University of Vermont Extension
Department of Plant and Soil Science
Fall News
Article
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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