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How to Grow Seeds Indoors Part 2: Planting Method
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Timing Is Everything
Understanding the best time to start seeds indoors for a successful growing season.
Root vegetables (such as radishes, carrots, beets and turnips) need to be directly seeded into the garden, but I will try to get a head start on all the others by planting indoors to be transplanted outdoors later as seedlings. With indoor seed-starts, timing is everything. Start too soon and I’ll be babysitting lanky teenagers before it’s safe for them to be outdoors. Start too late, and they won’t have enough time to grow up. In my climate, I can start cool season crops indoors in late February. My warm-season plants can’t be transplanted outdoors until after Mother’s Day. Sad, but true.
The Old Farmer’s Almanac has an annual planting calendar by zip code that lists popular vegetables and suggests indoor seed start, transplant and outdoor direct seed planting dates.
Common cool-season vegetables: asparagus, beets, broccoli, Brussels sprouts, chives, cabbage, carrots, cauliflower, Swiss chard, kale, leek, lettuce, onion, parsnips, peas, radishes, spinach, and turnips.
Common warm-season vegetables: beans, corn, cucumbers, eggplant, melons, peppers, zucchini and summer squash, pumpkin and winter squash, sweet potato, tomato, and watermelon.
Pre-Sprouting for a Head Start
Using a simple method to test seed viability and speed up germination.
I pre-sprout some seeds with long germination dates by placing them in a folded, wet and wrung-out paper towel in a Ziploc bag, labeled with plant type and date. Since pre-sprouting takes less time than soil germination, I keep a close watch. As soon as I see a root starting to grow, I transfer the seeds into seed trays. (If seeds are past their recommended use date, pre-sprouting provides an easy test for viability.)
Planting and Caring for Seedlings
Seeds need oxygen, moisture, and warmth to germinate.
I pour light and fluffy seed-starting mix (not potting mix) into a dishpan and add enough water so that I can press the mix into a ball, but not so much that I can squeeze water out of the ball of mix. I fill the seed tray sections with soil. I press an indentation into the soil with my finger. The seed packets list recommended seed depths. (Lettuce seeds need light to germinate, so they stay very close to the surface.) I plant one pre-sprouted or three unsprouted seeds per cell, as not every seed will germinate. Finally, I sprinkle more seed-starting mix on top and gently press down to make sure the seed has good contact with the soil. I give the tray a quick spray of water and label the tray with the name of the seed and the date planted.
Nurturing and Transplanting with Care
Homemade starting mix recipe: 2 parts compost, 2 parts coconut coir, 1 part perlite.
I cover the seed trays with plastic wrap to keep them moist just until green shoots appear. I keep the seed trays indoors on a shelf in my laundry room as seeds germinate, checking the moisture daily. As soon as the green shoots appear, I move them to the garage under the lights. Plants need more warmth to germinate than to grow, so the seedlings will be fine in my unheated garage .
Once seedlings are under the lights 12-16 hours each day, uncovered, I keep the roots moist with 15-minute soaks two to three times a week. I want to keep the top surface of the soil dry to avoid the growth of moss and fungal diseases. I also use the fan several hours each day to gently stress the stems and leaves.
After true leaves appear, if more than one seed per cell has germinated, I remove all but one seedling per cell, leaving the largest seedling to grow alone. I use a small pair of scissors to snip the shoot at the soil level, rather than pulling it out. This will avoid the risk of damaging the roots of the surviving seedlings.
When the first set of true leaves appear, I move seedlings into individual, labeled paper drinking cups—small 3 oz. bathroom cups good for cool season starts like lettuce and spinach and 16 oz. drinking cups for tomatoes, peppers and squash. I try to be careful to handle the seedling with its leaves, not its stems or roots. I also dose them with half-strength liquid fertilizer.
I want to avoid multiple up-potting to minimize risk of damaging root systems, so I try to avoid the common mistake of starting seeds too soon. I bond with these babies and toddlers. I coo, cajole, scold and praise them. When they struggle, I worry. When they thrive, I celebrate. I blame myself for their failures and take pride in their successes.
Oh, the pain and joy of gardening!
