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How to Dig, Divide, and
Transplant Bearded Iris |
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By Laurie Frazer
The
Irises at Shadowood |
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Bearded irises can be
divided any time after
your last frost date in
the spring, but many
irisarians believe the
optimal time to divide
them is 6-8 weeks after
bloom. Avoid
transplanting irises in
very hot weather (90+ F
degrees), but do get
them transplanted back
into the ground a couple
months before freezing
weather to give them
time to root in well
before winter. Irises
sometimes take a year
off bloom after
transplantation to
settle into their new
homes, so don't be too
disappointed if you
don't get bloom the
spring after planting.
Irises moved before
bloom will often lose
their bloom that season
as well, which is why
it's best to wait until
after bloom to dig and
divide. |
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Use a
spade or fork to dig up
your iris clumps and
wash them off well with
a hose until you have
removed all dirt and can
easily see where the
rhizomes are attached to
one another. With a
sharp knife, cut through
the attachments (you can
break them apart with
your hands, but a sharp
knife will make a
smaller, cleaner wound).
Inspect the rhizomes
thoroughly. Discard any
rhizomes that are soft
or mushy or show any
other signs of disease,
any that do not have
viable roots, and any
that are just too tiny
to bother with. Many
people also discard old
"mother" rhizomes that
have already bloomed
because they will not
bloom again. These
"mothers" may grow
additional
rhizomes (increases)
however, so they may be
worth replanting if you
have the extra room for
them. Remove any dead,
spotted, or unhealthy
(brown or yellow) leaves
or parts of leaves. Many
folks cut the leaf fan
back a bit when
transplanting so the
weight of the leaves
won't cause the newly
planted iris to tip
over, but you should
leave as much leaf on
the plant as possible
to continue to
feed the rhizome. Snap
or cut spent bloomstalks
off at the rhizome. Snip
off any dead roots but I
leave the plump roots
intact. |
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If you
find soft, mushy spots
(bacterial soft rot) in
your rhizomes, either
discard those rhizomes
in the trash (do NOT
compost), or cut the
mushy parts out. If you
do decide to keep
otherwise valuable but
rot-infected rhizomes,
soak them in a solution
of 1 part household
bleach to 9 parts in
water for 30 minutes,
then rinse in clear
water. |
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After you
have separated,
inspected, and cleaned
up your rhizomes, lay
all of them out in a
shady, dry area for a
couple days to allow the
cut wounds to scab over
before transplanting. |
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You
should transplant these
irises into an area
providing at least 6 hrs
of direct sunlight a
day. Prepare a new
planting area or
rejuvenate an existing
bed by making sure the
soil is well-drained and
properly fertilized.
Though iris gardeners
often dig a bit of
superphosphate into the
soil to feed the
rhizomes and help
promote future bloom,
it's actually a wiser
tactic to fertilize
according to the needs
of your particular soil.
This can be determined
through a soil test
performed by your county
extension agent. Avoid
high nitrogen
fertilizers. Excessive
nitrogen can promote
bacterial soft rot in
bearded irises. |
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When you
plant your irises, make
sure the top surface of
the rhizome is level
with or just slightly
below the soil surface.
If you bury the rhizome
too deeply, the plant
may refuse to flower. Do
NOT mulch directly over
the rhizomes. Mulch will
tend to retain too much
soil moisture right
around the rhizomes and
promote bacterial soft
rot (unless you live in
a hot desert climate).
If you have the room,
plant your rhizomes
about 2 feet apart with
no other plants nearby
to overgrow them and
compete for soil
nutrients. You can also
plant 3 separate
rhizomes in a triangle 1
foot apart with the leaf
fans facing outwards to
produce an instant clump
effect. Water the irises
deeply once a week for
the first month if there
is not adequate
rainfall. Avoid
frequent, shallow
waterings. Overwatering
is another common cause
of soft rot problems. |
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Just so
you understand how the
bearded iris life cycle
progresses - each
individual rhizome will
only produce one flower
stalk during its
lifetime. After (and
sometimes before) it
flowers, it will turn
its energy toward
producing "increases"
(new rhizomes growing
from the sides of the
"mother" rhizome). After
these new rhizomes grow
to blooming size and
eventually flower, they
will then become
"mothers" and grow
increases of their own.
That is how single
rhizomes turn into
clumps over the course
of a few years and why
they need to be divided
when the clumps become
overcrowded and deplete
soil nutrients. |
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