Tree Notes is about trees -- especially native trees, trees for wildlife, and trees in history.

Thursday, June 28, 2007

Kudzu at Natchez Trace State Park in western Tennessee

Erosion control gone bad

Kudzu at Natchez Trace State Park, TennesseeKudzu vines at Natchez Trace State Park

Kudzu is an aggressive, fast-growing, invasive vine from Japan. It's a big problem in the woodlands of the southern United States, where it completely overgrows native trees, shrubs, and plants, depriving them of sunlight and weighing them down.

Established stands of kudzu are very difficult to eradicate because roots can be 12 feet deep! In some areas, it has become resistant to the herbicides that have been used on it. It can grow up to a foot per day.

We recently stopped for an impromptu picnic lunch at the Natchez Trace State Park, just off I-40 east of Jackson, TN. The ravine below the picnic area is completely overgrown with kudzu. I hated to see that.

The picnic area is shaded by tall pine trees. A thick natural mulch of pine needles and cones pads the ground. Here and there, a long runner of kudzu was snaking across the pine needles, looking for a tree to climb. I am sure the area is regularly patrolled by park workers to hold the kudzu at bay

When we went to the museum at the park headquarters after lunch, we learned that kudzu was planted in Natchez Trace State Park during the 1930's for erosion control. I had a vague recollection that kudzu had been planted for erosion in Florida, but I didn't realize that it had also happened in Tennessee.

The hilly land in the area had become badly eroded due to deforestation and farming. Through the New Deal and other programs, the land was purchased and the impoverished farmers of the area were resettled elsewhere. Then CCC workers were brought in. They planted pines to reforest the cleared areas and kudzu to hold the soil on badly eroded hillsides and gullies.

This story of farmers being bought out and moved is identical to what happened in the Pennyrile State Forest in northern Christian County, KY (about 30 miles from where I live.) The CCC planted pines in Pennyrile also. I would like to know if kudzu was also planted at that time. (Kudzu does grow there.) I know a forester who works there, and I will ask him.

I've blogged about several different invasive species lately. I don't intend for this blog to become a chronicle of invasive species, but the effects of some of them are so terrible that I can't ignore them!

Monday, June 25, 2007

Five Tall, Narrow Trees

Native trees with a tall, narrow shape

Bald cypress
Image courtesy of the U.S. Geological Survey

These tall trees have a narrow spread and will fit into a small space.

I've noted the maximum height and spread that I found mentioned for each tree in various sources. That size might be attained by a mature tree in optimal conditions. Your tree won't get that big for a while, and it may never get quite that big, through there's an outside chance. Cultivars may be available that will have a narrower spread.

Please note that these trees all require an acidic soil. Also, most of them are susceptible to being blown over by high wind if their branches and/or leaves are heavy with a load of rainwater, ice, or snow.

I've linked the scientific names to a tree description at The Gymnosperm Database. The common names are linked to a tree description on the Virginia Tech Dendrology website.

Here's the list:

Related posts:
Narrow trees for small spaces
Ten Tall-Growing Trees
Five Tall, Narrow, Deciduous Trees

Friday, June 22, 2007

Swamp White Oak: Fast-Growing and Moisture-Loving

Quercus bicolor

Swamp white oakLarge swamp white oak in the Clay Plain forest
(a floodplain of the Hubbardton River in Vermont.)
U.S. Fish and Wildlife Service photo

Swamp white oak is a native tree of many of the northeastern States, particularly the northern Ohio River valley and adjacent areas. (For a county by county map of where swamp white oak grows naturally, visit the Quercus bicolor page on the USDA/NRCS Plants Database, and click on the state that interests you.)

I was excited a few years ago when I finally spotted a swamp white oak. A nice specimen grows near a little creek at an I-24 rest-stop, very near the Ohio River in Illinois. It is growing in exactly the sort of place swamp white oak likes and needs. It prefers a damp site and will tolerate flooding.

