The trail area just south of Princeton Landing hosts a large variety of small plants bushes and trees. I don't know all the varieties and haven't done a count but there are many. You could easily spend months studying them, particularly if you got into such details as the history of some of the plants including their earlier uses, transfer from Europe and Asia, naming and associated anecdotes. I'll attempt a brief introduction.
If you browse good field guides for trees and smaller plants you'll find that much of the flora in our area had important uses in pre-colonial and colonial times, as food, medicine, lumber, dyes and cordage. Most of these uses have disappeared under the pressure of industrialization.
Among the trail area plants with interesting histories are the following.
- The winter cress, a yellow flowered member of the mustard family is also known as scurvy grass because it was grown as a winter salad green in colonial times. You won't, of course, find it in the standardized selection of greens available in your supermarket.
- The blue flowered gill-over-the-ground, also known as ground ivy, was used to ferment and flavor beer before hops prevailed. Gill comes from the French guiller, to ferment.
- Willow bark was the original source of acetylsalicylic acid, otherwise known as aspirin, its original trademark name.
- Blackwillow was once the main source of charcoal for gunpowder.
- White oak was an important source of lumber for shipbuilding while the northern red oak was, and is still, a major source of lumber for other purposes.
- Ink and cinnamon red and black dyes were made from the bark of the red oak in colonial times.
- Native Americans made very serviceable twine out of the stem of the Indian hemp plant.
The Ailanthus, known also as the tree of heaven, a native of China, does well in urban environments where other trees don't thrive. You often see it in empty lots in New York City. It will even grow out of cracks in the pavement. This was the tree of " A Tree Grows in Brooklyn." One would imagine from its celestial name that it had a more glamorous role in its place of origin.
Knowledge of some of these plants and many others was important to health and survival in colonial times and knowledge of others was widespread among artisans who used them. This whole area of knowledge is largely lost to most of us. We walk the trail or in other natural environments to enjoy the scenery and the occasional wild-flower that attracts our attention without realizing that we are surrounded by the natural resource base of earlier generations.
The trail area is an unusual environment in that most of it is land fill dredged from Carnegie Lake and put into the basin surrounded by the trail a little less than thirty years ago. As a result of the relative recency of the fill, trees in the area are smaller than those south and west of the dike on which the trail is built. There is also an abundance of cottonwoods (named for their cotton-like seeds, and recognizable by the aspen-like waver of their flat stemmed leaves) and black willows (narrow leaves), particularly on the east side of the area. The willow and cottonwood seeds, which, unlike those of most other trees, can survive immersion, may have come from the dredged soil. There are also fewer of other varieties, such as oak and maple, in the fill area inside the trail than there would normally be, since dredged soil is inhospitable to them due to lack of certain organisms.
There are however a fair number of maples along the trail, of at least four varieties, Norway, red and silver, with the heaviest concentrations on the west side of the trail. The Norway maple is recognizable by its dark green leaves. The sugar maple is distinguished from the Norway by its lighter leaves, and the red maple by its deeply notched leaves as well as a somewhat lighter leaf color. The silver has even more deeply notched and generally narrower leaves the undersides of which take on a silverish white color in late spring and summer.
There is also a scattering of oak, ash, locust, black cherry and sumac trees in the area. The oak are of the black, northern red, pin and white varieties. The black oak has a broad leaf, as oak leaves go, while the pin oak and northern red have narrow leaves which can be distinguished by size. The pin oak leaf is noticeably smaller than the red, 5" in length as opposed to 9". The white oak is easily distinguishable by the rounded lobes of its leaves.
At this point I don't know what varieties of ash trees we have, or even if all of those that look like ash to me are ash rather than hickory, many of which, to my untrained eye, are similar for much of the growing season without seeds (nuts in the case of hickory) to distinguish them. Ash and hickory in general are recognizable by their paired rows of pointed leaves; each leaf, except for that at the point of the leaf stem, is exactly opposite the other, as distinguished from the elm the leaves of which are staggered along a twig. The ash type leaf is technically known as compound pinnate, compound signifying five or more leaves on a stem, and pinnate, arranged in rows, as distinguished from palmate, arranged in clusters.
The locust also has compound pinnate leaves but rounded rather than pointed and generally many more to a stem than ash leaves. The black locust has leaves the shape of and almost the size of a teaspoon, and its bark has exceptionally deep furrows as it ages, which give it a weather-beaten, sinewy look. The honey locust's leaves are more elongated and it has smoother bark.
The sumac tree has an array of leaves similar to the locust but pointed rather than rounded. The black cherry is distinguished, like the domestic cherry, by horizontal stripes in its bark at least in the younger trunks and branches.
The fill area also abounds in phragmites, the tall tufted reeds often found in swampy places in this part of the country. You'll see clusters of stalks which are actually all the same plant, as you'll find if you try to pull one up. This is a characteristic of the grass family, including lawn grass.
