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The Passionate Gardener for March 18, 2010

by Karyn Ames

Master Gardener

New Mexico Certified Nursery Professional

    If you have started planting some of your seeds, by now they might be coming up.  The next stage of seedling development is called “growing on.”

    Seedlings no longer need the high temperatures and humidity they needed for germination and now do best at 60 to 65 degrees F, temperatures similar to fine spring days.  If you have plastic or clear domes over your seedlings, remove the plastic as soon as green shoots come up.   Extra humidity and heat can encourage damping-off, which is a fungal disease that can kill the seedlings overnight.  The fungus rots the stems at the soil surface and causes the seedlings to fall over and die.  So, air circulation is vital to your seedlings.

    If you do have some seedlings succumb to damping-off, do not try to save them.  It is early enough in the year so that you can start new seeds.  Do not reuse the contaminated soil; the compost bin will welcome it.

    Careful watering is crucial at this time.  Too much water applied too fast can drown the seedlings.  At this stage I use a spray bottle with a fine mist, because even the finest setting on a hose sprayer can be too forceful.  If my seedling tray has dried out so that misting does not do the job, I place my tray of cell-packs into a basin of water to let the moisture soak up from the bottom through osmosis into the soil.

    Seedlings need 12 to 18 hours of light each day.  This may seem excessive, but the low rays of the winter sun and artificial lights are not as intense as full summer sun.  Lamp timers will help immensely in this chore of keeping the seedlings basking in a regular light schedule.

    Next time I will discuss fertilizing and thinning your seedlings.