy (that is has a high clay content) or low in organic matter, incorporate 2-3 inches of compost, aged manure or peat moss into the area to be planted and work it into the top 6 to 12 inches of soil.
Our short growing season and cool soil temperatures do not allow for direct-seeding of tomatoes in the garden. Buy transplants or start seeds indoors six to eight weeks before you expect to transplant them into the garden.
Do not plant your tomato plants outdoors until the danger of frost is well past and soil temperatures have warmed to about 60 degrees. This usually occurs in late May or early June on the North Olympic Peninsula. A few days before planting, warm the soil by covering it with clear plastic.
Be sure to harden off your tomato plants before planting them in the garden. Move the plants outside each day for an increasing number of hours and bring the plants indoors each night over a 7 to 10 day period.
When planting tomatoes, set plants deeper in the soil than they came in the pot. Roots will grow along the stem, providing a strong root system. Carefully remove any leaves along the stem that will be submerged below ground level.
Use covers or screens early in the season (and again as temperatures cool in late summer) to increase air temperatures around the plants and lengthen the growing season. Floating row cover, cloches, and low tunnels all work well to increase ambient temperatures. Because these covers can warm plants significantly under certain conditions, they will need to be removed or vented on sunny days to prevent plant damage.
Jeanette Stehr-Green and Audreen Williams are WSU-certified Clallam County Master Gardeners.