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Once Again, It’s Time to Starting Seeds Indoors

University of Minnesota Extension, Stearns County News
February 15, 2017        
Source:  Beth Berlin, Extension Educator-Horticulture
University of Minnesota Extension
Stearns, Benton, & Morrison Counties


Once Again, It’s Time to Starting Seeds Indoors
By Beth Berlin, University of Minnesota Extension

ST. CLOUD, Minn. (02/15/17) — Each year at this time, it is important to remind gardeners it is time to start some of your seeds indoors.  Time can sometimes slip away from us, and there are some seeds that already needed to be started, but for many the time is now or will be coming in the next month or so.

As a reminder the key to growing good transplant plants is having the proper light, temperature, and humidity.  Often the most common problem is inadequate lighting. Supplemental lighting is needed if you are starting seeds indoors.  An inexpensive lighting option is to use shop lights with a 40-watt fluorescent that can be adjusted to different heights above the flat or container of seeds.  The light should be placed within two to four inches above the tallest seedlings.  If the lighting is placed too high the plant may become “leggy” as it reaches for the light.  Seedlings need to be placed under this direct light for 14-16 hours each day.  Timers may be used with the lights to provide consistency and ease for the gardener.

It is critical from the very beginning to provide adequate water to the seeds or seedlings.  The soil should be kept moist but not wet.  The starting medium must be loose, well-aerated, well-drained, and sterile.  Pre-mixed seed staring mixtures can be used or a soilless mixture consisting of equal parts of vermiculite, and peat moss can also be blended. Most importantly, using sterile mixture is critical to the health of the seedlings; that also includes using sterile containers. Wash containers with one-part bleach, nine-part water mixture to clean the trays, pots, or even recycled containers or cans.  Another option is to use boiling hot water to clean the containers. 

Once you’ve cleaned the containers and have a good, sterile growing medium, fill the container to one-half inch below the rim. Read the seed packet for specific instructions on planting depth; some seeds have different requirements including chilling or scarifying (scratching the seed coat). Once you’ve planted the seeds, water them in carefully.  Using a spray bottle will allow you to water with a fine mist without disrupting the growing medium or seeds.

Cover the containers using plastic domes or a sheet of polyethylene plastic.  The containers will now need to be placed in a warm location with a constant temperature of 60-75°F.  Using a growing heat mat can help maintain consistent temperatures. Heat is critical to the success of the seeds’ germination; placing it in a window sill is typically not a good idea because it tends to be too inconsistent in temperature and can become too cool for germination.  As soon as germination occurs and you see emerging plants, loosen the plastic cover.  Continue to water the containers so that the growing medium is moist, but not wet.  Begin fertilizing once the seedlings have several sets of true leaves using diluted fertilizer at one-quarter strength every week; water with plain water as needed the rest of the week.

Here is a list of when to start common plants indoors:

• Early February: geraniums, wax begonias, and violas or pansies
• Mid-February: dusty miller, fountain grass, impatiens, larkspur, lobelia, and celery
• Early-March: ageratum, coleus, dahlia, petunias, rudbeckia, snapdragons, verbena, vinca/periwinkle, broccoli, cabbage, cauliflower, and head lettuce
• Mid-March: bells of Ireland, candytuft, cleome, dianthus/pinks, hollyhock, African marigold, ornamental pepper, annual phlox, salvia, sweet alyssum, peppers, and eggplant
• Early-April: amaranthus, aster, baby's breath, bachelor buttons, celosia, cornflower, four o'clock, French marigold , morning glory, nasturtium, ornamental basil and kale, and tomatoes
• Mid-April: cosmos, sweet peas, black-eyed susan vine, and zinnia

With some work, starting seeds indoors can be an inexpensive way to get a wide variety of plants in your gardens.  Visit the University of Minnesota Extension website at: and search “Starting Seeds Indoors” for more information.


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