Red oaks

It's not a matter of black and white! The two young oaks pictured above are a white oak and a black oak growing in the woods in Edgartown Massachusetts. To label them black and white seems like quite an exaggeration, but the trees are so called because of their bark color. (The lightest flecks on both trees are lichens, not bark.)

The complex oak genus has hundreds of species. Many of the species complicate life for classifiers by cross-breeding with each other. Botanists divide the oaks into two groups: the white oak group and the red/black oak group.

The majestic northern red oak, one of the two headliners of the red/black oak group, is New Jersey's state tree. Plainfield is blessed to have many beautiful examples. Red oaks are the fastest growing of the native oaks. We shouldn't be surprised that red oaks are some of the largest trees in Plainfield.

There is a very fine red oak at 916 West Eighth Street, pictured above. How to recognize it as a red oak, Quercus rubra? First, you can put it in the red/black oak group by observing that the lobes of the leaves end in points, (bristle tips). The leaf lobes of the white oak group, by contrast, are rounded. The photograph below shows a red oak leaf on the left and a white oak leaf on the right. The bark color also helps in assigning a group.(1)

That's a start, but how do we know that it's a red oak, and not another member of the red/black group? How do we distinguish it from a pin, scarlet, or black oak? Like red oaks, all those other three species have lobed leaves with bristle tips, and all can be found in the Plainfield area. Red oak leaves are easily distinguished from pin (Quercus palustris) or scarlet (Quercus coccinea) oak leaves because the red oak leaves are much larger. Their lobes are also much less deeply cut. The large acorn and the leaf on the right in the photograph below are from a red oak. The leaf on the left is from a pin oak.

Black oaks (Quercus velutina) can be more difficult to distinguish from red oaks. Black oaks have large leaves, but the leaves are more leathery and lustrous than red oak leaves. Unfortunately, they interbreed quite readily with red oaks, so it's hard to know sometimes whether or not you're really looking at a black oak. (2) Other features of the trees can help with speciation. Red oaks have much larger acorns than black oaks. Red oak acorns have a distinctive look, with a very shallow, saucer-like cap. Mature red oak bark is described as resembling interweaving ski tracks.

Another very handsome, mature red oak is at Stelle Avenue near Central. This magnificent street tree was the subject of some concern two or three years ago when the owner of the adjacent Coriell mansion proposed to restore the semicircular driveway that had once opened onto Stelle Avenue. The driveway was to encircle the red oak. Because the house was being converted to a B & B, the fire department wanted the driveway to be wide enough to accommodate fire trucks. The Historic Preservation Commission intervened to have the driveway narrowed so as to limit damage to the tree's roots.

The handsome red oak at the corner of 1300 Prospect Avenue at the corner of Hillside has a vase-like shape reminiscent of that of an American elm.

The massive red oak at 947 Fernwood pictured below was given special recognition as a specimen tree by Mayor Robinson-Briggs at this past April's Arbor Day celebration.

Another very fine red oak is at 912 Central Avenue. I measured its circumference today at 17 feet at breast height.

(1) Bark color is not necessarily a reliable indicator. Chestnut oak (Quercus prinus or Quercus montana), a member of the white oak group, has bark that is quite dark gray, an exception to the general rule that trees of the white oak group have light-colored bark. The chestnut oak pictured below is on Park Avenue near Randolph Road, across the street from Muhlenberg Hospital. See the January 13, 2008 posting of Plainfield Trees for additional differences between oaks of the white and red/black groups.

(2) The Trees of Pennsylvania and the Northeast, Charles Fergus, Stackpole Books 2002, p. 113.

Copyright Gregory Palermo

From Tree Hugger to Bug Hugger

Is your sleep disturbed by worries about disappearing spotted owls and snail darters? Maybe the objects of your concern are too grand. What you should really be worrying about is bugs: native bugs and the native plants that sustain them. That is the argument advanced by professor of entomology Douglas Tallamy in his recent book, Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens.(1) He says that we are starving our insects by replacing the native plants that they eat with exotic plants that they can't even recognize as food.

