Bearded Iris Culture
Prepare a soil bed that is friable at least 10" deep. Place the rhizome
just beneath the surface with the roots spread out and deeper than the
rhizome. Soil should be neutral to slightly alkaline.
DEPTH TO PLANT: Place your rhizomes just below the surface of the ground
with the roots well spread out underneath so the rhizome is within reach
of the warmth of the sun's rays while the roots beneath are in moist
(not soggy) soil. Be sure to firm the soil lightly around each rhizome
when planting. (See figure.)
DISTANCE APART: Depends on your particular plans. Generally Iris are
planted from 8 inches to 2 feet apart. (See figure.) Planting three of
one kind in a triangle, single rhizomes 8-15" apart with the fans
pointing outward, will create a massed effect but will need to be
divided every 2 years. If the plants are set about 2 feet apart they
will need dividing only every third or fourth year. The best planting
time is July through September in the Northwest area. When dividing, dig
the plant, remove and discard the old center rhizomes and replant the
new fans. You may cut out the old centers with a knife while they are in
the ground if you do not wish to lift the plant.
Care of the plants is relatively simple. Keep weeds and grass tufts out
of the rhizome clumps. Cultivate shallowly, since the feeder roots are
near the surface. Newly-set plants should be kept moist until the roots
are growing well. Established plants rarely need watering except during
prolonged dry spells; at such times, deep, infrequent watering is best.
Fertilizer should be applied as a side dressing in early spring, and
then again after bloom. It can burn rhizomes, so apply it around, but
not on, the plant. Too much nitrogen promotes soft, lush growth which is
susceptible to rot, so a 5-10-10, super phosphate or similar formula is
Air circulation and sanitation are the best problem preventatives.
Remove old iris leaves and other debris from around the base of the
plant. Aphids, caterpillars, etc. may damage the flowers, but rarely do
serious harm to the plant. Slugs love to nibble at new shoots and will
even climb and attack the tall leaves of some varieties. Old bloom
stalks should be cut or broken off at ground level - but healthy, green
foliage should NOT be cut off. It needs to be left on the plant to
foster development of new sprouts for the next season.
During the growing season, the plants may be sprayed, along with roses
and other perennials, with a combination insecticide-fungicide spray at
regular intervals - usually 10 days to 2 weeks. In some years, usually
warm, wet ones, leaf spot can make the leaves unsightly. Cutting off the
spotted leaves will improve the appearance of the garden and retard the
spread of disease.
Mulching of bearded iris is to be avoided. If you desire to mulch, do
not cover the rhizomes. The sun must reach them to facilitate
development of next year's increase. Freezing weather will not harm the
rhizomes, other than causing slight "heaving" out of the ground. If this
occurs, simply cover the exposed roots with additional soil.