Growing Tomatoes in Alaska
Tomatoes might be the most beloved crop in the home garden, and for good reason. Nothing in the grocery store comes close to the flavor of a homegrown tomato picked at peak ripeness. Yet growing tomatoes, especially in northern climates like Alaska, is a different game altogether. It requires attention to detail, thoughtful planning, and a solid understanding of what tomatoes need to thrive in our cool climate.
Growing Tomatoes in Alaska
Where it All Began
Tomatoes have been part of human cultivation for a staggering 80,000 years, originally wild plants native to Western South America. Over time, they’ve developed into the 10,000+ named varieties we see today: from tiny cherry tomatoes to sprawling beefsteaks. They belong to the nightshade family, alongside peppers, potatoes, eggplant, and tomatillos, all of which share a common trait: the presence of naturally occurring compounds like solanine. While harmless in ripe tomato fruit, solanine is present throughout the leaves and stems of the plant, reminding us that tomatoes are wild at heart.
Taming a Wild Species
Growing great tomatoes always starts with location. Tomatoes are heat-loving plants that demand sunlight and warmth. In northern regions, that often means creating a microclimate specifically for them.
Choose the sunniest, driest, most protected spot in your landscape. Tomatoes require a minimum of six to eight hours of direct sunlight per day. Ideal temperatures hover around 75°F during the day and 55°F at night. That can be pretty challenging for most areas of Alaska- creativity is paramount in growing tomatoes here.
Beyond heat, air flow and bottom watering matter just as much. Tomatoes thrive in dry, well-ventilated spaces where air can move freely through the leaves. It shouldn’t feel windy, but the air should never feel stagnant either. This is why overhead watering is discouraged: wet leaves and poor air flow are an invitation for disease.
Growing Tomatoes in Alaska
Why Prune?
Pruning tomatoes is a practice that many gardeners shy away from, but it makes a world of difference, especially for indeterminate varieties (more on this in a bit). Pruning increases air flow, reduces splash back from watering, helps leaves dry faster, and minimizes the risk of soil-borne diseases. It also focuses the plant’s energy on fruit production rather than excessive leaf growth.
Use clean, sharp shears. Start pruning when your plant is about two feet tall by removing the lower leaves and any early flowers. Later, you’ll want to remove “suckers” which are those small shoots that emerge where the leaf stem meets the main stem. In those areas with a much longer growing season, suckers can be rooted to create plant clones.
About thirty days before your first expected frost (right before the fair) I “top” my tomato plants by cutting off the growing tip to redirect all remaining energy into ripening the last fruits. I also restrict water to assist in vine ripening.
Determinate vs. Indeterminate: Know the Difference
Tomatoes are divided by growth habit, and this distinction changes everything about how you manage them.
Determinate tomatoes are compact, bush-like plants, typically reaching three to four feet tall. They produce their fruit during a specific window and have a set number of fruit (determined amount of fruit production) before perishing.
Determinate tomatoes do not require pruning (with the exception of the first foot and they do well in cages).
Indeterminate tomatoes are the vining type growing anywhere from six to twenty feet long and will continue producing fruit until frost kills the plant (undetermined amount of fruit production). These tomatoes need sturdy support and benefit from regular pruning to direct their energy into producing fruit rather than foliage.
Watering: The Art of Consistency
Tomatoes don’t like surprises, especially when it comes to water. Inconsistent watering is one of the leading causes of fruit cracking and weakened plants which welcome both pests and disease.
Tomatoes need about one inch of water per week (a little more than half a gallon), delivered deeply and less frequently rather than shallow, daily sprinkles. Drip irrigation, timers, and even simple watering schedules written on a calendar can prevent common watering mistakes.
Containers, in particular, dry out faster than in-ground plants. A five-gallon minimum is recommended for each tomato plant grown in a container, with water applied every two to three days until it drains out the bottom.
Preventing Common Tomato Problems
Many tomato problems are environmental and preventable. Be sure your pruning equipment is clean and sanitized. I also suggest that pruning is done during the first part of your day when you too are clean and not contaminated by outdoor growing spaces.
Cracking comes from periods of drought followed by a sudden flush of water. Prevent this with consistent watering and mulching.
