Home Page

Thanks Billie Gray for an informative overview of iris culture.  Her first bit of advice was on choosing iris from a catalog, "do not just depend on the photograph; read the description, too".  The advantage of buying your iris locally is they are acclimatized.  Many iris out of our area are better off to age first before planting (let them sit and dry) until new roots show and they become hardened off.  Choose nice, fat firm rhizomes.

When choosing a location to plant, remember large iris rhizomes need a lot of sun and good drainage.  When planting, trim off old shriveled leaves and trim roots with scissors.  Make a mound, drape roots over mound and pull soil up.  Leave the top of the rhizome barely exposed to the sun; do not plant deep.  Spacing is best at 12"-24" apart.  Try to get three of the same variety and plant them in a triangle together.

Water well in the Spring and after planting, then let dry off for about six weeks.  In the summer, they do like to dry out between watering, then in August and September resume plenty of water again. It is best to water early in the day, so plants dry out during the day. However, Japanese Iris do not like to dry out.

You should have continuous bloom each year, if you follow a division program every 3-4 years.  When you divide, discard the center with the bloom stalk (mother rhizome) because it will not bloom again.  The two on each side are the ones that will provide the bloom next year.

When cleaning the iris in the Fall or Spring, old leaves can be taken off by cutting or pulling.  However, a word of caution. Tearing an iris can release toxins.  If you tear, wait until Spring when leaves are dead.   Do not injure the rhizome, as any cut or injury will allow bacteria to enter and start to rot. Be careful when you are weeding, too.

Low nitrogen fertilizers are best, including bone meal and phosphorus.  Feed iris early in the Spring and again after bloom.  A 5-10-10 once a year is good, too.  Something like Osmocote pellets or another timed release fertilizer with a high middle number as a top dressing.  Iris respond well to Epsom Salts, about 2 tablespoons around each plant in the Spring. 

As far as insect attacks, we don't have a lot of problems in our climates.  Borers are rare, some aphids and some thrips but sprays such as insecticidal soap will help control this.  She didn't mention deer, but I find an occasional chomp from them.

Rot and leaf spot are more bothersome for our area, mostly because tall bearded (TB's} don't like wet feet or overhead sprinkling.  If you do find rot in a rhizome, take it out.  You can destroy the rotted rhizome and save the increases on the side; the white roots at the back or heel are the productive ones.  Cut the rot with a clean knife, not serrated.  Don't replant right away; instead let it ripen or callus for a few days first.  Do not leave it on the ground where it will get watered.  It's better not to replant in the same space.  If you do want to replant in the same space, remove some soil and add fresh soil.  Treat a fungus with two unbuffered aspirin tablets per gallon of water.

Leaf spot is a series of blotchy spots on the leaves.  This infection is splashed on the plants from overhead watering, because it harbors in the soil.  If lesions are severe, you may need to cut the plant all the way down.  You can treat it with a copper sulphate, Bordeax mix.  Pea gravel around the plants, about 3" deep, can help prevent organic material from causing the disease.  The pea gravel also prevents heaving in the winter.