Growing vegetables and flowers from seeds instead of just buying nursery plants may seem like an exercise in delayed gratification, but it’s actually lack of patience that spurs most gardeners to sprout seeds indoors, ahead of the growing season.
Seed catalogs arrive, and folks get antsy. Starting seeds indoors allows them to put their green thumb to work several weeks before the last spring frost.
But starting too soon is one of the main reasons for failure because the plants only thrive for so long indoors, says Mary Ann Gowdy, a plant sciences professor at the University of Missouri. “It’s hard,” she admits, “but you have to resist the temptation to start too early or you’ll end up with wimpy plants.”
Insufficient lighting is another common mistake. “People don’t realize how poor their lighting is indoors,” Gowdy says. “Seedlings need a lot of light and seek it out, stretching really tall if there’s not enough so you end up with weak, thin stems that are kind of floppy.”
Seed-starting success starts by looking up the sowing schedule for your USDA plant hardiness zone, searchable online by ZIP code. Here in southeast Minnesota, we are in zone 4b. The backs of seed packets have germination schedules so you can figure out how far in advance to plant. Most vegetables can be started four to six weeks before it is safe to move them outdoors, Gowdy says.
Tomatoes, carrots, bell peppers, lettuce and sugar snap peas offer a high rate of success and are best for beginners and children, says Rebecca P. Cohen, author of “Fifteen Minutes Outside: 365 Ways to Get Out of the House and Connect with Your Kids.”
Annual flowers including marigolds and morning glories tend to succeed as well.
Experienced gardeners “like to start on their own because they can get all sorts of plant varieties that aren’t available at garden centers including heirloom varieties,” Gowdy says.
Seedlings grow best in a sunny, south- or southwest-facing windowsill. Plant them in a special seed-starting mix, not potting soil or dirt from outside. Moistening the mix before planting helps prevent seed displacement. Seed packets generally tell you how deep to plant.
Garden centers sell biodegradable grow pots and seed-starting trays offering a “bottom-up” water supply so as not to disturb delicate seedlings; however, “You can grow plants in just about anything as long as you add drainage holes,” Gowdy says.
Small seeds, such as lettuce, can be planted in cardboard egg cartons, and since the material absorbs excess water there’s no need for drainage holes, Cohen says.
Plant bigger seeds in pots made from toilet paper rolls. Use scissors to cut quarter-inch strips all around one end of the tube, and then fold the strips down so they overlap to form the bottom of the pot.
Sow one seed per roll, or two to three to up your chances for success. “If all the shoots come out, only keep the strongest one,” says Kathleen Brenzel, editor of “Sunset Western Garden Book of Landscaping.”
If kids are involved, have them moisten the soilless mix in homemade containers by squeezing a wet cotton ball, or water from the bottom in a tray designed for that purpose. “It prevents them from overwatering,” Cohen says.
Since adults tend to overwater, too, “Mr. Brown Thumb” garden blogger Ramon Gonzalez recommends punching holes in the top of a water bottle with a sewing needle – “as many small holes as you can fit on the lid for a gentler stream of water.”
Seedlings started in smaller pots need to be transplanted to larger pots as they grow, but peat-pot or toilet paper roll “collars” can be left in place as they’ll biodegrade over time. Generally, the bigger plants get, the greater their daily sunlight and water requirements.
A week or two before transplanting seedlings to the garden, “harden them off” – or help them acclimate – by taking them outdoors for increasing lengths of time on mild days. But don’t withhold your TLC. When you finally transplant the seedlings to the ground, be careful with the roots, and provide supportive stakes or cages for tomatoes and other climbers as needed.