How to make your seedlings thrive

By Linn County Master Gardener Lisa Slattery


Many gardeners like to start seedlings at home. Starting seeds has advantages: growing unique varieties of flowers and vegetables not available at garden centers; saving money; and personal satisfaction of nurturing plants from seed through harvest.  Starting seeds indoors isn't rocket science but it does have a few challenges.  The key is to provide a thriving environment.   

When planting seeds choose containers that have good drainage.  You can use flats from garden centers, empty yogurt containers, gallon milk jugs cut in half or small pots from your garage.  Make sure you clean any used or recycled containers with soapy water and disinfect by dipping them in a solution containing one part chlorine bleach and nine parts water.  Plant seeds in a sterile, well draining potting mix.  Seed starting mixtures available from garden centers are a good choice.  If you start with clean containers and sterile potting mix you'll avoid a common problem with seedlings called "damping-off" which is the collapse and death of young seedlings caused by fungi.  This occurs with  poorly drained potting soil, overcrowding and excessive watering.  Make sure you sow seeds thinly and allow the potting mix to dry somewhat between waterings once your seeds have germinated.  If you use peat pots and notice whitish or brown mold starting to grow on the surface of the pots that's a sign of too much moisture.

Another requirement for healthy seedlings is proper light. Sufficient lighting will ensure short, stocky transplants, not tall spindly ones that can collapse easily.  Most home gardeners don't have a greenhouse and a sunny window won't provide enough light for seedlings to flourish.  Find a place where you can hook up or hang a standard fluorescent shop fixture containing two 40-watt tubes (one cool white and one warm white).  Place seedlings no more than 4 to 6 inches below the lights and leave the lights on for 12 to 14 hours a day.  I have a 5-shelf storage rack in my basement outfitted with shop lights, ideal for me since I start multiple flats of seeds at home.  Maintaining proper temperature is also important, a temperature range from 60 to 70 F is ideal. 

Sometimes with indoor seedlings a nutrient deficiency will occur.  Signs include yellow-green foliage indicating a possible nitrogen and phosphorus deficiency or purplish leaves indicating a phosphorus deficiency.  It's a good idea to apply a dilute fertilizer solution once every two weeks to seedlings to help maintain proper nutrients.

If you started seeds in a large container or together in one flat, they should be transplanted into individual pots or cell packs once they grow their first set of "true" leaves.

Share |