When you’ve got latitude/altitude working against you, there’s a shorter growing season to contend with. I think tomatoes are very doable in short-season climates… However, they require some help. They normally do very well with lots of heat units (the average number of degrees above freezing every 24 hour period) through the summer… especially late in the season as they start ripening up. Just as your plants start really going nuts, you run out of growing season.
My best advice? Make a Mini-greenhouse out of 2 X 2 pieces of lumber and clear plastic stapled over it in double or triple layers. Make it at least 4 ft wide, by 4-5 ft long (LONGER IF YOU WANT TO COVER 2 AT A TIME), by 4-6 ft high. I usually wait until 8 weeks before our last average freeze date (mid-May here) and so that puts me at next week for starting my indoor tomatoes and peppers.
Depending on what you start them in, use small pots to begin. 2” peat pots are great, but don’t over water or get the little plants wet while watering. Put them in a tray and pour water in the tray, they’ll soak it up from below. Let them JUST BARELY dry out each time before watering again. “Damping off” is a common fungal disease for tomatoes and it proliferates with excess moisture and warmth. Once the roots start poking through the small peat pots, plant the best 4-6 (that many plants should be MORE than enough for a family) in 1 gallon plastic pots and grow them larger. Keep watering by filling a tray and letting them soak it up 2-3 times a week. DON’T overwater… they don’t like soggy roots at any stage of development! Be sure they get plenty of light and that you’re turning them around each day to keep them from leaning too much. They might get leggy, but that’s okay for this method.
Once you’re within sight of the last average spring freeze for your area (check with the local extension agent to find that out for sure!) get a couple of old used tires for each plant you want to put out. Put one tire on the ground, pull the tomato out of your plastic pot, and just set it on the ground. You don’t even have to dig a hole. Shovel a mixture of about 1/4 horse manure mixed with 3/4 garden soil around your tomato and water it thoroughly. The soil should settle quite a bit, but add more until the entire root ball of your tomato is covered.
Let it grow under your mini-greenhouse each night, only taking it off if the daytime high temp. gets above 50 degrees. Otherwise, just let it keep your little plant warmer than the surrounding air. The dirt and the tire build up heat units inside. If you get full sun and it gets warm, you might literally cook it, so it’s important to let it get some air at least every other day. Watch closely until you can be certain it won’t freeze at night anymore. The black tire will absorb a LOT of heat each day and hold it longer into each night as the temp drops.
When your tomato is about 12-15″ tall, snip or tear off all the lowest leaves and put a second tire on top of the first one. Fill it with the dirt/horse manure mix and water it down just like before. Keep adding more until you’ve got the entire two tires filled with dirt up to the top. You should have just a little bit of tomato plant showing above the top of your soil. None of the leaves should be buried! The plant will throw out new roots all along the portion of stem you buried with the second tire and you’ll get a VERY sturdy plant with lots of roots to start growing like crazy within a week or two.
You can use liquid fertilizer at 1/4 strength each time you water, but a sprinkling of slow release fertilizer on top will do about the same thing.
It usually takes tomatoes about 6 weeks or more to really start bearing and so you’re looking at mid-July or August before you can expect it to be doing much. The plants will likely be 3-5 ft tall by this time, perhaps needing support, but I let them just drape over the tires because the extra heat from the black helps them ripen (the lazy man’s way!). Each day the temperature is warm, you should take the mini-greenhouse off. Since tomatoes are wind pollinated, they need some breeze in order to set fruit (a blow dryer or leaf blower work great for this too!). Cover them each night if there’s even a whisper of it getting chilly (under 40 degrees) and get more and more careful as August comes to an end. You could get a freeze at any time then!
Once it starts freezing, your days are numbered… but your plants should be covered with green tomatoes if they are thriving properly. Fear not, green tomatoes are still tomatoes and when you finally get a hard enough freeze to really kill your plants back, just yank the entire plants and hang them in the basement rafters (where it’s cool and has higher humidity than most of your house) or you can wrap each green tomato in newspaper and sit them along all your window sills. Believe it or not, nearly all of them will ripen this way and you’ll be enjoying fresh, home-grown tomatoes well into December and January if you’re careful. You can preserve them by canning, making chutney, salsa, tomato juice, sauce, etc. for even longer enjoyment of your harvest. Check out the article on using green tomatoes for some great recipes. I adore the green and red tomato casserole pie!