Seed Starting Indoors
It’s that time of year again, to begin thinking about starting seeds indoors. Below is an article written by our experienced seed starter Master Gardener Debbie MacCrea!
Seed Starting Indoors
By Master Gardener Debbie MacCrea
There are many benefits to the practice of starting seeds of both vegetables and ornamentals indoors, well ahead of their safe outdoor planting time. Perhaps my own greatest motivator is what the ritual does for the winter-weary spirit, and that it allows extra months of real, productive garden work at a time when summer sun is dreams away. I’ve found, over several decades of gardening, that there are more “leisure” hours available to me in winter, when the work I’d love to be doing can’t be done, for the dreaming and planning, the designing and mental rearranging of elements of my landscape. Then summer’s labors really pay off. There is good reason we say “the dead of winter”! But when we fill those anxious, impatient months with planning, planting, nurturing and designing, the benefits are manifested in earlier, healthier, more productive and beautiful gardens all spring, summer and fall.
By starting seeds indoors weeks before they would survive the outdoor conditions, the gardener can extend the season of vegetable and flower production by days, weeks, even months. With long season vegetables, like peppers, melons, winter squash or eggplants, growing seedlings can mean the difference between little or no harvest and a bountiful one- at least for Northern gardeners.
Secondly, by shopping the countless seed sources, we have far greater selection of varieties. With vegetables, this can mean the characteristics of flavor, color, size and period of harvest are yours to choose, while neighboring gardeners settle for whatever few varieties are stocked by local merchants, varieties which may have been chosen, like some of the tasteless produce found year-round in all supermarkets, for their mass-appeal or shipping ease, rather than the features that matter to YOU.
Third, it is possible, even relatively simple to grow seedlings which are healthier, more beautiful, and better timed to be of perfect size and readiness for planting out when YOU are ready to plant them. In 2009’s summer of “The Blight”, those who raised their own tomato seedlings at least had that head start to a healthy tomato harvest.
Lastly, the old bottom line- money! For the same money you would spend purchasing half-dozen 6-packs of seedlings, you can grow dozens of varied, even exotic plants of your choice.
Time here for a little honest disclaimer- Once you’ve experienced the heady magic of growing your own, you may not find you’re saving any money. The seedsmen sure know when to hit with their irresistibly beautiful catalogs. I find myself trying new and different (and more expensive) varieties each year. But, oh the rewards!
The necessary elements in this venture are simple: A growing medium, containers and labels, seeds, light, nourishment and water.
The growing medium used in the initial stage- GERMINATION- is usually not “soil”, definitely not ordinary garden soil. The germinating seed needs only a medium to support it and its tender new growth upright and requires excellent drainage and lots of air spaces, the pores through which water, oxygen and roots move. These necessities can be supplied by a totally soil-less mixture of equal parts milled sphagnum moss, vermiculite and perlite. These last two ingredients are manmade products of volcanic ash or rock origin, and are excellent for absorbing and transporting water and nutrients to seeds and growing roots. For transplanting and growing on, commercial potting mixes (or homemade mixtures of compost, garden soil and peat, vermiculite or perlite) are ideal. Garden soil alone- even your best- tends to compact and/or crust over, with not nearly the friability needed by tender new stems and roots.
Containers and Labels- What you choose in which to plant and grow your seeds is limited largely by your ingenuity, tempered by reasons of space, available light and the tolerance of your family. Do keep in mind that any container MUST have drainage holes, and ideally a slightly larger one without holes in which to set it, allowing bottom watering. All must be scrupulously clean. If reusing old plastic or ceramic pots, scrub in soapy water (use an old bottle brush), and rinse in a solution of 9 parts water to 1 part chlorine bleach. A fungal disease known as “Damping Off” is perhaps the #1 enemy of young seedlings. It attacks quickly and is irreversible once symptoms show – the lower plant stem will appear shriveled, though the leaves appear healthy; the plant will topple over and die. The fungus thrives in over watered, overcrowded conditions, especially when too heavily fertilized (nitrogen in particular). It can over winter in old containers, or be carried by non-sterile soil mixes. If you see it, remove affected plants immediately, increase air movement, decrease water and hold off on fertilization for a few day or more.
Labels can be Popsicle sticks, strips of metal from old window blinds, plastic strips cut from milk jugs….use a wax pencil or indelible marker to record plant name, date sown and perhaps expected germination date.
Seeds- Gather together all the seeds you’ve saved, purchased or inherited from gardening friends, along with all the information about each variety’s growth and needs. Most of this will appear on the seed packet or in the seed catalog. You’ll want to know: light or darkness requirements for germination, temperature needs for germination and growth, anticipated # of days for germination, and # of weeks before planting out into the recommended outdoor conditions. The first two are fairly general. Most vegetable seeds require darkness (soil coverage) to break dormancy. Flowers are more varied in their demands. Most seeds of both flowers and veggies need 70 to 80 degree temps (SOIL temp) for germination, then prefer 60’s to 70’s to grow on, with 10 degrees lower in nighttime.
The last two categories vary even more from one species to another, but are important to know. Ideally, you want to grow plants that are mature enough to endure the fickle conditions of life in the real world once set out, but not so old as to be “stagnating” in their restricted growing environment. Plants should be able to grow on unchecked from germination to planting out. Some plants, cauliflower for one, may not ever recover if its growth is held back by a long spell of waiting for the weather to settle out. If germination is quick (5-10 days), this must be factored in; if it takes weeks, as some fickle flowers can, this must be known as well. So, get out a calendar and count back from the date of the last frost anticipated for your area, (CCEcan help if you don’t know this critical date) and sort your collection of seed packets into groups which require approximately equal # of weeks to planting out. Don’t be tempted to plant everything at once. This spaces out the work of caring for your growing seedlings as well, so that, for instance, all your seedlings needn’t be transplanted to larger pots all at once.
