Getting a jump on the growing season up here is the secret to a successful garden in Alaska. That means starting seeds indoors while there is still snow on the ground. It is always foolish to expect any mild spring weather to last without some freezing nights. So you stick with your normal planting schedule and keep your seedlings indoors, or inside a heated greenhouse, until all dangers of a killing frost are over. We can have some sunny warm days, but night time lows can vary from the 20's to mid 30's until late May.
I use very common large commercial shelf units for starting seeds indoors under grow lights. I have a section of my living room set up for growing plants including a potting bench. You can find these common shelves at most home centers, Costco, or online.
These unites come in many sizes to fit your available space from 36 to 48 inches wide and 40 - 72 inches tall. My shelf racks are 48" wide by 18" deep and 72” tall and came with 5 shelves that I can customize to my preference. This size will hold two 10X20 seed flats end to end per shelf and I use a 4 bulb grow light for each shelf. I recently went to a larger shelf unit that is 24” deep and allows four 10X20 seed flats so fit side by side instead of just two end to end and will hold twice as many flats per shelf. This required more light so I replaced some of my 4 bulb lights with 6 bulb grow lights. I also recommend wheels for moving and shelf liners to keep dirt and water spills from falling through.
The light system I have been using was a 4 bulb T8 Florescent Shop light. I have since replaced the Florescent bulbs with LED bulbs to save on power. I use all LED Grow lights now. I control my lights with a simple timer switch and set my lighting cycle for 16 hours.
I start my tomatoes around early February. I only grow Bush Early Girl Hybrid tomatoes that have larger fruit and are very resistant to disease and do not haver a cracking problem like Extreme Bush Tomato that I was growing. I prefer a more compact bush tomato variety as they do not grow too tall inside my greenhouse.
I have been very happy with my Parks Seed Company 40 cell Bio-Dome seedling trays that use foam grow plugs. This is a tray of seedlings in my Bio-Dome that look very healthy and almost ready to transplant.
I have had very good results with these trays and almost 100% germination. I will plant 2-3 seeds in each cell and then trim off any extra seedlings leaving just one plant per cell.
In about 2-3 weeks I will transplant my healthy seedlings into 3 1/2 inch pots.
My tomatoes are usually then transplanted again into half gallon pots in April.
It can get crowded in my indoor garden waiting for warm weather before moving plants out to my greenhouse in May. Many years I seem to run out of room. It is necessary to heat my greenhouse at night during May and keeping track of the overnight low temperatures with my home weather station is very important.