Native sweetbay magnolia. Native insect? Click to enlarge.

Starving the bugs sounds like a great idea, right? Maybe not. Tallamy presents insects as unloved heroes that transform the stored energy in plants into food (themselves) for the next level up in the food chain. In order to transform themselves into bird food, for example, insects must have food of their own to eat. But we are depriving them of food by replacing the native landscape with foreign plants. The vast majority of our insects are dietary specialists; the only foods they are capable of eating are members of the native plant community with which they have co-evolved over millions of years. Those are the foods to which their anatomy and physiology are adapted. They have as much success eating foreign plants as we would have if we tried to adopt the koala bear's diet of eucalyptus leaves. Without native plants, the insects have nothing they can eat, and they perish. With the insects gone, all of the food chain above insects will collapse.

American elm 1267 Park Avenue

The differences between the numbers of insects that can eat native versus foreign plants can be startling. Native oaks can provide food for over 500 different native insect species. Eucalyptus, an exotic, is eaten by only one native insect species. Native plants in Pennsylvania were found to support 35 times more caterpillar biomass, the preferred source of protein for most bird nestlings, than alien plants supported.

Native northern red oak, New Jersey state tree, West 8th St

How big a problem can this insect starvation be? Biodiversity depends on space. The more space, the larger the number of species that can be supported. The relationship is linear.(2) Only 3-5% of the lower 48 states remains undisturbed habitat for plants and animals. The rest has been paved, farmed, taken over by noxious foreign weeds like kudzu and Japanese honeysuckle, or transformed into suburban gardens dominated by exotic shrubs and vast lawns of non-native grasses. Tallamy points out that suburban lawns cover about 62,000 square miles of this country, an area more than eight times the size of New Jersey that is devoted to alien grasses.(3) Worse, 43,000 square miles of blacktop has been spread over the landscape, equal to five and a half New Jerseys. If we have eliminated much of the native vegetation from 95-97% of the American landscape, we can expect to lose 95-97% per cent of our native flora and fauna over time, as extinction adjusts the number of species to the land area that remains. Tallamy cites the toll of habitat destruction on Delaware, where he teaches. As of 2002, Delaware had lost 78% of its freshwater mussel species, 34% of its dragonflies, 20% of its fish species, and 31% of its reptiles and amphibians. Forty per cent of all native plant species in Delaware are threatened or already lost.

American holly East 9th Street

At this dismal point in his book Tallamy offers a ray of hope: suburban gardeners to the rescue! If suburbanites, who control a large swath of the landscape, were to plant native plants on their properties, the countryside could still support a diverse flora and fauna. Mix some American elms in with all those Zelkovas. Make your lawn smaller, and plant a meadow. Tear out some of your English ivy and Japanese pachysandra and plant mayapples. I repent ever having written that foreign, kousa dogwoods have the advantage of not being attacked by the borers that plague native flowering dogwoods (a good example of just what Tallamy is talking about). How petty of me ever to have planted exotic hollies instead of American hollies because of the Americans' problems with leaf miners! I'm going to be beating myself up for years over this. But as part of my rehabilitation program, I will spread the word about Tallamy's book, essential reading for anyone who plants.

Native black walnut leaf nibbled by, no doubt, native insects

(1) Tallamy, DW. Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens. Timber Press, 2007.

(2) Tallamy cites the work of Michael Rosenzweig at the University of Arizona to support his claim that species diversity decreases in proportion to the loss of available space. His very cursory discussion of this important underpinning for his argument is, for me, the weakest part of his book. I would like to have seen Rosenzweig's data and analysis described in detail.

(3) If you would object that Kentucky bluegrass is a native, you would be mistaken. Its seeds were imported by European settlers in the digestive tracts and droppings of cattle.

Copyright Gregory Palermo