I've had a couple of questions about starting seeds indoors. I'm happy to share what's been working for me.
You'll need to keep in mind that I'm fairly new at this; my habit until last year was to simply sow all seeds in place, except for tomatoes and peppers, which I would buy as seedlings from the Master Gardeners. Only last winter did I decide to start my own indoors, and I bought a very simple, one-tray system with grow light and heating mat. The seed tray had 55 cells, which was just enough for two each of 16 tomatoes, and both sweet and hot peppers.
I've scaled up my operation quite a bit this year, having decided that it might be better to start everything from seed except those plants that prefer to be sown in place. My little one-tray system wasn't going to cut it. Also, that tray was designed for peat plugs, and the more I read about the doubtful sustainability of peat, the less I want to use it.
So, here are the items I budgeted for and purchased (and also those Tom and my dad created by hand) for seed starting this year.
1) Fresh seed. In the past couple of years I've been relying on a source of free seeds for all my vegetables - there is a gentleman in my neighborhood whose mother is a master gardener and has a nonprofit community plot. She always has extra seed, so she sends it to my neighbor, who very generously gives it out, once or twice a year. I looked at this as a great way to save some cash. The problem is, the packets are always at least two years old. And while a lot of seed can live that long, it's usually only under perfect conditions. Who knows where this seed was kept in the intervening two years? It could have been kept in a hot and muggy garage, for all I know. I figured that I needed to increase my germination success by starting with fresh seed, collected last year and dated for this one. Even then, germination is rarely 100%.
2) A new, larger table in a larger space in our living room. I had used a small side table in my bedroom last year; this year I went into my dad's furniture storage, where he keeps furniture that he has made but that no longer fits in his home. I found a solid cherry table, made in 1983, that I remember using as a computer table when I was a teenager. It's the perfect size for a corner in our living room. Our 1949 cottage is only around 1000 square feet, so making room for this table was no easy thing. It speaks to how committed we are to a bountiful harvest that we managed it. Not to mention that it's right in the center of our home. It's a good thing we don't entertain often.
3) New trays and seed starting mix. I decided to buy 5 72-celled trays and 5 drip trays to go underneath them. I figured that was enough room for any number of seedlings, some in early production, and some moving in to the greenhouse (another thing we had to build and you can see how we did that in one of our videos). I bought bags of new seed starting mix as well (though most seed-starting mixes do include some peat).
4) New lights and heating mats. The lights are important, mimicking the sun. You want bulbs that are 5000 Kelvin and 800 Lumens (they will be labeled 'daylight,' but also check these numbers). The bulbs are the most expensive part of this whole process. If you buy LED, they should last your lifetime. I also had to buy light fixtures to put them in, so I got clamp lights. The heating mats are sized to fit under standard seed trays.
5) New lighting rig. Because we decided to go with clamp lights and bulbs, Tom had to rig up a system to hang them over the trays. He built a sort of cage, which is very sturdy, and we are hanging the lights from the cage using bits of rope. That way I can tie them at the heights I need them - lower when the seeds are just germinating, higher when the plants begin to grow, and I can also move them around. We needed several power strips to house all the plugs. By the way, many people leave their grow lights on 24 hours a day, but we do not - our house is so small, the lights would keep us awake. We just turn them on first thing in the morning and turn them off before we go to bed. This has not been a problem in the past.
A couple of other things I bought: 1) a spray bottle to use in watering the seeds - I do moisten the planting mix before packing it into the cells, but then afterward I lightly spray the surface once a day, maybe less if they look ok; 2) good old-fashioned popsicle sticks to label my seed cells; and 3) a waterproof tablecloth to lay on dad's table and protect it from water and heat.
So far, I'm happy with this system, but at the moment I only have a small amount of seedlings growing - 12 each of broccoli, cabbage, and cauliflower. When I reach full production at the beginning of March, I will know if this system works well. I imagine there will be some tweaking in our future.
A couple of caveats: Starting seeds in a sunny southern window seems like an easy solution, but the seedlings, if they germinate at all, will become quite leggy, reaching for the sun. They need a strong light source close to them in order to become stocky, healthy plants. Some seedlings should be fine with no heating mat (absolutely not the heat-lovers like tomatoes, peppers, and eggplant); ostensibly, the brassicas and greens you would think would do fine. It's worth a try. But I did find a really helpful chart at Fedco Seed (go here and look under vegetable planting chart), which tells you the temperature at which all seeds germinate. Broccoli prefers 65-85 degrees soil temp, and these heat mats provide that consistently.
I hope this helps you on your seed-starting journey; I know many of you are more experienced than I am, so please comment if you have ideas or suggestions. Happy planting!