This threatens to be a long and rambling screed, but I promise it will be full of useful information. It may be a little late for some types of plants and some locations, but my hope is that it will be a resource to be bookmarked and returned to over time. Note that you can get a bigger view of any photograph here just by clicking on it.
There are plenty of good reasons to start your own seeds: to take full advantage of the vast selection of plant varieties available; to save money (in some scenarios); to ensure you're not bringing disease home to your garden (as was the case a few years ago, when plants infected with blight at a large commercial greenhouse were distributed to the likes of Lowe's and Home Depot, and a cool wet summer provided perfect conditions for the spread of an epidemic). For me, the number one reason for starting my own seeds is that I get about a 2-month jump on gardening season. Instead of waiting until the conditions are right for planting out starts from a garden center, I'm busy grinding dirt under my fingernails and nurturing little green babies while it's still snowing outside.
This time of year, seed displays start sprouting up everywhere (at least around here, they do) – the grocery store, the hardware store, sometimes even drugstores, and big chains like WalMart, Target, K-Mart, Home Depot, Lowe's...in addition to the many nurseries, greenhouses, and farmer's supply centers. I prefer to buy my seeds online (where seed suppliers are plentiful) so that I can be picky about the varieties I grow, researching carefully for hardiness, growth habits, flavor quality, nutritional needs, potential yields, pest & disease issues, etc., etc., etc. These days, I buy most of my seeds from Johnny's – my successes and failures over the years have led me to trust them best. I also buy a few varieties from Kitchen Garden Seeds that I can't seem to find elsewhere. But I've been at this for a long time (almost 30 years!) and have a pretty big garden; if you're just getting started, by all means grab a few packets of whatever intrigues you, wherever you find them!
You'll need some dirt to grow your seeds in. Don't try using soil dug from your yard – there's no telling what might or might not be in it (could have fungus or bacterial diseases; may not have the right, or any, nutrients). There are plenty of bagged potting mixes available, both conventional and organic. Choosing one is a bit of a crapshoot, but in general terms, you want soil that is neither overly light (won't hold water and your plants will always be thirsty) nor overly heavy (holds too much water and your plants' roots will rot). And you want dirt that offers some nutrition. There are mixes that have fertilizer blended in; I prefer to grow without chemicals, so I don't use these. My recommendation is for a good organic potting mix; I currently have a big bag from Espoma.
Most places that sell seeds will also sell seedling flats or trays, often in a kit that includes the little divided-cell inserts and a clear plastic 'humidity dome' (just a snug-fitting cover that will keep moisture in while the seeds germinate). I have stacks of trays and lids collected over the years, and every few years I buy a selection of cell inserts in different sizes. But you can start seeds in anything that will hold dirt and allow water to drain out the bottom: soup cans, egg cartons, foil baking pans – just poke some holes in the bottom and put a tray underneath to catch excess water. And you can use plastic bags or plastic wrap to keep the moisture in. If you get serious about growing, Novosel has everything you need.
Seedlings need light to grow big and strong. You can always just tuck your seedlings in a sunny windowsill, but unless you have good strong sun for most of the day, your seedlings are likely to be weak and 'leggy' – limited foliage on long flimsy stems, pale anemic plants lacking in good photosynthesis (in essence, the process by which plants make food for themselves). Branded Grow-Lights can be scandalously expensive, but any flourescent light with a full-spectrum bulb will give your little plants a distinct advantage.
I have a pretty slick little 'greenhouse', sprung from my husband's practical genius. We picked up a rack of steel Metro shelving on one of our Costco trips, @ $80 for a 4' x 1.5' x 7' unit with five shelves and four brawny casters. Each shelf is the perfect size for two or even four 10" x 21" standard seedling trays, with one or two standard fluorescent shop lights dangled from the shelf above.
A pair of 1-inch split rings with two 1-foot lengths of light-duty steel chain and a couple of small S-hooks makes a nice adjustable hanger for each shoplight, so you can start them right down on top of baby plants and raise them up as the plants grow taller. Wrap the whole thing in heavy plastic sheeting (to keep in warmth and humidity), add a power strip on a timer and you're in the seedling business. If your setup is in a cool spot, you can add a clip-on work light with a 100-watt incandescent bulb below the bottom shelf, which will keep the interior warm and cozy for the kids. You can also buy electric warming mats to put under the trays, but again: scandalously expensive.
