A well-outfitted seed-starting station.
The reason to sow seeds ourselves is to take control. We might want a say in where a plant spends its summer. We might be afraid that over the course of a season we’ve gardened the seeds right out of the soil. Or we might want the reassurance of having extras to tuck in and give away. Sometimes I just want to try something new. And for those of us who lack confidence, it must be admitted that successful germination is one of those little thrills worth sowing for.
Seeds are designed to take advantage of whatever conditions will guarantee germination and survival. They read light levels, soil and air temperatures, and soil pH. They are ready to germinate only when the time and place read right, which explains why some plants behave like weeds in our gardens and others come up few and far between. We can be absolutely certain that embryos need moisture in order to germinate. Another rule of thumb (whatever color you consider yours to be) is that seeds should be sown as deep as they are long. You can sprinkle really tiny seeds right on the surface because the likelihood is they need light, as well as moisture, to germinate.
Last year’s stinking hellebore (Helleborus foetidus) seeds germinate alongside this season’s flowers in early spring.
It gets slightly more complicated when seeds are covered in a tough coat. Those seeds may be programed to wait out a dry season, germinating only after a soaking rain; they might need to be tumbled through the gut of an animal; or they might need a cycle of freezes and thaws to soften the coat. Whichever way they work, and sometimes we have to guess, gardeners can help trigger germination by scarifying or stratifying seeds before sowing.
Scarification
Seeds from self-sowers that are native to warm zones with dry winters may need to be scarified before they’ll germinate. Scarification is the process of opening a hard seed coat just enough to allow moisture in and enable the embryo to push through. You can scarify seeds by scratching the seed coat with a rasp, file, or sandpaper; nicking it with snips; or soaking it in warm water for a day until the coat softens. Be a scientist and experiment to find which method works best for your seeds. Sow scarified seeds directly in the spring garden after the last frost, or inside in dampened seed starter potting mix (more about that in “Indoor seed sowing”)—either way, be sure to keep seeds moist through germination.
Stratification
Seeds from self-sowers that are native to areas with cold, snowy winters usually need to be chilled before they’ll germinate. Stratification is the process of breaking dormancy by exposing seeds to moisture and wintery temperatures. Gardeners can experiment with a variety of methods, using either fake or real winter conditions.
Into the fridge or out to the shed
To stratify using your refrigerator, sandwich seeds between the folds of a damp paper towel, or within a handful of moist (not soggy) vermiculite, sand, or finely sifted potting mix. Place them in a resealable plastic bag in the vegetable drawer for at least a month. To really fake them out, take the seeds out of the fridge for a week at two-week intervals, to simulate freeze and thaw cycles. Or, place prepared seeds in a shed, bulkhead, or an unheated garage to go through the winter’s actual temperature fluctuations.
Seeds tacked up in the shed over the winter for stratification
Check on your seeds often to make sure the medium doesn’t dry out, the seeds don’t rot, and critters don’t eat them. Gently pot them up when the seed coat has released a tiny sprout, or after a few weeks have passed even if you haven’t yet seen signs of growth. If space allows, sow seeds in packs or pots instead, covered in plastic, before placing them in the cold fridge or shed. This will save you the anxiety of handling delicate sprouts after germination.
The snowmelt method
Some seeds need to be “washed” by snowmelt and any others that require winter’s chill probably won’t mind. If it snows in your neck of the woods you can sow seeds in a fine-textured, sterile, soilless potting mix in clean plastic pots, juice jugs, or salad boxes anytime over the winter. (The containers should be at least 2 inches deep with holes in the bottom for drainage.) Spread a thin layer of quartz pool filter sand over the top of the soil; this type of grit lets light in for the seeds that need light to germinate and holds them in place during watering. It also keeps moss from growing on moist seed starter, which is a problem especially when seeds take weeks, months, or even a year to emerge. Seed packets usually indicate how long you can expect to wait—try not to worry but recognize when to give up.
Place the containers outside and cover them securely with window screen, which will keep the wildlife out and let the snowmelt through. Protect the containers during heavy rain by bringing them inside or placing them under an overhang or garden chair. But also make sure they don’t dry out.
Direct sowing
Seeds that are sown directly into the garden in fall or early spring will germinate when the time is right, no worries. Highlight the area with a thin layer of grit or sand and a label to prevent inadvertently weeding seedlings out in spring. It’s also a good idea to create a blank blueprint of your garden so you can print out a new copy every year to map where you’ve sown what.
Seeds sown in containers being washed by snowmelt.
Lupine seedlings germinated in April.
TIPS FOR MANAGING VOLUNTEERS AND DIRECT-SOWN SEEDLINGS
Exercise restraint. Check for signs of life around last year’s patches of volunteers and your markers of winter sowings (consult your garden map if you made one). If you can’t identify seedlings, wait. Give them time for their true leaves to look familiar, and if you still can’t solve the mystery, wait for flowers. Likewise, if nothing has come up where you think something should, wait. The soil warms as the nights warm and some of the best self-sowers won’t be triggered to germinate until early summer. Or later. If you can’t wait, plant something else and cross your fingers for an interesting combination if and when survivors finally emerge.
Be your garden’s best judge. I’ve been known to let weeds grow—just in case they might be something special—until they flower and I finally realize in a panic what they are. I don’t stay embarrassed for long. Just remember, if ever you do not like the look of a plant as it grows then it probably isn’t meant for your garden when it blooms either. And if you do like the look of a mystery plant, then it probably isn’t a weed and unless it’s actually invasive, don’t let anyone tell you otherwise.