Aside from the phragmites two of the dominant kinds of ground cover in the trail area are garlic mustard and Japanese honeysuckle^ (a vine, most often freestanding, not the garden variety bush with which we are more familiar, but with a similar flower). Both of these plants are imports, as is also the multiflora rose, a bush with small white flowers, also found in great abundance in the trail area and all over this part of the country. It was imported from Manchuria as hedgerows and quickly spread. The Japanese honeysuckle was brought to the U.S. for decorative purposes while garlic mustard was probably imported by accident. Like many imports these plants, lacking natural enemies here, and being especially hardy, have out-competed native species in their preferred environments. The most notorious of these invaders, perhaps, is kudzu (also Japanese) but others are more widespread in this part of the country.
Also abundant are:
- Goldenrod, easily identifiable once it blossoms by its dense clusters of small yellow flowers;
- Pokeweed, identifiable by its long, pointed oval leaves, sparse, elongated clusters of small white flowers and, in the late fall, hanging clusters of purple berries;
- White asters with blossoms that resemble daisies and are of the same family, but are generally smaller than daisies and sometimes have fewer petals;
- Boneset with loose clusters of small white flowers;
- Indian grass, which has sparse clusters of very small yellow flowers that hang down in a bell-like fashion; and
- Poison ivy, recognizable by its three-leaf clusters which is found in great quantities next to the trail and on many of the trees-"three leaves, let it be!"
Also to be found in the trail area are:
- Raspberries and blackberries;
- Fox grapes, a vine;
- Mullein, distinguished by its furry leafs and tall rod-like clusters of greenish yellow flowers;
- Jack-in-the pulpit;
- Gill-over-the ground, with its bright blue flowers;
- Various kinds of grasses and sedges.
Grass and sedge are an example of convergent evolution, life forms of different lines of descent evolving to resemble one another. Though often similar in appearance, they belong to different branches of the evolutionary tree.
The ground cover changes over the course of the growing season. For instance the gill-over-the ground becomes less noticeable by early summer when it is no longer in blossom and is overtaken by taller plants. The garlic mustard blossoms disappear not much after and the Japanese honeysuckle is largely overtaken by other plants as the summer wears on. By late summer the pokeweed is large and dominant with a lavish show of berries, and goldenrod has become prevalent in non-swampy open areas. The large spikes of the mature mullein are also conspicuous by late summer. Thus, if you walk the trail at various periods of the growing season and look carefully, you'll find that the plant picture, which may look much the same on superficial observation, has actually changed greatly.
Returning to the non-native plants found in the trail area, another import is the Paulownia (pronounced polonia), also known as the empress or princess tree, named after Anna Paulowna, daughter of Czar Paul I, who married William II of Orange and is great grandmother of the present queen Beatrix of the Netherlands. This tree is of Asian origin, despite the European name, which I imagine was given it by Dutch traders who brought it back from China. Its leaves are almost identical to those of the catalpa, but its flowers, spectacular clusters of trumpet shaped blossoms, are mauve rather than white, and it has striated bark. Its wood is valued for carving by the Japanese.
The Paulownia is an object lesson in the problem of identifying trees. You sometimes can't be sure what you're seeing until you see plants in spring and fall, when you have blossoms and seeds to guide you, as well as in summer. The ailanthus and sumac are another pair that can be confused if you see them in the spring or summer. However, ailanthus seeds, which appear only in the fall, come in large green, hanging clusters, while sumac seeds are in the form of erect clusters of red berries. The underside of silver maple leaf silvers only in late spring or early summer. In early spring the underside looks much like that of other maples. As a final example the ash and the Boxelder are distinguishable by their seeds, which in the case of the Boxelder are winged like the seeds of the maple, while those of the ash are in the form of small blades. As we've seen, trees may also be differentiated by their flowers, as in the case of the Paulownia and the catalpa.
The similarity in appearance of many of the plants just discussed is a good illustration of convergent evolution. All the pairs discussed in the preceding paragraph belong to different families and are unrelated. The Boxelder, for example, is of the maple family, while the kinds of ash we have in the trail area are of the olive family. Sumac is of the cashew family, while the ailanthus is from an unrelated family with a name familiar only to specialists. The Paulownia and catalpa are also from unrelated families with unfamiliar names.
A final interesting plant is the lemon mint of which there is a small patch near the culvert just west of the rows of maples at the north end of the trail. They're low plants, with mint-like leaves, next to a 21A foot long piece of concrete set in the ground just east of the culvert. If you crush the leaves between your fingers and sniff them, you'll find they emit a very pleasant aroma rather like that of key lime pie. However, they don't have much taste.
The above list is by no means exhaustive. It covers merely the most important species found in the trail area, or at least those I happen to have observed. If you want to know more about the flora of the trail area, you can get, at almost any bookstore, field guides for trees and flowering plants found in this part of the country, but you'll find it takes a good deal of head scratching to identify many of the varieties. Observing them in different seasons, so that you can see flowers and seeds as well as the leaves and bark, helps greatly.
By Dick Greene, September 2001