How to Grow Bearded Iris

Iris come in a rainbow of colors, and they’re

one of the easiest perennials to grow. With a

minimum of care they will reward you with

beautiful blooms year after year. Follow a few

simple steps and you’ll be a successful iris

grower.

When to Plant
 
 

For best results, iris should be planted in July,

August or September. It’s imperative that the

roots of newly planted iris be well established

before the growing season ends.

 

 

Where to Plant
 

Iris need at least a half day of sun. In

extremely hot climates some shade is beneficial,

but in most places iris do best in full sun. Be sure

to provide you iris good drainage, planting either

on a slope or in raised beds.

Soil Preparation
 

Iris will thrive in most well-drained garden

soils. Planting on a slope or in raised beds helps

ensure good drainage. If your soil is heavy,

compost or humus may be added to improve

drainage.

The ideal pH is 6.8 (slightly acidic), but iris

are tolerant in this regard. To adjust the pH of

your soil, lime may be added to acidic soils or

sulfur to alkaline ones. It is always best to have

your soil analyzed before taking corrective

measures.

While preparing your soil, soak iris in water

for 10-15 minutes to reconstitute the roots and

rhizome.

Depth to Plant
 

Iris should be planted so the tops of the

rhizomes are exposed and the roots are spread out

facing downward in the soil. Firm the soil around

each rhizome and then water to help

settle the soil. A common mistake is to plant iris

too deeply.

Watering
 

Newly set plants need moisture to help their

root systems become established. Specific

watering information depends on your climate

and your soil, but keep in mind that deep watering

at long intervals is better than more frequent

shallow watering. Once established, iris normally

don’t need to be watered except in extreme

drought conditions. Over watering is a common

error. Re-blooming iris do require a little extra

watering during the summer, however, to produce

their fall blooms.

Fertilization
 

Specific fertilizer recommendations depend on

your soil type, but bone meal, super phosphate

and 6-10-10 are all effective. A light application

at planting, again in the early spring and a second

application about a month after bloom will reward

you with good growth and blooms. Avoid using

anything high in nitrogen, as nitrogen encourages

rot problems.

Thinning Old Clumps
 

Iris need to be thinned or divided before they

become over crowded, generally every 3-4 years.

If iris are allowed to become too crowded the

bloom will suffer, some varieties may crowd

others out and disease problems may be

aggravated. Dig up the entire clump, separate the

rhizomes (removing any diseased or damaged

ones) and replant them as soon as possible.

Distance Apart
 

Iris are generally planted 12-24 inches apart.

Close planting gives an immediate effect, but

closely planted iris will need to be thinned often.

Plants spaced further apart will need less frequent

dividing.

General Garden Care
 

Keep your iris beds clean and free of weeds

and debris, allowing the tops of the rhizomes to

bask in the sun. Bloom stems should be cut off

close to the ground after blooming. Healthy

green leaves should be left undisturbed, but

diseased or brown leaves should be removed.

Kansas State University Gardens

1500 Denison Avenue

Manhattan, KS 66506

fhis2014@gmail.com

Tel: 785-532-3271

© 2023 by Alison Knight. Proudly created with Wix.com