When necessary, commit to thin. Seedlings that come up thickly in the garden may be employed as a weed barrier at least until they start to look overcrowded. Then they should be thinned. Pull most out all at once or pull some out week by week until a precious few have the space they’ll need to grow to maturity.
Get to know your seedlings. Take pictures of your most wanted self-sowers as well as your most unwanted weed seedlings as they emerge. Make a gallery to jog your own memory and put them on display for family and friends who like to help out in the garden.
Thinning self-sown love-in-a-mist (Nigella damascena) seedlings.
Another option is to broadcast seeds on top of the snow. This is more than just a cathartic act of optimism in the middle of winter: you can rest assured that your seeds will get any stratification and rinsing they might need as the snow melts and settles them into the soil. Tiny seeds—such as poppies, sweet alyssum (Lobularia maritima), love-in-a-mist (Nigella damascena), and larkspur (Consolida ajacis)—work best because they are more likely to need light to germinate once they find their way to the soil. Take care you aim well over a patch of garden, not the lawn, and expect some shifting. Use a saltshaker to distribute seeds when mittens make it difficult to cup seeds or grasp packets.
Indoor seed sowing
Get a jump on spring by starting your seeds—whether new or saved, scarified or stratified—indoors. They’ll be ready to transplant outside after they’ve grown big enough to handle and the weather has warmed, and will usually come into bloom weeks ahead of those directly sown outdoors. Check the Farmer’s Almanac for your average last frost date and mark your calendar. Most seed packets will indicate exactly how many weeks ahead to start seeds before it’s safe to plant outside. When in doubt, start seeds six to eight weeks before your average last frost.
Sow seeds in clean plastic, clay, or fiber containers in a sterile soilless seed starter or finely textured potting mix. Spread a ⅛-to ¼-inch layer of quartz pool filter sand or chicken grit on the surface. In addition to letting in light, holding seeds in place, and hindering growth of moss, this keeps the seedlings’ point of contact with the soil from being overly wet which helps prevent damping off (a common indoor seed starting fungal problem).
Water the seeds in using a watering wand or a watering can fitted with a rose that allows the water to fall gently through tiny holes, or by setting the containers in a dish of water just until the soil is evenly saturated. The latter method prevents washouts, keeps the seeds from shifting all to one side, and won’t compact fine soil. Cover the containers with clear plastic to keep the soil from drying out before seeds germinate.
The biggest challenge to starting seeds indoors is providing adequate space, heat, air circulation, and light. To tease seeds into thinking it’s spring, the soil they’re sown in will have to be kept warm (about 70 degrees F) and moist until they hatch. The top of the refrigerator happens to be close to the ideal temperature but the lack of sufficient room up there is a drawback. So if you want to sow a lot of seeds, consider buying a heating mat, available in the spring from most hardware stores and garden centers. Regardless of location, watering with lukewarm water will also help to gently raise the soil temperature.
After germination
When the first leaves—the cotyledons—emerge, do a little dance and turn off the heat. Seedlings will grow sturdy and strong in temperatures ranging from the mid-50s F at night to the high 60s during the day. At this point seedlings also need a lot of light to keep from stretching and becoming spindly weaklings. One can only have so much south-facing windowsill space, and if yours is like mine, that sunbeam is already occupied by two cats and a dog. You’re golden if you happen to have access to a greenhouse. Otherwise, hang full-spectrum fluorescent lights a few inches above the seedling tray and set the timer for sixteen to eighteen hours of light per day. Be sure to keep seedlings from drying out, but never let them sit in water once the soil is moistened through.
Mark directly sown seeds with a wooden tag written in pencil (which doesn’t fade) and a sprinkling of sand.
The plant’s true leaves—you’ll recognize these as tiny versions of the mature plant’s leaves—will form above or alongside the cotyledons. At this point, you should begin feeding the seedlings once a week with water-soluble fertilizer diluted to half strength (there’s nothing nutritious in that soilless potting mix). To prevent the air around the seedlings from stagnating, keep a fan rotating nearby at a low setting.
After true leaves have formed is also the time to transplant seedlings that were sown thickly in packs or pots. Seeing seeds germinate is such a thrill that some of us may find it difficult to thin them out. But it must be done. Seeds sown thickly will compete with each other for space and nutrients and it would be tragic if none of those miracles thrived. Better to choose a few seedlings to grow on and chuck the rest.
Fill fresh pots with dampened potting mix and tamp it down to prevent air holes and settling. Use a salad fork to scoop selected seedlings from their pot and gently tease roots apart from each other. Always handle the seedlings gently by their leaves rather than their delicate stems. Then poke a root-sized hole with your finger and drop the seedling in right up to the first set of leaves (leggy stems will form roots to that point, providing a sturdier anchor) and tuck it in. Transplant only the biggest or transplant them all if you can’t help yourself.
Hardening off
Seedlings sown indoors, even if they have been under lights and kept cool, will need to harden off—acclimate to living outside—before we plant them out in the garden. After night temperatures have risen reliably into the mid-50s F, place the containers outside where they’ll catch morning sun for a few days before planting the seedlings in their final destination.
Seedlings under lights
A nicotiana seedling separated from the pack.
Room to grow on.
Mexican feather grass (Stipa tenuissima) produces thousands of seeds.
