Homegrown: Tips for houseplants

Linn County Extension Master Gardener, Lisa Slattery, offers timely tips for houseplants:

It's time to prep your houseplants for the coming growing season.  It's still too cold to move them outside but March is a good time to start fertilizing them using a good quality all purpose water-soluble fertilizer. 

If you're like me, I brought in several plants from my yard to winter-over inside and I plan to propagate these for more plants. Because you can never have too many plants, right?

My favorite way to propagate is by cutting slips of the new growth on my houseplants and placing them in a rooting medium.  In a few weeks (about the time it's warm enough outdoors) they'll be rooted and ready to be potted.  Some plants root easier than others.  I root all my coleus in water while I root other houseplant slips, including my favorite passion plant in root growing medium.  

There are some tropical houseplants like the common rubber plant, fiddle-leaf fig, dumb cane (Dieffenbachia), croton, and corn plant (Dracaena spp.) that don't propagate well from cuttings.  A technique called air layering works well for these and helps to rejuvenate plants that have become tall and leggy.  Air layering induces roots to form on a plant stem while it's still attached to the parent plant.  The science behind this is that it works to partially girdle the plant stem so the nutrients accumulate at the point of injury and roots begin to grow.  Ok, so how do you do this?

Air layering is done by first cutting the stem with a slanting cut to a depth of about one-fourth to one-third of the stem's diameter.  Don't cut through the stem.  Hold onto the plant above the cut so that it doesn't topple over and break at the cut.  Place a small piece of wood, like a toothpick, inside the wound to prevent it from healing over.  I'd suggest also adding rooting hormone to the cut area which will speed root growth.  You'll find this at garden centers.  Then grab a few handfuls of sphagnum moss, soak it with water, squeezing out the excess water and make it into a tight ball.  Wrap the moss ball around the cut area on the stem and wrap tightly with plastic wrap.  Make sure the moss isn't sticking out.  Use twist ties or cotton cord to secure both the top and bottom ends of the plastic snugly to the plant stem. 

Check the sphagnum ball every 7 to 10 days for water.  If it turns light tan in color, it needs water, which you can do by untying the top of the plastic wrap and watering.  Look for roots as well.  Some plants will begin to root within 30 days while others may take up to 6 months.  When you have good root development the newly rooted plant portion is ready to be potted.  Cut off the newly rooted plant just below the mass of roots and pot.  If you'd like step-by-step instructions on how air layer houseplants visit the ISU extension website and enter

http://www.extension.iastate.edu/Publications/PM268.pdf .