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Enterprise readers ask about changing flower colors

Enterprise readers asked if these pale yellow irises would come back some year in a completely different hue. (Sarah Smith / Enterprise)

Q. Enterprise readers have told us that sometimes perennials come back in a different color. One woman talked about yellow irises coming back pale blue one year. Another has said delphiniums changed color from year to year. A third said tiger lilies did the same thing. Are these old wives tales or does this happen? Do perennials change color as they age?

A. Generally, no. What happens is that many reseed the area and what comes up is not the mother plant, but seedlings from that plant, which are of differing colors. If a rhizome plant like the iris changes color it is considered a mutation or a chimera (sport). If the plant was grafted, it could be that the grafted scion has died out, and the rootstock has taken over. This is most common on roses. Environmental stress can also change flower color - For example, stress occurs when a plant is moved from one place to another and the result is that the flower can actually change colors.

If a purple iris is transplanted and in the process is left out of the ground too long, when it blooms in the spring it may be white. Finally, as plants age, their flower color could change. This would be like our hair going from red, brown, or black, to gray as we get older.

Color changes can occur in flowers based on the pH of the soil, but this is usually not common nor a radical shift in color.

Q: I live in north Fargo on a typical city lot. I miss the fruit trees I had when I lived in zone 6. I would like to grow fruit. However, I don't have room for two each of apricot, pear or plum trees. Can I use a bush apricot, sand plum or some other type of bush for cross-pollination? Is there a variety of cherry that will produce up here? Would it require a cross-pollinator?

A: Are you living in an isolated location away from neighbors and other landscape plantings? I'd bet not, so I am willing to say that somewhere within a quarter of a mile radius are plenty of similar trees that can serve as cross-pollinators. The only exception might be pears because they suffer from iron chlorosis and fire blight problems in our area.

Q: I have two houseplants with mold problems. One has yellowish mold, while the other has whitish mold in the soil. Both plants seem healthy and neither seems to have mold on the plant. I thought I'd killed off the yellow mold awhile back by letting the plant dry almost completely (it's a tough little hoya). I repotted it last year and the mold returned with a vengeance. Can you recommend a good fungicide to put in the soil of these plants? I worry the mold may spread to my African violets.

A: This is a saprophyte problem, not a parasite. It is working on digesting the organic matter in the potting soil. This is nothing to worry about from the plant's point of view. If you are concerned, repot the plants again using a new or clean pot and heat your potting soil in a microwave for about four minutes to pasteurize everything that is in the media.

Q: I have a large eastern cottonwood in my backyard. I love this tree because it provides a lot of shade for my house. About two months ago, big pieces of bark started falling off the upper branches. Some branches are pretty big. I called a local tree and turf adviser who said the tree had borers and larvae. He recommended removing the tree and nothing else. About half the tree is still alive. I would like to save the tree, so is there any way to spray for this problem? If the tree is removed, will these borers move to my other cottonwood and pine trees?

A: A half-dead tree is not something you want to try to save, especially one that is infested with borer larvae. Get the tree removed as soon as possible by a qualified, insured and bonded tree expert. At the same time, have the surrounding trees checked for insect infestations so that remedial action can be taken before it gets too late as it is with your cottonwood tree. I wouldn't waste any time. I don't mean to scare you, but the possibility of a large tree falling and damaging your house or a loved one isn't worth debating.

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail