University of Vermont Extension 
Department of Plant and Soil Science

Fall News Article
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DIVIDING IRIS AND OTHER SEPTEMBER GARDENING TIPS
 
Charlie Nardozzi, Horticulturist and
Leonard Perry, UVM Extension Horticulturist
 
 
Bringing houseplants indoors, cleaning up annual flower beds, and dividing iris are some of the gardening tips for this month.

Ready houseplants for winter by checking them for insects, trimming off dead foliage and stems, and repotting if necessary.  Don’t use garden soil, but rather a mix formulated for potting houseplants.  This usually doesn’t have soil, but is “soilless” having peat moss, vermiculite, perlite, or other such ingredients.  Garden soil doesn’t have good properties when put in a pot, and unless pasteurized may introduce diseases and insects.  Gradually move houseplants into shadier conditions to get them used to less sunlight before bringing them inside when nights dip into the 40s.

As you empty annual beds this fall, there are two main ways to enrich the soil for next year: spreading compost or planting cover crops. Before you spread compost, dig or lightly till in any plants that aren't diseased to return nutrients to the soil. Spread compost, even if it's not well decomposed yet. It will protect the soil over the winter and break down by spring planting time. Or you can plant cover crops, such as buckwheat or annual rye that will grow this fall and early spring until you till it under several weeks before planting.

Lift iris clumps with a shovel and break them apart. Save the plumpest, firmest rhizomes, and discard the old, leafless ones. Trim the leaves to about 6 inches long. Let the rhizomes air dry overnight before planting. Check to make sure they aren’t mushy—a sign of the iris borer. Break off and discard in the trash (not the compost) infected rhizomes.

Daylilies can go years without dividing, but if they’ve gotten too large or aren’t blooming well, early fall is a good time to divide.  Daylily clumps are so dense you'll need to slice through them with a shovel or spade. Separate them into smaller clumps, leaving at least three plants per clump. Trim leaves to about 6 inches long and replant in a soil enriched with compost.  Water well, and give some liquid fertilizer.  This will help them get established before winter.

Get those weeds out of your garden or else they will make it doubly hard for you next spring. Since bare soil invites weeds, cover bare soil with mulch, such as layers of wet newspaper covered with straw, compost, or manure. This will control late fall and early spring weed growth and provide organic matter.

Japanese beetle larvae have burrowed into the soil, so it's a good time to treat the soil with beneficial nematodes. These microscopic "roundworms" enter the larvae and kill them with bacteria they release, which in turn convert grub tissue to nutrients for the nematodes. If you can't find these beneficial nematodes at a local garden center, check online for a mail-order source.

There's still plenty of time to plant trees and shrubs and perennials, and the prices are right. Root growth will continue into late fall or early winter, and plants won't have the heat of spring or summer to dry them out. Be sure to water well at planting time and every week until they go dormant.  Wait to fertilize until spring, otherwise new growth may sprout that wont be winter hardy. 

(Charlie Nardozzi is a nationally known horticulturist, author, gardening consultant, and garden coach; CharlieNardozzi.com). 

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