Blue-green Growth on Tree Worries Homeowner
Finding strange-looking "stuff"ť growing on plants can be alarming. Is it a disease? A parasite? Something that is killing my plant? It is always a good idea to check, but sometimes the stuff turns out to be relatively harmless, albeit unsightly.
QUESTION: "I have this stuff on my tree. It is a blue/blue-green speckled substance that looks like a mold to me. It has been there since summer. The tree is in continuous sun in the backyard, but it gets a lot of water from my neighbor"™s yard, but this stuff is about chest high on the trunk, not near the bottom. I have also seen it on the street trees in the development, which tend to be maple, a few locusts, and one other I am not sure of. Your thoughts?"ť – Kathy
ANSWER: What you describe sounds like lichens. Here's the good news: Although lichens grow on tree bark, they are not parasitic (disease-causing organisms), and do not harm trees, according to the Extension service at the University of Minnesota.
If you wish to be sure it really is lichen, you can find a brief description of tree lichen and a photo at their Web site. Go to http://www.extension.umn.edu/ and type "śtree lichens"ť in the search window.
For the scientifically minded, the U of M page tells us that lichens are organisms consisting of a fungus and a green or blue-green alga that have grown together. Here"™s another bit of good news regarding your immediate environment, if you see lichen on your trees: they are an indication that the air nearby is relatively pure. Most lichens will not grow in a smoky or polluted atmosphere. So, if you see lichen you can breathe easily for more than one reason.
As a footnote, a few days later, I received the following e-mail from Kathy:
"That's it exactly! Looks just like it. Even mentions my tree growing in full sunlight. I"™m glad to hear that I am not going to lose it. Thank you."ť
QUESTION: "I recently purchased a Japanese Snowball plant. This plant is to replace a customer's plant that I damaged in the process of working. I need to know what kind of care this plant requires and what kind of conditions this plant requires for optimum growth. Any information that you can give concerning this specific plant would be greatly appreciated."ť – Richard Z.
ANSWER: For basic information about planting container and bare root shrubs, you can read a useful guide written by Cheryl (a.k.a. Mrs. Plant Man) here: http://www.greenwoodnursery.com/Documents/Planting_Shrubs.pdf
However, for more specific information on growing Viburnum Japanese Snowball plants, I found a very useful article by Georgia Lund that offers detailed info on planting, pruning, and fertilizing for this plant. Go to www.associatedcontent.com and type "śJapanese Snowball Bush"ť in the search window. If you prefer, you can click on direct links when you find this column at my Web site, www.landsteward.org
QUESTION: "I am trying to determine how close together I can plant Willow Hybrids. I want to achieve a grove effect, much like a grove of river birch, to block my neighbor's unsightly yard when looking out my kitchen window. Any input you can provide would be appreciated."ť – Clayton B.
ANSWER: Willow Hybrids (Salix Alba Matsudunna) can put on significant growth even over the first couple of years after planting. For a continual block, you might consider spacing every 5 to 7 feet apart. This will give you a privacy block within a few short years.
However, do keep in mind, that as these plants grow they can achieve considerable size. In 10 years or so, you may need to remove every other tree to allow more spacing between plants. It might not happen, but it is something to be aware of when initially planting closely. I recommend planting hybrid willows and hybrid poplars an additional 10 to 14 inches deep for stability.
The Plant Man is here to help. Send your questions about trees, shrubs and landscaping to steve@landsteward.org and for resources and additional information, or to subscribe to Steve’s free e-mailed newsletter, visit www.landsteward.org
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