My orders for onion sets and seed potatoes will arrive next week and will be planted once the soil dries a bit; my favorite summer crops that will be directly seeded in the garden are still in their seed packets waiting for consistently warm weather before they find purchase in the soil. I can barely stand the wait. So, to ease the tension, I will fill a few seed trays of early season vegetables that like a cool start to the season. Kale, broccoli, cauliflower, and Brussels sprouts are just beginning to push through the light potting mix.
My set up is not elaborate; it basically consists of a kit that includes a plastic dome that fits over a seed tray and pan. The kit came with a heated mat which helps to deliver some bottom heat to the tray and expedite the germination of certain crops that really like it warm like tomatoes, peppers, and eggplant. You don’t need a kit, however, 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), fill the flat with sterile growing medium like a 50-50 mix of vermiculite and peat moss, and then top it off with some clear plastic. Of course, you need to plant some seed at some point.
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, germination really does benefit from some bottom warmth. 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 the air movement dries the seedlings out. If your tray is in a bright window you will need to rotate the tray daily once the seedlings 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; you can use small pots left over from store-bought plants. Once they are transplanted 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; and when conditions are right for your plants (check the seed package for details) acclimate them to the outdoors before planting 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.
