Starting seeds indoors
Starting garden plants from seeds indoors can be an enjoyable project for any gardener. It’s a relatively inexpensive way to grow a wide variety of plants. Many garden favorites are found in a greater variety of colors, sizes and growth habits as seeds rather than as started plants.
Sowing Seeds
Sow fresh seeds individually into each container according to package directions. If you are unsure about seeding depth, a rule of thumb is to plant a seed two times as deep as its width. Plant a seed deeply enough that one more seed could be placed directly above it.
Identify each container or tray with a tag. Use a permanent marker.
Some seeds require light to germinate.
Cover them with a thin layer of fine vermiculite, porous enough to permit light to penetrate, yet keep the medium moist enough to encourage seed germination.
Place cell packs containing seeds that need darkness for germination in dark plastic bags or cover them with several layers of newspaper until the seeds sprout.
When using older seeds with lower germination rates, plant two or more seeds per cell.
Once the seedlings have developed true leaves, cut all but the healthiest one off at ground level with scissors.
Avoid separating or pulling the unwanted seedlings, as this could damage the roots of the ones you want to keep.
Light
It’s much better to grow seedlings under fluorescent or LED lights than to rely solely on natural light, even in a greenhouse.
Some brands of lights are sold as “grow lights,” designed to provide light in specific ranges required by plants. Standard fixtures with two “cool white” fluorescent tubes per fixture also give plants adequate light and are inexpensive.
A combination of cool white and natural daylight tubes provides good light for plants and is more appealing to people.
Hang lights from chains to ease raising them as the plants grow. Keep lights no more than four inches above the tops of your seedlings – as close as two inches is ideal. Lack of light is the major cause of elongated, skinny stems.
Plants need 12 to 16 hours of light daily. Don’t leave the lights on continuously, as many plants need some dark period each night to develop properly. A simple timer can be part of the set-up so lights are turned off and on automatically.
Watering & Fertilizing
Keep the potting mix moist while the seeds are germinating. Water the surface gently with a spray bottle so you don’t wash the potting mix out of the containers, but be careful not to let the potting mix inside the container dry out from a lack of water. It is easy to mist the top of the potting mix and let the rest of the container become dry. You also can add water to the tray and allow it to move up into the mix.
In either method, drain the excess water that remains or accumulates in the tray to keep the roots healthy.
Seedlings draw energy for germination from nutrients stored in the seed. They don’t need fertilizer until they have several sets of true leaves.
Seedlings grown in a soilless mix will benefit from a weak general-purpose water-soluble fertilizer mixed at one-quarter strength. Fertilize only once a week.
Transplanting
Transplant seedlings that outgrow cell packs into containers that are one to two inches wider in diameter than the cell packs. Larger peat pots or plastic cups with holes punched in their bottoms work well.
Lift seedlings by the rootball using a spoon or plant tag for support if necessary. Never hold the seedling by its stem; you may crush it or harm the growing tip.
If you need to steady the plant from above, lightly hold the plant by a leaf.
A seedling that has lost a leaf can grow another, but a seedling that has lost its main growing point may not survive.
Larger seedlings in larger containers will require more space and often another set of lights.
Moving Seedlings Outdoors
Plants started indoors will not have been exposed to full sun, wind or fluctuating temperatures. If they are not gradually accustomed to the outdoor environment, a process called “hardening off,” their leaves may be scorched by sun or wind. They may even wilt and die.
Two weeks before planting outdoors, move seedlings outside. Start by putting them outside for a few hours in the shade during the warmth of the afternoon, protected from wind. Bring them back inside before temperatures start to drop at night.
Each day, leave the plants out a little longer and expose them to a little more direct sunshine. By the end of two weeks, unless freezing temperatures are forecast, the seedlings can stay outside in a sunny area until you are ready to transplant them into the garden.
Planting Outdoors
Once they have been hardened off, seedlings can be set out in the garden. Transplant on a cloudy day or late afternoon when the sun has passed its peak.
Hardened-off plants may wilt when first exposed to full sun, but they generally recover within a day or so. Row covers and other types of plant protectors can help plants get off to a good start in the garden by reducing damage from wind and temperature fluctuations.
When transplanting seedlings grown in peat pots, newspaper pots, cow-dung pots or any other containers made of organic matter, trim the collars of the pots down to soil level so they don’t wick water away from the root zone. To encourage roots to spread into the garden soil, carefully cut or tear holes in the bottom of the pots.
Article adapted from University of Minnesota Extension
