Trying to coax spring, a few seeds at a time

What could be cheerier right now than a few flats of seedlings on the windowsill? OK, it's still a bit early, but you can dream and plan and send in those seed orders.

If you're really itching to hurry spring along, you could sow some celery, kale, and lettuce seeds indoors. There are even some seeds you can scatter outdoors now. Johnny jump-ups, corn poppies, and Flanders field poppies need a period of

cold and will sprout when conditions are right. Next month, you can start planting seeds of foxgloves, larkspur, radish, spinach, peas, and sweet peas outdoors with some hope, if no guarantee, of success. Gardeners love to tempt fate by pushing the climatic envelope. Planting some cool-weather seeds outside is a low-risk enterprise. If they sprout, you plant more. If they die, you plant more.

It's a bigger problem if you start seeds indoors too early. Then you end up with a lot of big plants with no place to go.

"The most important thing is figuring out when is the right time to plant," said Daniel Cousins, who produces a mind-boggling half-million seedlings a year at Wilson Farms in Lexington. "If you stress the plant by having it in too small a container too early, you don't get any advantage. You want the plant to hit the ground at its peak."

So order those seed packs and check the instructions on them to find the right planting time. You should start most vegetables and annual flowers indoors about six weeks before the last spring frost. Memorial Day weekend is considered a safe planting-out date through most of New England and gives you a holiday for planting. In coastal areas, count back from mid-May. Since gardens have their own micro-climates influenced by many factors, it is helpful to keep an annual record of when the last spring frost (and first fall frost) arrives each year where you live.

The most popular vegetable seeds for starting indoors are tomatoes, followed by peppers. Others worth the trouble include broccoli, cabbage, kale, cucumbers, eggplants, and lettuce. Don't start root crops such as carrots, beets, and turnips indoors. Radishes come up so fast that they don't need the head start, anyway. On the other hand, in most of New England, the growing season is too short for watermelons, winter squash, and pumpkins unless you do sow them indoors (or buy young plants in June).

All this said, don't go overboard with the seed orders. A few flats of seedlings are a lot of fun. More than that is a lot of work.

What you need Get some pots, a drip tray for catching water, some kind of label so you don't forget what you've just planted, a clear plastic cover to hold in humidity, and a soil-less mix for starting seeds.

"I've seen so many cases where people dig up soil from their gardens, which introduces diseases and drainage problems to plants at a vulnerable time of their lives, and those people lose $10 worth of seeds to save $2 on potting mix. A soil-less seed-starting mix also saves you watering time by retaining moisture," said Cousins.

Plenty of seed-starting kits are available, and they are great for beginners. Wilson Farms sells a Window Greenhouse kit by Jiffy for $5.98 that includes a tray with a clear dome for preserving humidity, plus 36 Jiffy pots that can eventually be planted right in the garden without disturbing seedlings' roots. Most garden supply catalogs also have kits.

Sowing If you are using compressed peat pellets such as Jiffy pots, soak them in water until they expand, insert a couple of seeds in each one, and stand them in a drip tray.

If you are using a soil-less seed starting mix, fill the seed-starting containers and then water thoroughly. Alternately, you can put water in the potting mix bag and knead it until it has the dampness of a wrung-out sponge, then pour it into your planting containers. Then sow your seeds as directed on the package.

"The rule of thumb is to sow the seed as deep as the seed is thick," said Cayte McDonough, assistant propagator for the New England Wild Flower Society. Some very fine seeds require light to germinate, including columbine, coleus, California poppy, ageratum, sweet alyssum, strawflower, Shasta daisy, sweet rocket, and snapdragon. Sow those directly on the surface. McDonough usually covers all her seed flats with about an eighth of an inch of No. 1 filter sand, which is a coarse but translucent sand that lets light through. "I've bought it at the local pool supply store, where they sell it for pool filters. The sand holds the seeds and mix in place, especially when watering."

The sand also helps prevent "damping off," a common fungal disease that can cause seedlings to collapse tragically and can occur when damp soil surface is exposed to spores in the air. A very thin top dressing of parakeet gravel from the supermarket will also protect seedlings from damping off. Make it flush with the rim, using a ruler to scrape off excess.

Label your seed flats as soon as they are planted, as most seedlings look pretty much alike.

Water, heat, humidity The soil mix needs to remain constantly moist but not soggy. Cousins avoids sticking his finger in the top of any of the cells to test for moisture.

