Tomatoes for Cool Climates

Tender, heat-loving tomatoes (Solanum lycopersicum) perform best in climates with a long, warm growing season, but that is not to say that you can't grow them if you live in a cool climate. Choosing the right type of tomato makes all the difference, and many different cold-tolerant varieties exist, whether you prefer the old-fashioned heirlooms or newer hybrids.

Tomatoes need nighttime temperatures to stay reliably above 55 degrees Fahrenheit, and preferably above 60 F. Temperatures below 50 F inhibit growth, which often proves problematic in short-season areas with low spring and fall temperatures. When choosing a cold climate tomato look for:

Early bearing varieties: Ideally, choose a type that produces ripe fruit in under 75 days. Remember that tomatoes grown in cooler climates can take an extra 10 or so days to ripen, so choose accordingly.

Determinate types: Bushy, compact determinate tomatoes often mature faster than indeterminate varieties, but that is not always the case.

Hybrid varieties often prove more cold-hardy and disease-resistant than heirlooms, but there are several notable exceptions.

Heirloom, or open-pollinated, tomatoes are older types bred by hand. Fewer cold-tolerant heirlooms exist than hybrids, and they are generally more delicate and less resistant to disease. You can still choose from handful of hardy, prolific heirlooms that were bred in cold climates and fare well at lower temperatures.

Large, round heirloom tomatoes with suitable cold tolerance are relatively rare because larger fruit typically takes longer to ripen. One exception is 'San Francisco Fog' (Solanum lycopersicum ‘San Francisco Fog’), a prolific type that produces clusters of 2- to 3-inch fruit in 70 days. It bears well in cool, wet climates where other varieties often fail to thrive.

A hardy and early variety of tomato is the ‘Stupice' (Solanum lycopersicum ‘Stupice’), which is of Czech origin. It produces flavorful, 2- to 3-inch fruit in 52 days. The ‘Black Prince’ (Solanum lycopersicum ‘Black Prince’), a Siberian variety noted for its dark flesh, was bred in the Irkutsk region of Russia. Its fruit ripens in 70 to 90 days, and it has been known to produce 25 to 40 pounds of fruit over the course of three months.

'Stupice' is pronounced "stoo-PEECH-ka."

The greatest diversity of cold-tolerant types comes from the realm of hybrid tomatoes. From large-fruited varieties to the smallest cherry tomatoes, hybrids can meet your needs in terms of variety.

One of the earliest types of tomatoes is the ‘Siletz’ (Solanum lycopersicum ‘Siletz’), which ripens in roughly 57 days. It is noted for its flavorful, nearly seedless flesh and dark red color. ‘Early Goliath’ (Solanum lycopersicum ‘Early Goliath’) ripens in 60 days. It is among the largest early-bearing tomatoes known for its deep, dark flesh.

A dependable ripener, the ‘Willamette’ tomato (Solanum lycopersicum ‘Willamette’) is ready for harvest in around 70 days. Its red, firm flesh has a mild flavor, much like ‘New Girl’ (Solanum lycopersicum ‘New Girl’), an early bearing variety that matures in 58 to 65 days.

Plum, cherry and grape tomatoes are all small-fruited tomatoes. Dozens of small, early-bearing hybrids exist, including common varieties such as ‘Super Sweet 100’ cherry tomato (Solanum lycopersicum ‘Super Sweet 100’). The sugary, 1-inch fruit ripens after 65 days and will continue to produce fruit until the first frost.

Super hardy varieties such as ‘SubArctic Maxi’ (Solanum lycopersicum ‘SubArctic Maxi’) thrive at high elevations and will bear small, red-fleshed fruit in just 48 days. It barely crosses the finish line before ‘Fourth of July’ (Solanum lycopersicum ‘Fourth of July’), which matures after 49 days. The juicy, firm fruit forms in clusters of six to eight, and each is large enough to slice.

Tomatoes are tender, warm-season vegetables that resent the cold even if they tolerate it. Temperatures between 55 and 85 F are best, but raising soil temperatures early in the season in cooler climates often proves difficult. To hasten warming, try:

Full sun exposure: Growing with full, unshaded southern or western exposure provides the most consistent warmth.

Plastic mulch: Covering the bed with plastic sheeting can raise soil temperatures by 6 F in the top 2 inches.

Growing in pots or raised beds: Both encourage soil warming and can be arranged in naturally warmer areas, such as against south- or west-facing walls. Just be sure to use a pot with plenty of drainage holes.

Tomatoes must be started indoors roughly six to eight weeks before the last frost. Don't start them too early.