Before you start putting seeds into dirt, make sure the dirt is good and damp/moist. Better soil mixes will be plenty damp in their plastic bags (which will be evident to some degree by their weight). If the soil is very dry, you'll need to 'pre-moisten' it. Dump some into a bucket and, adding a little warm water at a time, mix and stir until all of the dirt is uniformly moist. The dirt may need to sit for 15 or 20 minutes to absorb the water. This is an important step: if the soil is very dry, when you try to water your seedlings the water may just sit on top of the dirt or, worse, run off, taking a bunch of dirt with it. If your dirt doesn't absorb water well in the pre-moistening stage, abandon it and try another mix. I once threw off an entire season with water-repellent dirt; my seedlings were uniformly weak and undersized and many didn't survive transplanting. Golden rule for dirt: damp or moist, but never wet and never dry.
I like to start groups of seeds in a single tray of dirt (see the lower shelf in the greenhouse photo above). Once the seedlings are established and strong, I carefully lift them out of the dirt, select the strongest ones, and pot them up separately in cells or individual pots. Larger, faster-growing plants can be sowed directly into cells or pots, two or three seeds, then the weaker seedlings removed. Some plants are better off started directly in the garden. I'll get into that later.
Spread some newspaper over a tabletop or counter & let's get to work. Fill a tray with dirt to a uniform depth of about 2 inches, gently pressing down to lightly pack the soil. Carefully distribute seeds for each variety over the surface in a patch about 4 x 5 inches. Don't crowd the seeds – there should be at least 1/4 inch between them (although this can be hard to do when the seeds are tiny...and impossible to do if your fingers are wet). Leave about an inch between each patch, and mark each one so you know what's in it. You can buy specially made plant markers, or you can use popsicle sticks, tongue depressors, plastic spoons – whatever works. I discovered this year when I ran short of markers that small clothespins work great (pack of 50 for $1 at the dollar store!).
(The tray I'm using here was already host to this season's tomato and pepper starts; I'm re-using the dirt to start basil, cilantro, and dill. Already sprouted but not yet big enough for transplanting are a patch of celery seedlings.)
Once the seeds are all laid out, spray the surface with a fine mist until it's very damp, then sprinkle about a 1/4 inch of dirt all over and press lightly to pack it. Mist again, then cover the tray with a humidity dome (or do as I did here – just lay plastic bags over the surface) and place it somewhere warm. Temperature is important: in general, seeds don't like to grow in cold dirt. I've found 65 – 75°F to be ideal (that's soil temperature, not air temperature). You can put the tray under lights at this point, but most seeds will sprout in the dark. Just be sure you have a light source ready for when they pop out of the soil and start to reach for the sky.
My favorite part of seed starting is the daily checking for signs of sprouting. On average, seeds will take 5 days to a week; some may sprout in as little as 2 days, some may take several weeks (as did the celery). Below, left to right: basil, cilantro, dill.
After the seeds have sprouted, you can remove the plastic covering. You don't want too much moisture to build up, or you may start to grow mold or moss in addition to your happy plants. Good air circulation is essential. If most of your seeds have sprouted but you're still waiting on one or two varieties, better to remove the plastic and just pay special attention to the moisture applied to the unsprouts. At this stage, I continue to use mist from a spray bottle for watering, as even a sprinkle from a watering can may be enough to dislodge little seeds and sprouts. Wait before misting until the surface of the soil seems uniformly dry, but never let the soil below the surface dry out. Remember: damp or moist, but never wet and never dry.
You can transplant the seedlings any time after they get their first 'true' set of leaves; the first two 'leaves' are the cotyledons – really just part of the seed.
Even the daintiest seedlings* are surprisingly resilient: you can fully extract them from the dirt, gently tug their roots apart, even leave them sitting naked on a tabletop while you pot up their siblings, and they'll be fine once they're back in the dirt and sufficiently watered. However, you should always take care to handle them by their leaves, and not by their stems.
