BY ERIK LARUSSON | Special to Moonshine Ink
By mid-winter, we gardeners begin to crave getting our hands into soil. Starting seeds indoors seems a daunting task and some are hesitant to try. But it is as natural as seeds sprouting from soil, it is inexpensive, and it is immensely satisfying. The stakes are low; what have you got to lose but a few seeds?
The following are tips I’ve found work best in our unique climate. For the sake of brevity in this missive … background and reasons are omitted. You’ll have to take my word for it.
Timing: When to plant seeds indoors in Truckee/Tahoe depends on the plants you are growing and where you’ll be growing them. Seed packets tell you to start indoors ‘X’ days before the “average last date of frost.” (= a < 50% chance of a < 32ºF night). Location dependent, our “date” may be some time in June (earlier for higher slopes / later for lower flats). In part because of our elevation and low relative humidity our daily temperature swings can be tremendous. Local seeding times are based on experience and on our ability to protect young plants (if tender) from frost when they are put outside (i.e. greenhouses get a big head-start).
Essentials for seeding successes
Good seed: According to USDA maps, we are in zone 6. If you want to choose plants that will actually survive here, use zones 3-4. Use fresh seeds that are less than 3 years old. Choose seeds for cool climates and short seasons. Hardware and drug stores have premixed regional seed racks, while experienced local nurseries select each and every variety of seed they offer, specific to this climate.
Seed-starting mix: Always use a seed-starting medium with ideal moisture-holding, aeration, and drainage. Never use earth, compost or old potting soil as you’ll introduce pathogens and ruin the structure.
Seed Starting Tray: I use 10-inch by 20-inch seedling trays with starter cubes, or pots or plastic with peat or coir (fiber of the husk of the coconut fruit) cell-packs in them. The tray keeps water from going all over the floor and it holds moisture. Many people prefer to water tender seedlings by adding a little water to the tray and letting the moisture wick up into the containers.
Moisture: Fill containers with starter mix and water thoroughly, several times. Once seeds are planted, they can never dry out and they should never have more than a quarter- to half-inch of water in the bottom of the tray. Most trays have clear lids that should be used before seeds germinate and while seedlings are very small. Covering the tray with a secured clear plastic bag or plastic-wrap also works. Lift the lid at least once a day to refresh the air.
Proper Planting: Many seeds have specific depths at which they need to be planted, noted on packets. Generally, larger seeds require deeper planting. Water new seeds initially and occasionally with a half-strength seaweed extract. It has natural plant hormones that stimulate root growth, strengthen cell walls, and help prevent disease. Take care not to over-seed, expecting you can thin later. Two to three seedlings per pot allows for a healthier growing environment and leaves the remaining seedling less damaged by thinning.
Location: Many seeds prefer dark for germination, so I sprout the seeds above the refrigerator and then move them. Windowsills are the most common location for seedling trays, but they can be too cold at night and the light can be too intense. The ideal window is east facing. I put many of my seeds on racks near windows with supplemental light and bottom-heat.
Bottom heat: Heat mats are long-lasting, reusable flat heaters that sit beneath seedling trays. Bottom-heat speeds germination in all but a few plants. Cruciferous vegetables (Brassica species including broccoli, kale, and mustard) do not need bottom heat. Rapid germination reduces chances of seed rot and pathogen attacks. Heat mats should be turned off once seedlings are producing leaves.
Supplemental Light: My go-to for seedling lighting have been inexpensive 4-foot fluorescent shop lights from T12s to T5s, and now LEDs. Incandescent lamps are too hot and inefficient. When seedlings are fully emerged, they will benefit from supplemental lights. Remove the lid and make sure that the plants don’t dry out. Shop lights should be kept just 3 to 4 inches above the growing plants. Increase light times from four to 18 hours over the first few days to accustom the seedlings to the light. For plants with good window light, use supplemental light only at night. Plants should be turned every day so the seedlings don’t bend one way. An oscillating fan used for 30 minutes, twice daily, reduces disease and strengthens seedlings.
~ Eric Larusson has degrees in molecular biology and in horticulture and learns more every week. He has worked primarily with Villager Nursery since 1984.