It's very important for swamp white oak to have an acidic soil. A soil pH of 6.0 to 6.5 is perfect according to Gary Hightshoe's Native Trees, Shrubs, and Vines for Urban and Rural America*. The USDA/NSRC Plant Guide for Swamp White Oak suggests a soil pH of less than 7.2.

If you're thinking of planting this tree, get a soil test of the potential site through your local university extension office. And if you learn that your soil is alkaline, don't plant a swamp white oak.

A swamp white oak grown in alkaline soil will develop a condition called iron chlorosis. It will look ugly, grow poorly, and die much younger than it should. Iron chlorosis can be treated with various chemicals --but why set yourself up for all those problems?

The swamp white oak also requires soil that is in the finer half of the spectrum -- that is, it likes silts, clays, and loams much more than coarsely textured sandy or gravelly soils.

In the right place, Quercus bicolor will grow as much as 2 feet per year. It will have characteristics one expects of an oak:

1. It will be resistant to wind and ice damage.
2. It will be a nice shade tree.
3. It will be a great tree for wildlife, providing food to a wide range of species.

It would be easy to transplant a young swamp white oak if you find one in the wild. Swamp white oak has a spreading, shallow-growing root system.

Dig it up with as much dirt as possible using "ball and burlap" techniques to keep the soil in place. Plant it at the same depth that it was previously growing. The cool weather of spring or fall is the best time. Or collect the acorns in the fall and plant them yourself instead of relying on Mother Nature.
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*Bibliographical info for Native Trees, Shrubs, and Vines for Urban and Rural America by Gary L. Hightshoe is provided at the bottom of this column.

Wednesday, June 20, 2007

Hollow tree, broken in a thunderstorm

Hollow trees should not be filled with concrete.

This huge old maple tree has probably been hollow for many years. Fungi gained access to the heartwood through a wound, and rot set in. Nevertheless, the tree attained an impressive girth and height.

I don't know if the homeowners were aware of the hollow in the tree and its potential to cause damage. They were certainly fortunate that it didn't fall on their house or vehicle. It did fall onto the highway, but luckily no cars were passing at the time.

We didn't have very much wind or rain the day this tree broke, but it was enough to bring the old tree down. I know the homeowners will miss it terribly.

Just for the record, don't ever let anyone talk you into pouring concrete into a hollow tree. When the tree does eventually die and it must be removed, how can you cut up a concrete-filled tree with a chain saw? And besides that, the cement will chafe inside the cavity as the tree moves in the wind. It can accelerate the decay and seriously injure the tree.

Read more -- Tree Cavities: To Fill or Not To Fill

Tuesday, June 19, 2007

Feral pigs damage ecosystems

Releasing pigs into the forest was a terrible idea.

 Feral pigs at Cape Canaveral, FL -- NASA photo

Mast is an old-fashioned word. The term refers to fallen nuts and fruits that are available to wild animals as winter food.

Sometimes we still hear or read about "mast trees". Often the term is used when talking about food sources for wildlife. Personally, I think of mast trees mainly as oaks, hickories, beech, and walnuts.

While browsing through the archives of Scientific American on the Library of Congress website recently, I came across an article about raising pigs on mast.

In 1864 when the article was written, the American chestnut was plentiful, as well as nuts and acorns from the trees I mentioned above. The author, J.T.D. of Springfield, Illinois, also identifies pawpaw, persimmon, haw and the hazelnut as forms of mast.

J.T.D. wrote that hogs who fed on mast produced pork as good as that from corn-fed hogs. He believed that "sweet acorns" were some of the best mast for producing tasty pork. He advised anyone moving to the "West" (west of the Appalachians) to buy land suitable for turning pigs into the forest where they could eat for free.

Sources of U.S. feral pigs

Hogs set loose in the woods by long-ago farmers like J.T.D. are part of the reason there's a feral pig problem in many parts of the United States today. We can't blame the old-time farmers exclusively, though. There are several other sources of today's feral pigs:

1. Early Spanish explorers brought hogs to the New World, some of which went wild.
2. Hogs were released for hunting purposes in several areas of the U.S. about 100 years ago.
3. Some mindless people are releasing pigs into the wild to this day--illegally in most cases -- so they can hunt them.

