LESS FREQUENTLY ASKED QUESTIONS

What is scorch and what can I do about it?
What is crown rot, mustard seed, botrytis, southern blight?
What else can I do to battle bacterial soft rot?
Will Louisiana irises grow in the north?
What's the best way to remove stalks?
Why do violet-blue irises look violet in my photos?
What made my irises' colors revert?
Can Spuria irises do well where summers are wet?
Do I need to move my Japanese Irises often?
Do deer eat irises?
When I hold some leaves up to the light, I see spots inside them--what are they?
What are the accordion-like crinkles on my beardlless iris leaves?

What is scorch and what can I do about it?

Scorch is a set of symptoms that is generally fatal to at least the fan that is attacked. It is characterized by leaves turning yellow, orange, or brown at the tip and that browning continuing down toward the rhizome. A very rough diagnostic tip: When you see the top of a leaf in the center of the fan turning brown, give it a little tug; if it comes out, you have bacterial soft rot, and if it doesn't, you have scorch. Scorch's cause is uncertain, but its onset may be associated with an as yet unidentified insect.

One approach to dealing with it is essentially one of containment. When the problem first appears, cut the rhizomes in the clump apart. That way, the problem will not spread from one affected fan to others. These cuts can be made while the plant is still in the ground.

Bill Burleson provided the following information on a treatment:

Reliable research (University of Iowa Botany Dept.) suggests that holding the rhizome at a temperature of a 104 degrees F. for 72 to 96 hours (3 to 4 days) will cure the plant. This same research claims 100% success rate in curing the disease. As a practical matter I use the following approach. I use an accurate thermometer (medical type) or sometimes use a digital type with a remote sensor that stores the maximum and minimum temperatures. I use a dry fish aquarium covered with plate glass but a gallon jar would work fine. Generally, I clean the rhizomes by shaking off the dirt and don't wash it. But, if circumstances dictate that it be washed (clinging muddy soil attached when dug), I wash and allow it to sun dry prior to placing in the chamber. Place the rhizome in the chamber (jar). Place the thermometer in the chamber in a position you can easily observe temperature and remove it to shake down if necessary. Place chamber in the sun and periodically observe the temp. My maximum temperature has run as high as 110 degrees for brief periods with no ill effects. I regulate the temperature by adjusting the opening in the cover of the chamber or by moving the chamber to a cooler location. I allow the rhizomes to remain in the chamber for a week or so. When they come out, I replant, often in the same spot. The problem does not reoccur. I've only had a few instances of scorch to practice on but this method has worked 100%! A somewhat faster, more precise, but more expensive suggestion is to use an incubator or a food dehydrator.

This often appears as a dark gray mass over the rhizomes and nearby areas. Leaves will often yellow and fall over as well. It is caused by a fungus, Sclerotium rolfsii, not a bacteria, like soft rot, and so if you are inclined toward chemical controls, something like a Terachlor drench may work best. Always, though, clean out affected tissue, expose rhizomes to the sun, and do your best to provide weather that is not hot and moist.

What else can I do to battle bacterial soft rot?

Besides all of the main things to do--providing good drainage and aeration, selecting good varieties, avoiding over fertilization--you can take a few measures when rot does appear. Dial liquid antibacterial soap (or another with triclosan) can be helpful. In addition, some growers have used insecticides like Sevin on the theory that insects spread rot from plant to plant.

Will Louisiana irises grow in the north?

Yes, many will, at least as far north as South Dakota. Some species within the Louisiana set are more hardy than others. To give yourself the best chances, choose initially ones that have been bred for cold climates, such as, for example, some of the Morgan hybrids.

What's the best way to remove stalks?

The crucial elments of stalk removal are to do it near the ground and on a dry day. Beyond that, Bill Shear suggests that it is much better to break the stalk than to cut it. When a break occurs, it is much more likely to take place at cell boundaries, which is better for the plant. Properly dry stalks can usually be snapped off by grasping them near the base and bending them against the direction of growth. Occasionally a little twist and pull is necessary, but, if so, use your other hand to steady the rhizome so that your pulling does not disturb the roots, or pull up the plant.

Why do violet-blue irises look violet in my photos?

You are experiencing the "ageratum effect." Iris pigments, like many flower pigments, reflect a variety of colors of light. Your violet-blue irises reflect violet-blue light, and they also reflect some infrared light that is beyond the spectrum your eyes can see. Some irises are better examples of the problem than others--Siberian iris JAYBIRD, for example, seems more resistant to the effect than others. Most photographic films and some digital CCDs, though, are sensitive to portions of the infrared spectrum, and it renders that light as red on the finished picture. This red is what makes your iris look violet instead of violet-blue.

Solving the problem is extremely difficult. There are infrared filters that work, but using them requires so much light that photography the necessary tradeoffs in film speed, aperature and exposure time make photography challenging. Most people instead "cheat" by using darkroom alterations or computer alterations to render the flower accurately when that is the main point of the picture, even though other elements of the picture will be somewhat distorted. Some digital cameras have been developed with less sensitivity in the infrared region, and those are certainly worth a try.

What made my irises' colors revert?

Every once in a while, a casual grower reports that a clump, a bed, or a field of irises has "reverted" to another color, often white. There may be different things going on in different cases. Here are some of the leading contenders:

• Herbicide has drifted onto the bed. Several herbicides cause damage and discoloration to irises. Roundup will often turn irises white and can deform flowers. In many cases the plants will return to near-normal if no new herbicide is applied for a year.
• Over the years, a stronger variety has crowded out a weaker one. This can happen even if only a few bits of the stronger one were left.
• Seeds were dropped from the varieties grown and the plants eventually grew strong.
• Mutations and sports do, of course, occur, but these are very rare, and it is extremely unlikely that they could happen to more than one plant in close proximity.

Can Spuria irises do well where summers are wet?

Do I need to move my Japanese irises frequently?

Probably. Japanese irises emit a toxin from their roots. That toxin builds up to effective levels after three to five years, and it then inhibits the growth of Japanese and many other irises (apparently not daylilies, though) from that soil for several years. Growers of JIs who have them located near moving water seem to suffer no ill effects.

Solutions are to move the irises frequently from area to area, or, probably best, grow the JIs in pots, as the Japanese have done for centuries.

Do deer eat irises?

Yes. Although many lists of plants not favored by deer include irises, this in many cases represents a preference. As deer are hungrier, they will eat some of those plants that are not their first choice. In addition, gourmet deer have been found in increasing numbers; these deer, of course, prefer irises, sometimes specific ones as their palates mature.

Many anti-deer tricks have been tried, some with success until it rains, etc. A product like This One Works has somewhat greater durability, but the most reliable way to deter deer is to build a high double fence.

The spots (or dashes that are perpendicular to the direction of the leaf) are water marks, possessed by many true water irises. I. pseudacorus has the best, but other water species do too in varying degrees.