*There are some exceptions, of course. Poppies seem to wither and die if you so much as contemplate messing with them. And I've been told that any of the cucurbits – melons, squash, cucumbers – resent transplanting. This hasn't been my experience, although I start them in their own pots and transplant them with a full plug of dirt surrounding their roots.
Hold a group of seedlings by their leaves and use a long narrow object (plant marker, knife, pencil) to gently loosen the soil and lift out the roots. If you feel any resistance, loosen the soil some more so you don't tear the roots.
Gently separate the roots so that each seedling is detached.
Fill the individual pots or cells with (moistened) dirt and gently pack it. Use your long narrow tool to make a hole for the seedling: stick the tool straight down to the bottom in the middle of the pot, and rock it back and forth to widen the hole. Chances are you'll have more seedlings than you need, so select the strongest ones for transplanting: ones with the stoutest stems, the most and largest leaves, the most developed roots. Pick up one of your seedlings, by the leaves, and lower the roots and stem into the hole (you can use your tool to gently push the roots down).
Sink the plant deep into the pot, leaving just a little bit of stem and the leaves above the surface (this will make for a sturdier stem). Gently pack the dirt around the stem and add more dirt if necessary. Mark the plant and give it a good drink of water (OK to use a watering can or the faucet now).
Keep the potted seedlings under light, warm, and carefully watered. Wait until the soil surface is dry before watering (or watch for signs of minor wilting). Over-watering is much worse than under-watering – plants will bounce back quickly from getting a little dried out, but once you start to rot a plant's stem or roots from too much watering, there's no bringing it back.
You can give them a little weak fertilizer, but if you're using good soil, they may not need it. More important to keep their light source strong; if the seedlings start to look 'leggy' – if their stems seem thin and spindly – try bringing the light closer (or getting a light if you've been relying on a sunlit windowsill). Fluorescent bulbs don't throw off much heat, so you can bring the light almost close enough to touch the plants, with no risk of burning them. If you do decide to fertilize, make sure you use a very weak solution so you don't burn the roots. I use Neptune's Harvest, well diluted with water.
It's a good idea to handle your seedlings, gently brushing along their tops each day. This simulates exposure to wind and prompts them to toughen up. When it gets close to planting time, you'll need to 'harden off' your seedlings, taking them outdoors to expose them to the elements a little at a time. Find a shady spot to start, and on a warm calm day, put the seedlings outside for 15 minutes or half an hour. Slowly expose them to increasingly more direct sun, wind, and temperature changes. Avoid putting them out on very windy days, and never when the temperature is below 50°F. Gradually cut back on watering, too, letting them dry out a little between drinks. This way, when you finally plant them out, they'll be able to survive without such frequent pampering.
It's likely too late, for this year, to start your own tomatoes, peppers, eggplant, broccoli, cabbage. But you can still start annual herbs, lettuces, some annual flowers. It's even a bit early yet for things like squash or cucumbers, or sunflowers or nasturtiums; I generally start these about 3 weeks before I intend to plant out. Seed packets will give you information on when to start different varieties indoors, usually given in weeks in advance of your area's 'frost-free' date.
Plenty of vegetables are better off started directly out in the garden, either because they're fine with colder temperatures (peas, spinach) or because transplanting them would be ill-advised (carrots, beets, greens for cutting). I sometimes start peas indoors just to guarantee more consistent germination; in fact, I did so this year but was a distracted steward and overwatered them (it can happen to anyone) – and got inconsistent germination in spite of myself. I'll plant them out this week, and direct-sow more of them so I have a full bed's worth. I'll be planting salad greens, too, this week, and root vegetables.
In a couple of weeks, I'll start Delicata squash, pickling cucumbers, and a variety of sunflowers inside. It's so hard to predict planting-out time these days; for so long, I waited until mid-June just to be sure and miss any freezing temperatures. The date has slowly moved back into May over the past few years, and last year it was so reliably warm, even overnight, that I planted the first weekend in May. Stand by. I promise to be almost as wordy at planting time.
If you have questions, or suggestions, or need to call me out on something that sounds wrong, please leave a comment below. Comments are moderated, so they won't show up until I approve them, but I'm usually pretty quick on the 'Publish' button.