Feral pigs: Spoilers of nature

Here are just a few reasons why it's undesirable to have feral pigs in the woods.

1. They compete directly with native wildlife for food.
2. They root and wallow in wildlife habitat, wetlands, stands of endangered plants, croplands, and anywhere they go.
3. They eat small animals and the eggs and young of ground-nesting birds.
4. They transmit disease to domestic stock, and even to humans.

Read more here:
Feral Hogs in Michigan
Feral Hogs: Wildlife Enemy Number One (Alabama)
History of Wild Boars
Google search for "feral hogs"

Sunday, June 17, 2007

Parasitic wasps vs. emerald ash borers

Tiny wasps may be released as a biological control for emerald ash borer

U.S. Forest Service research entomologists from Michigan have completed a study of the emerald ash borer in its natural habitat in China. They discovered three tiny parasitic wasps that keep it under control there.

The three are drawn only to ash trees. Some walk all over the bark looking for eggs to lay their own eggs in; others listen for ash borer larvae below the surface and then drill through the bark and lay their eggs in or on them.

What happens next is a tiny version of the "Alien" movies: After the wasps lay their eggs, the eggs hatch by bursting out of the embryonic borers, killing them.

Source: "Experts seek borer relief" by Dan Gibbard, Chicago Tribune, June 17, 2007.

The research team has recommended to the USDA that these wasps be imported as a biological control for the emerald ash borer.

Fears of the Public

The following comments about the parasitic wasps were posted on a radio station's news site by concerned citizens. They are very representative of concerns expressed in all the articles I read about the possible introduction of the parasitic wasps.

Re: Wasps Could Wipe Out Emerald Ash Borer
Posted: 2007/6/15 1:06 Updated: 2007/6/15 4:07
I sure hope there aren't a lot of people who are allergic to bees and stuff in those areas. Or else the hospitals will be full or maybe even the funeral homes.

Re: Wasps Could Wipe Out Emerald Ash Borer
Posted: 2007/6/14 11:07 Updated: 2007/6/14 11:19
so this sounds good, but what else will these wasps eat? what if they discover something they like better than the ash borer and decimate that species? Is this not why we are inundated with the bad ladybugs?

Fears Addressed

The fears expressed about the wasps killing people are unfounded. The wasps are stingless and very small -- about the size of a straight pin's head.

The introduction of these parasitic wasps could cause unforeseen problems. The concern that they may seek alternate hosts is certainly valid.

"Bringing in an exotic species to control an invasive species can create a lot of problems," said Dr. James Dunn, an entomologist who teaches biology at Grand Valley State University.

"There is no guarantee they will kill just the ash borer -- that's the danger," Dunn said. "Maybe the risk is worth taking, I don't know. It is not a slam dunk, though."

Repeated laboratory tests indicate that the wasps aren't interested in native borers, just the emerald ash borer, [USDA research entymologist Leah] Bauer said.

Source: "Wasps may help fight ash borer in Mich.," an AP story published June 11, 2007.

My Opinion

Personally, I would rather take the chance of introducing the wasps than watch every ash tree in North America die. The bacteria introduced from Japan to help control gypsy moths has worked well, and there's every reason to hope that the parasitic wasps will be a successful weapon against the emerald ash borer.

The emerald ash borer was first identified in 2002 in Michigan, and since then, 20 million North American ash trees have died from infestation. As these ash trees have died, entire ecosystems have been affected. It is a staggering problem.

The decision of whether to release the wasps has not yet been made.

Read more:

Battle of the Bugs: Parasitic moths are to be lined up against the ash borer

Ash borer fight adds wasps

Thursday, June 14, 2007

Trees That Produce Root Suckers

Root-suckering trees can be a landscaping problem.

