Fall into Trees!

Oct 08, 2008

Do you know when the best time to plant trees is? It's Fall! Fall temperatures and frequent rainfall make it the perfect season for planting trees. One of the most common questions asked at this time of year is "what type of tree should I plant in my yard?" There are several possible answers to that question depending on whether you want shade trees, trees that grow fast, trees that are less likely to be hit by lightning, or possibly have the prettiest colors in the fall.

Please note that we are not recommending any particular type of tree. We are merely presenting information to answer some of the more popular questions we receive about trees.

Fast Growing Trees

Factual information on how fast specific tree species grow can be difficult to find. Many commercial tree sellers simply list a tree as fast-growing versus slow-growing without giving any more specific information about how many feet per year it may grow. The most recent article available with comparative information across a wide range of tree species was published in 1995. Everyone seems to want a tree that grows fast; however, few stop to realize there can be many problems caused by fast growing trees. According to ISU's Horticulture and Home Pest News from March 24, 1995 - "fast growing trees often have the problem of being weak wooded and break apart quite easily in ice and other types of storms. Thus, a fast growing tree near a home often becomes a hazard."

As explained in the article, growth rates of trees vary depending on variety and a number of environmental factors. The article reported on the results of a 10 year study on growth rates in a controlled environment. They provided the following growth rates for tree species:

Trees rated as fast growing were at least 25 feet tall after 10 years. These included:
American Elm (Ulmus americana)
Silver Maple (Acer saccharinum)
Sycamore (Platanus occidentalis)

Moderately fast growing trees included:
Kentucky Coffeetree (Gymnocladus dioica)
Thornless Honeylocust (Gleditsia triacanthos var. inermis)
Linden (Tilia platyphyllos, T. cordata, T. xeuchlora 'Redmond', and T. tomentosa)
English Oak (Quercus robur)
Pin Oak (Quercus palustris)
Sawtooth Oak (Quercus acutissima)
Shingle Oak (Quercus imbricaria)
Red Maple (Acer rubrum)
Sugar Maple (Acer saccharum)
Tuliptree (Liriodendron tulipifera)

Tough Fast Growing Trees:

The staff at Weekend Gardener at http://www.weekendgardner.net recommend 3 trees that "can take extreme cold, heat, wind, and are fast growing. These trees have also been used for years in the Great Plains as windbreaks."

1. Green Ash (Fraxinus pennsylvanica)
A large tree that grows up to 60 feet tall. It has green leaves that can turn a nice yellow in the fall, but don't count on the color.

2. Box Elder (Acer negundo)
Fast growing to 30 to 50 feet. Has a rounded top.

3. Silver Buffalo Berry (Shepherdia argentea)
Can be grown as a tree or shrub. Has silvery leaves and red or yellow fruit. Grows to 18 feet. (FYI - commercial tree websites often neglect to mention this tree has thorns.)

It should be noted here that Green Ash (as well as other native Ash species) are not recommended for planting in Iowa at this time due to the Emerald Ash Borer. The closest infestation of this insect was reported in Illinois, but could easily spread into Iowa. For more information see the announcement from ISU Extension News: http://www.extension.iastate.edu/news/2008/jul/422301.htm

Trees struck by lightning most often?

The last thing you want is to plant a tree and then discover it's more prone to be struck by lightning. The debate is still raging over exactly which trees are the most susceptible to lightning strikes and why, but here are some of the more popular suggestions and reasons.

"Replies were compiled from many different sources and showed the following number of lightning strikes:oak, 484; poplar, 284; willow, 87; elm, 66; pine, 54; yew, 50; beech, 39; ash, 33; pear, 30; walnut, 22; lime, 16; cherry, 12; chestnut, 11; larch, 11; maple, 11; birch, 9; apple, 7; alder, 6; mountain ash, 2; and hawthorn, 1. Only after further prompting from the editor did one reader admit to seeing a stricken sycamore. There were assertions that holly was never seen to be hit."

Some arguments seem to favor the height of the tree being a relevant factor while others seem to favor the moisture content of the bark. "Trees with corrugated bark (and therefore traces of moisture) attracted more strikes than those with smooth bark... This would explain why beech, with its smooth bark, is less susceptible to strikes."

The problem with this line of inquiry is that unless a tree was damaged by the lightning it can be difficult to tell whether or not a specific tree was hit. A definitive answer will be hard to come by as it is almost impossible to construct a series of tests with even conditions across a wide variety of trees.

Quotes taken from "The Last Word," New Scientist, v. 166, no. 2242 (Sept. 9, 2000), page 109.

Best trees to plant for fall color?

Check out About.com's Landscaping Guide at:

David Beaulieu gives an overview of his planting choices and provides links to more detailed information on each of these: Quaking Aspen, Beech, Birch, Dogwood, Japanese Maples, Oaks, and Sumac. Please note that his article does not mention anything specific to the Midwest or Iowa. He also recommends several ash trees but, as noted above, ash trees are not recommended for Iowa right now.

Fall Color in Iowa
ISU Forestry Extension staff provides a list of leaf color characteristics of various trees in Iowa along with a basic explanation of why leaves turn color. Plants they mention include:Walnut, Red Oak, White Oak, Bur Oak, Hickory, elms, soft maple, hard maple, Sumac, and Virginia creeper. This page is not very current, but it is one of the few to mention Sumac and Virginia creeper colors.

Please note that the Iowa DNR Forestry Bureau updates Fall Colors in Iowa each week starting in Mid Sept on their web site http://www.iowadnr.gov/forestry/fallcolor.html and also has a Fall Colors Hotline that is updated once a week - 515-233-4110

Looking for more information on a specific tree?
The Parks Library has a large variety of books about trees, including identification guides and encyclopedias (many with gorgeous color illustrations) located on the Lower Level at call number QK 481. If you would rather browse resources on the Internet - give the following a try:

PLANTS Database

Tree Guide at arborday.org
Entries give information on height and spread, soil and sun requirements, leaves and fruit, history, wildlife habitat, growth rates, and more.

Trees and Shrubs of the Campus of Iowa State University
Contains descriptions of 100 large plant species found on the ISU campus, including bark, leaf, habitat, and use characteristics.

UIPLANTS database
UI Plants is a database on woody landscape plant identification, culture and usage for the Midwest, including native and introduced species. Links on the right side of the page provide additional plant details - including fall color.

Talk to an expert!

There are a number of other things to consider when planting a tree - not just the types of things that were mentioned above.Take a look through the links provided by ISU Extension at:

Still have questions? Contact the ISU HortLine to talk about your particular planting situation and get more specific information. They will not tell you what to plant, but they will make sure you have enough information to make an informed decision for your yard. They accept queries via email or phone: