LESS FREQUENTLY ASKED QUESTIONS
scorch and what can I do about it?
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:
What is crown rot, mustard seed fungus, southern blight?
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.
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.
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.
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:
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.
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.
When I hold some leaves up to the light, I see spots inside them--what are they?
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.
What are the accordion-like crinkles on my beardless iris leaves?These harmless decorations are caused by varying growth rates of the inside and outside of the leaf. A rapid growth spurt can cause this differential, or even a sudden warm windy period. Some varieties are more susceptible than others.
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