14 April 2012

Iris germanica is Bearded Iris

In our garden, several bearded iris colors are showing off their springtime beauty.

This cold-hardy perennial takes little maintenance, usually multiplies over the years, and, if you mix the varieties, you'll have a month of flowers.
The flower itself has three upright petals or standards and three hanging petals or falls. The beard is the fuzzy line in the middle of the fall.
There are sizes for all parts of the garden: Miniature dwarfs are 8 inches tall or smaller, standard dwarf is 8 to 15 inches tall, intermediate is16 to 27 inches, miniature tall 16 to 25 inches with small flowers, border is 16 to 27 inches, and tall ones are 28 to 38 inches.

The best time to plant or divide and renew is after they are finished blooming, July through September, though I've been guilty of moving them when I have time rather than waiting. For example, this spring, while I can see the colors displayed and how I want to re-mix them, I wait until the flowers fade, and move them.

 
By the way, they bloom once the single rhizome you planted becomes a cluster of 3. When transplanting, carefully, discard the center one that bloomed this year and replant the 2 side rhizomes into prepared soil.

Plant at least three rhizomes of the same color, 8 to 10 inches apart, pointing the fan of leaves away from the center. The underground offsets develop from the original rhizome, making a fan of leaves and flower stalks that will bloom next year or the year after.

Iris rhizomes can rot if they are too wet, so sun and good drainage are essential for success.

Annual fertilizer application of bone meal or 5-10-10 is usually recommended. You can just toss fertilizer on them if you water it in thoroughly, but the best advice is to gently scrape the ground around the rhizomes and put it on the soil and water it in.

If your iris disappoint with limited flowers, they may be in too much shade. Giving them too much nitrogen fertilizer will make lots of pretty leaves but few flowers. They will also stop flowering if they need to be divided.

If you find bacterial soft rot dig up the rhizomes, cut off the rot, destroy the diseased parts and replant the remaining rhizome. I would dust with fungicide before replanting.
Rot at the base of the leaf is crown rot fungus. One symptom is red-brown seeds. Trim the leaves to allow more sun and air flow to hit the rhizomes. Destroy the diseased parts.
Streaked, spotted brown leaf spots are bacterial leaf spot. See the Univ. of MN site for more specifics but the basics are: Remove the infected leaves, provide more sun and air circulation.
Fungal leaf spots are rust-colored and more confined. Cut and destroy the leaves and spray plants with fungicide.
Mosaic is a viral disease transmitted by aphids. Remove and destroy infected plants.
If there are small notches on the leaves, there are iris borers present. Apply an insecticide after removing infested leaves. Repeat insecticide application according to product instructions, until the plants recover.

The American Iris Society has several interesting links if you would like to learn more online at
http://www.irises.org/Resources/On-Line_Groups.html

Region 18 of the American Iris Society, in a St. Louis suburb, has quite a bit of information at http://www.region18.com.

While at Longue Vue last month, I saw beds of Louisiana Iris for the first time. If you grow those, here's the Louisiana Iris society web page with tips on success with them.

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