Be sure your seeds are of good quality. Federal standards regulate allowable germination percentages. But if seeds are not stored at appropriate temperatures and humidity levels, their vigor declines rapidly. The embryonic seed actually consumes some of its stored nutrients just to survive dormancy. The longer this goes on, the less vigorous the seed. More of that stored energy is needed, after germination, to grow the first leaves, called cotyledons, or seed leaves. Only with the first “true leaves” can the new plant begin to manufacture its own energy. Often, beginners blame a seedling’s failure on damping off or other factors when the real culprit may be poor seed vigor.
Light- An ideal arrangement of a few double-tube florescent light fixtures in an out-of-the-way place is well within most people’s reach. (Priorities! You’ll soon, though, find yourself scanning your home for more and more space!) Plant “grow lights” aren’t necessary, unless you need your seedlings to be in bloom before planting out. A fixture with one cool white and one warm white tube is best, but even that isn’t critical. You can make better use of available light by covering sheets of cardboard with used aluminum foil to reflect more light rays onto your plants rather than it dissipating into surrounding low light areas. Prop these around the seedling flats. Lights should be close to the tops of your plants without touching them- from 2-4 inches above is best. If the leaves droop- raise the lights; if the stems stretch out leggy and spindly, lower the lights- your light is too weak.
Sunny windowsills are rarely suitable. Often drafty, the plants will receive weak light for part of the day, then occasionally hot, baking conditions which can dry soil too quickly. Wintertime sunlight is, at best, of a low intensity.
Once your seeds are sorted by needs, gather the remaining equipment. Spread a sheet of newspaper out on your table, fill all containers to within ½ inch of their tops with your growing medium and set them in shallow pans of warm water until the soil appears darker. It is much easier to thoroughly moisten the soil before sowing than to have to water afterward, displacing your carefully positioned tiny seeds. Make labels for each kind of seed and insert them in the appropriate place. It’s quite easy to get carried away placing seeds, only to forget which variety you put where.
Place 2-3 seeds per pocket, if using divided packs; sparsely in rows if using flats. Seed should be covered (I use pure vermiculite- it doesn’t crust over and combats the damping off fungus) to a depth of no more than 3 times their size. Fine, dust like seed should be merely pressed gently into the soil surface. This covering needn’t be moist- it will absorb enough moisture from the soil below. Cover the flat with a sheet of newspaper for darkness, or plastic to retain moisture, creating the humid environment needed for germination. Set flats in a warm place- above your refrigerator or hot water heater, near a wood stove, over a radiator. (Remember that nothing is quite as appealing to a housecat as a tray of loose soil!!) Check daily for the first signs of growth and remove the covering as soon as several green “elbows” appear. If only a few have germinated, find a way to keep a covering over those which haven’t yet come up. If all seeds planted in the same flat have approximately equal # of days to germination, this should not be a problem.
Set flats immediately under lights; they should get 12-16 hours of good light per day. Darkness is equally important, as plants “digest” the energy they’ve gathered during light hours, growing more on the sides away from the light source. That is why, if your light source is strongly lopsided, so your plants will be!
Water and Fertilizers – As soon as seedlings grow beyond their cotyledons, they require supplemental fertilization. Water-soluble plant foods are perfect for seedling programs. For the first week or two, this should be diluted to half strength. Water only when the soil is dry! The over zealous gardener often kills or weakens their young plants by over watering. If your setup uses hole-less trays beneath the seedling flats or packs, bottom watering works beautifully. If water remains in the bottom tray ½ hour after watering- drain it off, Next time- use less. As seedlings grow, fertilize every 3rd or 4th watering, no more than every 10 days.
Thinning and Transplanting- With the arrival of the seedling’ first “true” leaves, it’s time to thin or transplant, leaving the strongest single plant per pod so that it can grow to its best potential. If you haven’t time for transplanting right away, snip or pinch off (don’t pull up- too much root disturbance) excess seedlings, leaving 1/8th inch of space for each. When you have time for the more tedious, careful work of transplanting, first water the flat well. Seedlings experience less shock if their stems are turgid. Using a table fork or pencil, gently prick out a group of seedlings; separate out only one and, holding it by a leaf, not the tender stem, move it to a new pot. This should be filled with a good quality potting soil, with a hole made for the new seedling using the pencil as a “dibber”. Settle the seedling at least as deep as it was previously growing, deeper if it is a tomato, pepper or marigold. These have the ability to grow roots all along the stem as it is buried, giving greater growth potential. Plants which have a leafy crown- such as lettuce, cabbage and many flowering plants should never have soil pushed into that crown as it encourages rot.
Hold off on watering for a day, shading the new transplants from strong light if they appear wilted. Then resume their routine and GROWON!! Transplant seedlings as often as they need more space (root space especially) until ready to plant out. Remember: Sow sparsely, thin ruthlessly, transplant early, and often, if needed.
Many flowering plants, but few vegetable seedlings, benefit from being “pinched” as they grow, encouraging compact, bushy growth and therefore more flowers. Simply pinch above a leaf node, removing the tip growth; this signals the plant to branch out. Plants also benefit from the loving touch of the gardener. Every few days, lightly brush your hand over the growing seedlings. This, as well as the gently moving air from a fan, encourages stocky, healthy growth- a little early “hardening off”.
Cornell’s Vegetable Growing Guide
Choose the best Vegetable Varieties for Home Gardens.
Need to know how much fertilizer or lime to add? Learn how to test your soil. (pdf)
Resources for Youth