Category Archives: seed starting

Starting Seeds Indoors

It’s only January, but seed catalogs are arriving in the mail and gardeners are dreaming of summer. One way to get a head start on your vegetable garden is to start your own seeds indoors. It is relatively inexpensive to create your own seed-starting set up. In the long run you will save money because seeds are cheaper to buy than plants. If you want to take it a step further, you can save even more money by saving seeds from your favorite plants to start next year.

One of the great benefits of starting your own plants indoors is the amazing variety of seeds available at garden centers and in catalogs.  It’s great fun on a cold, snowy day to browse seed catalogs and find new and interesting varieties of your favorite vegetables to start for your garden.

Each type of seed has its own germination and growing requirements, but most seeds need to be started 6 -8 weeks before they will be planted in the ground.  To get seeds to germinate, you will need adequate light and soil temperatures above 70 degrees.  A warm sunny window may be adequate, but to ensure good germination and sturdy plants some extra help is often required. Cool soil temperatures and too little light will result in poor germination and spindly, weak plants.

To provide good light, use two four-foot florescent shop light fixtures suspended close

Shop light suspended from chain.

Shop light suspended from chain.

over the seedlings. The key to using florescent shop lights is to have one cool white and one warm white tube in each light fixture.  The combination provides the proper light spectrum for growing plants. Keep the lights on for 16 hours a day using a simple light timer. To avoid leggy, weak plants, keep the lights very close to the tops of the plants. This can be accomplished by hanging the lights from chains that you can adjust up or down.

To get the seeds to germinate you will need a warm, moist (not wet) environment. To ensure the proper environment for germination, use peat pots placed in seed starting trays with clear plastic covers.

Seed tray and clear cover

Seed tray and clear cover

The plastic covers keep the peat pots warm and moist until germination. Use a seed starting soil mix in the peat pots. Regular potting soil and soil from your garden are too heavy for starting seeds. Most seeds need soil temperatures of 70 degrees or above to germinate. To ensure adequate soil warmth, use heat mats under your seed starting trays.

Heat mat for starting seeds.

Heat mat for starting seeds.

Once the seeds have germinated and are growing, the heat mats and clear covers should be removed. The trays, covers, pots, starting mix and mats are all available at local garden centers.

Partial set up showing on light fixture.

Partial set up showing one light fixture.

Two four-foot shop light fixtures placed side by side fit perfectly over two standard 10.5” x 21” seed starting trays set end to end. Each tray holds 32 – 2.5” peat pots.

As the seedlings grow, raise the lights little by little to keep them just above the plants. Water just enough to keep the peat pots moist, but not soggy. The pots should not be sitting in standing water. Too much water will lead to poor germination and weak plants. You can also use a spray bottle to mist the plants to add moisture.  Once the plants are growing and develop true leaves, a weak solution of a Miracle-Gro type fertilizer will promote strong plants. Put two or three seeds in each peat pot to make sure at least one plant germinates per pot. As the plants grow,

Trays under lights after germination.

Trays under lights after germination.

keep the strongest plant in each pot and thin by snipping the weaker seedlings near soil level.  Always snip, don’t pull. Pulling out the weaker plants can disturb the roots of the remaining strong seedling.

Happy plants.

Happy plants.

About two weeks before you plan on putting the plants in the ground, start hardening off the plants by placing them outside for part of the day. Start off slowly! The leaves will be tender and susceptible to damage from too much sun or wind.  Start with a few hours in dappled shade on a mild day. The daytime temperatures should be above 55 degrees. Day by day, the plants will become stronger and can be left out longer and in more direct sun. Do not leave them out overnight if the temperature will dip below 50. Peats pots are small and can dry out very fast.  Make sure the plants have adequate water while hardening off. One way to avoid plants drying out while they are hardening off is to transplant the seedlings from peat pots to 4 ½ inch or one gallon pots with regular potting soil. The plants really take off with the extra room and the larger pots are not as prone to drying out.

After two weeks or so, your hardy plants are ready to go into your garden.

For more information check out these publications from CSU Extension:

Plantalk 1034: Starting Seeds Indoors

Fact Sheet 7.409: Growing Plants from Seed

Fact Sheet 7.602: Saving Seed

Written by Mark Zammuto, a Denver County Master Gardener

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