Starting seeds indoors turns out to be a necessary skill if you want success with early crops that prefer cooler temperatures during the growing season like cabbage, broccoli and Brussels sprouts.
Setting out a young plant means it has a chance to reach maturity before our summer temperatures soar and the plants bolt and become bitter.
The tools for starting seeds indoors can come assembled like a domed kit or you can craft your own using shallow containers (or a shallow flat with drainage holes, like you would get if you bought a flat of pansies), a sterile growing medium like a 50-50 mix of vermiculite and peat moss, some clear plastic, and a spray bottle.
For the second phase, you’ll need some small containers and potting soil when the seedlings are ready for their first transplant.
I typically use small containers left over from store-bought plants.
Moisten your germinating mix in a bucket before filling your flat; then take a pencil and make several shallow furrows in the mix; drop your seeds in (check planting depth on the seed packet, some seeds need light to germinate so you do not want to cover them with your germinating mixture); gently moisten again with your spray bottle and cover with a plastic hood or homemade tent (if you prefer the homemade version use pop sickle sticks to support your tent). Plug in your heated mat if included.
The plastic covering increases the relative humidity and moderates the soil moisture as the seeds germinate.
Open the tent daily to see if more moisture is needed, mist accordingly using your spray bottle. Consistency is necessary for both moisture and warmth.
Seeds need varying degrees of warmth to germinate so for cool season crops you may not need any more heat than what a sunny window or some grow lights will provide. Summer crops will benefit from an additional source like a heating mat.
You don’t want to cook your seeds, just keep them on the warm side.
It is not ideal to put them by a heat register or refrigerator because this is an inconsistent source of warmth and dries the seedlings out.
If your tray is in a bright window you will need to rotate the tray daily once the seedling emerge; grow lights overhead are ideal because the seedlings grow stout and straight.
Once your seedlings emerge, remove the covering and begin to water the tray from the bottom to maintain even moisture (not soggy).
Once the second set of true leaves form (those that are the shape that you associate with the plant), your adolescent seedlings are ready to be transplanted into their own pot containing transplant mix; return them to their light source (if they are in a window give them a quarter turn every day so they grow straight).
Continue to water your transplants from the bottom when needed, adding some diluted fish emulsion fertilizer once a week.
When conditions are right for your particular plant (check the seed package for details) acclimate them to the outdoors before planting them in the garden.
Put them outside in the shade, first, gradually moving them into the sunlight; they will be ready to plant in the garden in about a week.