"That's a great way to spread disease. Also, the top can be a little dry while the bottom is soaking wet." Instead, he calculates when to water by weight. "After you've planted and watered your seeds, lift the tray so you know what it feels like damp. All that weight is the moisture. Then, whenever you lift it and the tray feels light, you know you need to water." Since you don't want to disturb the surface, put water in the drip tray.

Most seed-starting kits include a plastic dome to help preserve moisture and humidity. If you don't have one, make your own using a dry cleaning bag, which is less clingy than plastic wrap, with a straw or chopstick as a tent pole to promote air circulation. Create a few small air holes, too. Beads of moisture on the plastic mean the soil is damp enough.

Most seeds like temperatures in the 70- to 75-degree range to germinate. Artificial lightbulbs hung low over them can supply it. Be careful about putting seed flats in a sunny window, though, or they could fry. Seeds actually prefer bottom heat, so Cousins recommends heating mats, which garden supply catalogs and nurseries sell for roughly $20-$100, depending on size. (See the list of sources below.) Or just put the flats on top of the refrigerator, which also generates heat. When half the seeds have sprouted, move them to a light source. Sprouts need less warmth, so remove any heating mats after germination.

Helping them grow At this point, seedlings need a very sunny window. If you are growing a lot of seeds, you'll need to set up artificial lights. Seedlings need full-spectrum grow lights, not just a couple of 4-foot-long, two-bulb fluorescent shop fixtures from the hardware store. They must be rigged so they are no higher than 6 inches above the seedlings.

If you are a serious seed grower, consider investing in a light stand with stacked shelves of height-adjustable tube lights that provide light to the seedlings below them and bottom heat to the germinating seeds above them. Ken Druse, author of "Making More Plants" has one he's enclosed in vinyl tenting to retain humidity. A small fan circulates the air while a timer keeps the cart lit and heated 18 hours a day.

Keep the growing medium moist and thin the seedlings as needed by snipping off unwanted sprouts at the soil line with manicure scissors. (Don't pull them out; you risk disturbing the roots of the remaining seedling.) You should be left with one good seedling per compartment.

After seeds have developed a set of true leaves, McDonough begins fertilizing them with half-strength liquid fertilizers every two weeks.

Transplanting If you sowed your seeds in one large container of soil-less mix, you will need to transplant them to individual pots after they grow two sets of true leaves. (Don't count the first embryonic leaves they sprouted, called "cotyledons" or "seed leaves.") You may also need to transplant seedlings to a larger pot if they outgrow their original container (because you started them too early?) Always handle seedlings by their leaves, not their stems. If you tear a leaf, the plant will grow another; if you damage the stem, it's done for.

Moving on out A week before your seedlings are due to be planted, move them for about an hour to a spot outdoors that's sheltered from wind. Repeat this all week, leaving them outdoors for an hour longer each day.

If you have a cold frame, all you have to do is move your seedlings into it, and open the lid when the temperature in the cold frame rises above 65, and close it when they fall. Some cold frames do this automatically.

Once your seedlings are planted in the garden, the promise of spring will have become a reality.

Sources: Gardener's Supply Company (800-955-3370, www.gardeners.com). Their $30 APS seed-starting system is outstanding. Also light stands, a $30 plastic cold frame for hardening off outward-bound seedlings, technical support by phone.

Garden Trends (800-514-4441, www.harrisseeds.com). Supplies and light stands.

George W. Park Seed Co. Inc. (800-845-3369, www.Parkseed.com). Seeds and supplies.

Johnny's Selected Seeds (207-437-4301, www.johnnyseeds.com). Seeds and supplies.

The New England Wild Flower Society is taking orders for 225 varieties of wildflower seed through March 15. (508-877-7630; www.newfs.org). Easy wildflower seeds to grow include rudbeckia, New England aster, Echinacea purpurea, columbines, Lobelia cardinalis, celandine poppy, and monardas.

W. Atlee Burpee & Co. (800-888-1447, www.burpee.com). Seeds and supplies.

Wilson Farms, 10 Peasant St., Lexington (781-862-3900). Heating mats, seeds, and seed-starting equipment. Exhibit and retail booth at the New England Spring Flower Show at the Bayside Expo Center March 13-21.

Worm's Way (800-274-9676,, www.wormsway.com). Indoor gardening supplies.