If you don't want to deal with root suckers (clone trees sprouting up from the roots of a "parent" tree,) don't plant the trees listed below. Some of them produce more root suckers than others, but all of them will send up shoots on a regular basis.

Controlling root suckers by mowingIf you plant them, you can control the suckers by keeping the grass mowed around them. If you aren't vigilant, you may soon have a thicket or a pure stand. If you have a small yard, your neighbors will have to deal with the constant sprouting of root suckers from your tree also.

To help minimize root suckering, avoid any injury to the "parent" tree, such as pruning it or shearing off the tops of its roots with the lawn mower.

This is probably an incomplete list.

  1. Alders --Alnus
  2. Poplars --Populus -- cottonwoods, aspens, poplars (look for non-suckering varieties)
  3. Sumacs -- Rhus
  4. Willows -- Salix
  5. Black locust -- Robinia pseudoacacia
  6. Honey Locust -- Gleditsia triacanthos
  7. Sassafras -- Sassafras albidum (Nutt.) Nees
  8. Blackgum -- Nyssa sylvatica Marsh
  9. Beech -- Fagus grandifolia Ehrh.
  10. Southern Crabapple -- Malus angustifolia Michaux
  11. Wild cherries -- Prunus serotina, Prunus virginiana, Prunus avium, Prunus padus
  12. Wild plums -- Prunus americana
  13. Lindens -- Tilia
  14. Persimmon -- Diospyros spp.
  15. Pawpaw -- Asimina triloba (will create a "pawpaw patch")
  16. Devil's walking stick --Aralia spinosa
  17. Common hoptree -- Ptelea trifoliata
  18. Nannyberry -- Viburnum lentago
  19. Blackhaw -- Viburnum prunifolium
  20. Chinese mulberry -- Cudrania tricus pidata
  21. Chinese jujuba -- Zizyphus jujuba
  22. Juneberries -- Amelanchier spp. (serviceberries, etc.)
Particularly avoid these very invasive root-suckering trees:
  1. White Poplar -- Populus alba
  2. Russian Olive -- Elaeagnus angustifolia L.
  3. Autumn Olive -- Elaeagnus umbellata Thunberg
  4. European Black Alder Alnus glutinosa -- produces root suckers and spreads rampantly by seed
  5. English Elm -- Ulmus procera
  6. Mimosa - - Albizia julibrissin -- produces root suckers and spreads rampantly by seed

Tuesday, June 12, 2007

Leaves of blackjack oak (maybe)

Adventures in leaf identification

I have long-term confusion about some small oak trees along our lane. They grow in tangled thickets of underbrush where it's impossible to even guess how many separate trees there are.

Several times, I've tried to look up their leaves in my books. Every time, I think that they look a lot like bear oak. However, bear oak isn't native here, so I always reluctantly decide on blackjack oak.

Here are leaves from two of these trees, growing near each other. The top row of leaves are from the first tree and the bottom row of leaves are from the second tree. Notice the variation just between the two leaves of the second tree (bottom row.)

The two leaves in the bottom row resemble the two types of leaves I find attributed to the blackjack oak in my reference books. The leaf on the left looks like the blackjack oak leaf in my Audubon field guide*. The leaf on the right is similar to the blackjack oak leaf in Trees and Shrubs of Kentucky*. Thus, the tree from which the bottom two leaves came is probably a blackjack oak -- but I'm still not sure about the other tree.

The books I've consulted also mention a yellowish color and some fuzz along the veins on the underside of the leaf, and bristles. None of the leaves in my photo are fuzzy underneath. And, though they are paler on their underside, I wouldn't call them yellowish. Also, I don't see any bristles on them. But perhaps they'll develop fuzz, color, and bristles as the season advances.

Here's a summary of what I've read about blackjack oaks while once again researching their leaf shape. Blackjack oaks are small scrubby trees with crooked, sturdy branches. Their height is usually less than 40 feet, and often much shorter. They grow in thin soil and dry conditions. They don't like shade, so they are usually found at forest edges or on slopes. All of this is a perfect description of the trees I'm calling blackjacks.