Blossom Drop happens when night temperatures stay above 70°F, or humidity is too high. Proper spacing, airflow, and reducing nitrogen inputs can help.
Blossom End Rot shows up as dark, mushy spots at the bottom of the fruit. Balanced soil, adequate calcium, and consistent moisture are key. I have found insufficient or improper pollination to be the main culprit of blossom end rot. Tomatoes are self pollinating, but the pollen may not flow freely at times preventing complete fertilization to occur.
Late Blight begins as brown to black spots on stems and leaves. Unlike some other diseases, the lesions aren’t contained by the leaf veins and can spread quickly. Phytophthora infestans thrives in cool, wet conditions and is spread by airborne spores or infected plant material. To control it, remove infected parts immediately, avoid overhead watering, practice crop rotation and ensure thorough garden cleanup.
Powdery Mildew appears as a white coating on leaves. Keep air moving, avoid overhead watering, and prune regularly.
Leaf Curl is usually a stress response; too much pruning, heat, or nitrogen can trigger it.
Nutrient Deficiencies show up in leaf color changes purple (phosphorus), brown edges (potassium), or pale yellow (nitrogen). The fix is always to start with a well-balanced soil and amend as needed.
Starting Tomatoes from Seed
Tomatoes should always be started indoors in northern climates. They love warmth, steady conditions, and good fertility from the very beginning.
Choose a dedicated space that stays between 65°F and 75°F. Use seed-starting trays or four-inch pots, and fill them with a sterile or balanced growing mix. Water deeply before planting, label everything clearly, and use a heat mat to maintain steady warmth for germination.
Plant tomato seeds about a quarter-inch deep. Most will germinate within seven to ten days if the temperature is right.
Once seedlings have true leaves, begin fertilizing with a diluted liquid amendment or compost tea. When it’s time to transplant outdoors, do so only after the soil has warmed and nighttime temperatures stay reliably above 50°F.
A Few of My Favorite Varieties
For northern gardeners, I lean heavily on heirloom/ open pollinated and indeterminate types for their flavor and resilience.
Black Cherry: small fruits with huge flavor.
Green Tiger: beautiful, striped fruit perfect for snacking.
Black Krim: rich, deep flavor with striking color.
Moskvitch: slicer that handles cooler weather well.
For those interested in saving tomato seeds, open pollinated varieties are a great start for beginners. Tomatoes for seed saving require an additional 6-8 weeks on a living vine to ensure maturity. Immature seeds or those seeds harvested in the juvenile stage may have impacts on the genetics of future generations (susceptibility to disease, loss of desirable traits, smaller fruits, poor fruit quality, weak seedlings, lack of vigor, reduced genetic stability, shorter storage life and decreased germination).
Final Tips
Interplant your tomatoes with herbs like dill and flowers like marigolds or alyssum. These plants help with pest management, pollination, and soil health.
Tomatoes are by far the heaviest feeders in the annual Alaska garden. They should have a fertility schedule of a feed every two to three weeks. Prior to the appearance of flowers, a well rounded fertilizer can be used to promote leaf and root development.
Once the plant is mature enough to reproduce, tomato plant fertility should be steered towards flower and fruit production. For the home gardener who is purchasing their fertility program, I recommend fertilizers that are OMRI certified (Organic Materials Review Institute) made from materials considered regenerative if possible.
Tomatoes can suffer tissue damage when temperatures fall below 45F. For those times, cover your plants with sheets or use thermal mass to increase the temperature by a few degrees.
Although a vine ripened tomato is surely the reward of summer, tomatoes can be harvested at a “blush” when just a hint of color appears. They can finish fully ripening indoors.
Lastly, we can’t forget about all the green tomato recipes out there- unripened tomatoes can be a treat in themselves.
In the north, we don’t grow tomatoes by accident. We grow them with intention, preparation, and a whole lot of patience.
About the Author:
Jennifer Sharrock is a regenerative seed grower, educator, and founder of Seeds and Soil Farm in Palmer. She grows Alaska adapted flower, vegetable and herb seeds in Southcentral Alaska. Follow the the Alaska Seed journey on Instagram @seedsandsoilfarm and learn more at seedsandsoilorganics.com