Planting seeds indoors early in the growing season saves money over buying established plants for the garden. Growing plants from seed also allows the gardener to grow a wider variety of plants than what is offered locally. Starting seeds indoors requires the same basic elements as growing outdoors: seeds, potting medium, water, and light. When planting seeds indoors, you will be able to control these conditions to ensure the healthiest plants for your garden.
First, you must know when to begin planting seeds indoors. Different seeds have different rates of germination; this information is generally found on the seed packet. Start by knowing the approximate date of the last frost for your area, and count backward the number of weeks suggested on the seed packet.
Next, choose a container for sowing the seeds. Specially designed seed trays and flats are widely available at many garden shops. Some growers prefer to use peat pots or peat pellets for planting seeds indoors, because the entire container can be planted into the garden. Ordinary household items such as egg cartons or margarine tubs may also be cleaned and reused as seed trays. Be sure to poke drainage holes in the container before filling.
A lightweight potting mix is ideal for planting seeds indoors. Commercial mixes have been sterilized to kill any weed seeds and soil-borne diseases. It is also possible to create a mix with peat, sand, loam and vermiculite. Avoid using heavy garden soils or clay soils, because the tender roots of the seedlings may not be strong enough to push through them.
Sow the seeds according to the directions on the seed packet. Some seeds need to be planted in shallow holes made with a pencil or toothpick poked through the soil. Finer seeds need only be scattered over the surface, particularly if the seeds need light to germinate. Mist the seeds lightly and keep them moist, but not soggy.
Next, place the seed trays in a sunny window and keep them warm. Most seeds will need temperatures between 65-80 degrees F (18-27 degrees C) to germinate. Once the seedlings have emerged, they will generally need 12 hours of light each day. If there is not adequate sunlight, fluorescent grow lights can help ensure the seedlings receive enough light to thrive.
Continue to keep the seedlings moist and begin fertilizing them with half-strength fertilizer once a week, after the second set of leaves have emerged. About two weeks before planting time, begin hardening off the seedlings, or gradually introducing them to the outdoors. Place them outside in a shady location, increasing their sun exposure gradually each day, and bring them in each night until all danger of frost has passed. At this point, the plants are ready to transplant to the garden.