Blackjacks are found throughout much of Kentucky, including my county. They are native to every state in the Southeastern U.S. from eastern Kansas to the Atlantic Ocean. It is interesting to note in a map of their distribution that they do not grow in the Mississippi River valley. I suppose the soil is too rich and damp for them.

Like all oaks, blackjacks have great wildlife value. The acorns are eaten by a wide range of animals and birds, and the leaves, twigs, and bark may be nibbled in some seasons as well.

For biographical info on books I've mentioned in this post, please see the bottom of this column.

Saturday, June 9, 2007

Native trees for poorly-drained areas

Native trees that tolerate a high water table and periods of saturated soil

House built on a poorly drained plain
This post is written with my sister and brother-in-law in mind. They've recently moved to their new house, and they will soon be doing landscaping and planting trees.

Their house is located on a very flat acreage in southwest Missouri. The building site is part of a large flat prairie that extends for several miles (or more) in all directions. I don't know the exact soil type, but it is a clay-like soil, rather than a sandy soil. All in all, it would be considered a poorly-drained, slow-to-dry site.

Here are some native trees of Missouri that might do well for them.

Larger trees to plant farther from the house
The following trees are resistant to wind and ice and will tolerate poor drainage:
  • Kentucky coffeetree (Gymnocladus dioicus)
  • American elm (Ulmus americana)
  • Common Hackberry (Celtis occidentalis)
  • Bitternut hickory (Carya cordiformis)
  • Shagbark hickory (Carya ovata)
  • Common honeylocust (Gleditsia triacanthos)
  • American hornbeam (Carpinus caroliniana)
  • Black maple (Acer negundo)
  • Sugar maple (Acer saccharum)
  • Swamp white oak (Quercus bicolor)
  • Bur oak (Quercus macrocarpa)
  • Pin oak (Quercus palustris)
  • Post oak (Quercus stellata)
  • Eastern red cedar (Juniperus virginiana)
  • Black tupelo (Nyssa sylvatica)

Smaller trees to plant closer to the house
The following trees are resistant to wind and ice and will tolerate poor drainage:
  • Pagoda dogwood (Cornus alternifolia)
  • Flowering dogwood (Cornus florida)
  • Downy hawthorn (Crataegus mollis)
  • Glossy hawthorn (Crataegus nitida)
  • Washington hawthorn (Crataegus phaenopyrum)
  • Dotted hawthorn (Crataegus punctata)
  • Common hoptree (Ptelea trifoliata)
  • Blackhaw (Viburnum prunifolium)
  • Rusty blackhaw (Viburnum prunifolium)
  • Eastern wahoo (Euonymus atropurpureus)

Trees that will make a mess
The following trees are resistant to wind and ice and will tolerate poor drainage:
  • Black cherry, wild cherry (Prunus serotina)
  • Prairie crabapple (Malus ioensis)
  • Osage orange, hedgeapple (Maclura pomifera)
  • American Sweetgum (Liquidambar styraciflua)
  • Sycamore, American planetree (Platanus occidentalis)

Trees that will tolerate poor drainage but are often damaged by weather.
  • Northern catalpa (Catalpa speciosa)
  • Tulip tree, tulip poplar (Liriodendron tulipifera)
  • Red maple (Acer rubrum)
  • Silver maple (Acer saccharinum)
  • River birch (Betula nigra)
  • Cottonwood, eastern poplar (Populus deltoides)
  • Red mulberry (Morus rubra)
  • Willows (Salix)

I have eliminated ashes from my list even though they don't mind poorly-drained sites. The emerald ash borer is moving across the U.S., killing ash trees, and it will reach Missouri all too soon.

Remember, there is always the opportunity to create better drainage if you want to plant a tree that needs it (such as redbuds which my sister likes.) One of the easiest ways is simply to bring in a pile of dirt (from a nearby area so the soil is similar.) Let it settle for a while, and then plant the tree on the mound.

