neighborhood
garden for August 20, 2016
time to plant
your and/or divide IRIS
by Gladys jeurink
We need to be planting our
new iris, and/or dividing iris that have been in the ground for three
years or longer, before too late in the fall. The best time to do this
is in August or early September. The iris have been storing up energy
and producing new plants since finishing blooming. Remember, iris are
not water loving plants. As
they get started in the spring, watering is needed, but later they
prefer a full sun, well drained spot. Too much water gives high leaf
growth and too little bloom.
But also remember, they are not a desert plant. Too hot a sun all day
fades their blooms.
Much of
Lincoln’s soil suits iris as they like a soil neutral or slightly acid.
A goodly amount of compost in the soil is desired, but too much
compost will retain a lot of moisture longer and encourage root rot.
If you use manure, dig it in deeply after decomposing so that it
will be below the rhizomes.
They are not heavy feeders, as too much nitrogen promotes foliage
instead of flowers.
Now that their
new soil is ready, dig or buy your new plants. When digging and dividing
existing iris, I like to cut the fans (leaves) back to about 6-8 inches
(so that the roots don’t have too much to support) and divide the roots.
I like to make a hole about 4 inches deep and 6 inches wide.
I hold the rhizomes at the top of the hole so that it will be
barely covered with soil when I’m finished.
Sometimes, I even leave them showing a little. Then, I take the
roots and spread them out and down and fill in the soil over them. They
will need to be watered several times to settle the dirt closely around
the roots. Growth is from the front and sides so you can plant them to
grow in the direction you would like.
How far apart?
That depends on how soon you want to transplant them.
I like at least 2 feet between clumps and even then by 3 years
they are crowded. The
tighter the crowding the poorer the bloom crop will be. Also, if you
wait and plant too late in the fall so the roots don’t get established,
freezing and thawing will heave the plants out of the ground.
Before you
plant your new iris or the ones you just divided, check for disease and
insects. Here in Lincoln we
are favored by borers. Look
for their tunnels and also the borers as they are helpers of root rot.
For disease control and to drown any borers and insects, I make a
solution of one part chlorine (bleach) to nine parts water in an old
wash tub and soak the rhizomes not more than an hour or two. The insects
and borers will float to the top. Any plastic bucket or other container
will work fine. Soaking for even a half hour will kill the insects,
borers, and disease. The easiest is to clean the dirt from any plants
dug up; throw out any plants that are mushy from disease, rot, or
borers; divide the rhizomes as needed; and then put them into the
solution until you are finished. Let the rhizomes dry in the sun before
planting.
Borers lay
their eggs in the fall on the old foliage, giving us a very good reason
to clean up all old foliage in late fall or very early spring.
Bob Gilmour, a Master Gardener, used to put Bordeaux powder on
his plants after cleaning up the bed in the fall, and then again in the
spring as growth begins.
Bordeaux is an organic copper fungicide.
As iris grow,
the mother plant will die out and leave a dead spot in the middle with
daughters all around. In
time the whole bed will be crowded with the daughters, and the blooms
will be smaller as it is those daughter plants that produce the new
flowers. Check your iris bed
now and see if it needs to be divided.
Remember, the best time to plant new iris or dig up and divide
old iris is August and early September so now is the time to get
started. Copyright 2016
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