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Friday, June 1, 2007

Ten ways to reduce wind damage to (and from) your trees

Help your trees survive strong winds

Trees and wind1. Choose slow-growing trees that are known for wind resistance and strong wood, rather than fast-growing varieties with weak wood.

2. Avoid trees with shallow rooting patterns if you live in an area of frequent high winds.

3. Trees that are planted so they become a small grove as they grow will have more wind resistance than a single specimen. However, do not overcrowd them.

4. Plant small trees close enough to your house to shade the east, west and south walls, and keep taller trees at a distance.

5. Do not add compost or rich soil to the hole where you plant a tree, or the tree's roots may not develop properly.

6. Prune trees to encourage strong growth and good form, starting a couple years after planting. Eliminate:
  • branches that cross or rub
  • branches with weak crotches (less than 45° between branch and trunk)
  • branches that grow toward the center of the tree
  • double leaders (more than one main stem)
  • small branches that clutter the center of the tree

7. Help a young tree grow strong against the wind -- don't stake it tightly, and don't stake it longer than absolutely necessary.

8. Do not injure the trunks, branches, or roots of your trees.

9. Do not give your trees strong nitrogen fertilizer as this often promotes excessive leaf growth. The extra leaf surface can increase wind resistance, collect rain, and make the tree top heavy.

10. Remove mature trees that become hollow, diseased, weakened, one-sided or excessively leaning.

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Enrich your life with the study of trees.

"The power to recognize trees at a glance without examining their leaves or flowers or fruit as they are seen, for example, from the car-window during a railroad journey, can only be acquired by studying them as they grow under all possible conditions over wide areas of territory. Such an attainment may not have much practical value, but once acquired it gives to the possessor a good deal of pleasure which is denied to less fortunate travelers."

Charles Sprague Sargent (1841-1927)

Print references I frequently consult

Benvie, Sam. Encyclopedia of North American Trees. Buffalo, NY: Firefly, 2000.

Brockman, C. Frank. Trees of North America: A Guide to Field Identification. Ed. Herbert S. Zim. New York: Golden, 1986.

Cliburn, Jerry, and Ginny Clomps. A Key to Missouri Trees in Winter: An Identification Guide. Conservation Commission of the State of Missouri, 1980.

Collingwood, G. H., Warren David Brush, and Devereux Butcher. Knowing Your Trees. Washington: American Forestry Association, 1978.

Dirr, Michael. Dirr's Hardy Trees and Shrubs: an Illustrated Encyclopedia. Portland, Or.: Timber, 1997.

Elias, Thomas S. The Complete Trees of North America; Field Guide and Natural History. New York: Book Division, Times Mirror Magazines, 1980.

Grimm, William Carey. The Book of Trees;. Harrisburg, PA: Stackpole, 1962.

Hightshoe, Gary L. Native Trees, Shrubs, and Vines for Urban and Rural America: a Planting Design Manual for Environmental Designers. New York: Van Nostrand Reinhold, 1988.

Little, Elbert L. National Audubon Society Field Guide to North American Trees. New York: Chanticleer, 1996.

Martin, Alexander C., Herbert S. Zim, and Arnold L. Nelson. American Wildlife and Plants. New York: McGraw Hill, 1951.

Mitchell, Alan F., and David More. The Trees of North America. New York, NY: Facts On File Publications, 1987.

Randall, Charles E. Enjoying Our Trees. Washington: American Forestry Association, 1969.

Settergren, Carl D., and R. E. McDermott. Trees of Missouri. Columbia: University Extension, 1995.

Sternberg, Guy, and James W. Wilson. Native Trees for North American Landscapes: from the Atlantic to the Rockies. Portland: Timber, 2004.

Wharton, Mary E., and Roger W. Barbour. Trees and Shrubs of Kentucky. Lexington: University of Kentucky, 1973.

Wyman, Donald. Trees for American Gardens. New York: Macmillan, 1965.

Photos and text copyright © 2006-2010 by Genevieve L. Netz. All rights reserved. Do not republish without written permission. My e-mail address is