Ten Tree Species

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Ten Tree Species: A Guide to Recognizing Special Natural Areas in the Merrimack Valley of New Hampshire

Ten Tree Species:

A Guide to Recognizing Special Natural Areas in the Merrimack Valley of New Hampshire

Jason Sachs

Preliminary draft Apr 21 2009

work in progress: still under construction

This page may be viewed online at http://www.nhbotany.org/content/ten-tree-species

Overview

The Merrimack Valley contains a number of remarkable habitat types, many of which are at the northern end of their geographic range and do not occur in many other places in New Hampshire. Some examples of these, such as the Concord Pine Barrens, are well-documented and well-known, but others are either undocumented or not well-known to community leaders and planners.

Protecting these special natural areas presents a challenge: the area within roughly 20 miles of the Merrimack River between Concord and Nashua contains New Hampshire's largest population centers and its heaviest transportation corridors (including I-93 and the Everett Turnpike), and is within commuting distance of Boston and its northern suburbs, making unprotected lands at great risk for residential and commercial development. It is vital that we identify areas of high ecological value for our plant and animal species, to protect those areas which are important for our state's biodiversity.

This guide contains descriptions of ten tree species which can be used as indicators of special natural areas in this region of New Hampshire:

  1. Chestnut oak (Quercus prinus)
  2. Shagbark hickory (Carya ovata)
  3. Pignut hickory (Carya glabra)
  4. Basswood (Tilia americana)
  5. Hophornbeam (Ostrya virginiana)
  6. Hornbeam (Carpinus caroliniana)
  7. Sycamore (Platanus occidentalis)
  8. Pitch pine (Pinus rigida)
  9. Black gum (Nyssa sylvatica)
  10. Atlantic white cedar (Chamaecyparis thyoides)

All of these are easily recognized, and many are well-correlated with some of the rarer forest, floodplain and swampland habitats in this region of New Hampshire. Trees are useful indicators because they may be examined year-round (unlike grasses and herbs buried under snow) and are often visible and recognizable from a distance. Each of these species is described in two ways:

  • photographs and identification hints
  • a description of the natural communities in which they are found

In addition to these ten species, other trees found in this region are mentioned, including five of the most common species (red maple, red oak, white pine, hemlock, and beech) which are indicators of "mainstream" forests in Southern New Hampshire.

All descriptions are non-technical (no dichotomous keys or Latin terms like "terete" or "strigose") and are aimed at anyone interested in studying and preserving New Hampshire's natural landscape.

Natural Communities for the Beginner

The term "natural communities" is used in ecology to refer to groups of plants that are often found together because of their adaptations to various sorts of environmental conditions, including:

  • soil type (rich or poor, acidic or neutral or alkaline)
  • hydrology (dry or wet or seasonally flooded)
  • exposure to sun or wind
  • temperature influences (from altitude, proximity to water, or cold air drainage)

As a rough analogy, natural communities are the ecological equivalent of music types. (Apologies to the professional musicologists here.) Classical, jazz, folk, country, blues, rock, and rap each have different groups of instruments that are commonly used. Some instruments can be viewed as "specialists": if a piece of music uses a bassoon, it is probably classical rather than rap, and music that uses a mandolin is probably folk rather than jazz. Some instruments, such as drums, appear in many different musical styles and are "generalists".

In the same way, some plants appear in many different natural communities, whereas others are specifically adapted to one particular set of environmental conditions.

The natural communities discussed in this guide are taken from the book "Natural Communities of New Hampshire" by Sperduto and Nichols. Southern New Hampshire contains a number of natural communities that are rare (rated S1 to S2S3 in the Natural Communities book), and that fall into one or more of the following categories:

  • Upland forests with nutrient-rich bedrock content
  • South-facing hillsides
  • Areas of sand deposits (Pine barrens, sandy ponds, etc.)
  • Floodplain forests
  • Swamps containing black gum or Atlantic white cedar

Not included here are other rare wetland types — various marshes, river-edge habitats, etc. — that do not contain trees and are generally more difficult to categorize. Excluding these wetlands, if you visit the rare natural communities that fall into the above categories, you can recognize them fairly easily by several characteristic tree species that grow there. In addition, you are less likely to see other tree species that are found in more common natural communities in Southern New Hampshire.

Three of the above types of sites (rich soils, south-facing slopes, and floodplains) support forests that are more hospitable to plant species found further south. Nutrient-rich bedrock and floodplains provide greater concentrations of minerals to plants. South-facing slopes collect more sunlight, and are therefore both warmer and have longer growing season — snow melts earlier — than other areas in this region. (The term "south-facing" should be taken broadly; a "south-facing" slope may actually be closer to west or east-facing; the point is that it faces towards the sun during a good portion of the day.) These two factors are "kinder" to southern plant species, and allow them to overcome the handicaps of New Hampshire's colder climate. As you travel further north in New Hampshire, these southern species disappear primarily due to decreasing temperature and growing season. Tree species in this type of habitat include various oaks and trees like sugar maple and basswood that like "sweet" soils.

Sand deposits are influenced by the history of New Hampshire's glaciers. As the glaciers receded and melted, they washed large quantities of sand towards their southern extent, and are more commonly found in areas to our south such as Cape Cod, Long Island, and New Jersey. Soils with high sand content are often poor in nutrients, acidic, and well-drained. In New Hampshire they are found primarily in the Merrimack Valley and in the Ossipee Lake region. Pitch pine is a characteristic species.

Black gum and Atlantic white cedar are found in shallow acidic basins; they are common along the eastern seaboard south of New Hampshire, and they reach their northern limit here or in the very southern portions of Maine.

Ten characteristic tree species

One last note before getting into detail about these species: it is important to realize the difference between finding one individual tree, and finding many of these trees together. If you find a single one of these trees, it is worth noting the location, as it may be an errant descendant of a nearby population. But a single tree does not indicate a natural community. On the other hand, if you find large numbers of one of these tree species, or moderate numbers of them with large individual trees making up a significant portion of the tree canopy, it is likely that they indicate one of the natural communities that are infrequent in the Merrimack Valley and the area may be worth protecting.

Chestnut oak (Quercus prinus)

There are a number of oak species in New Hampshire, but the one that is most easily recognizable at a distance is chestnut oak. It has bark in thick furrowed ridges, and leaves that are generally oval in shape, with a smooth wavy or scalloped edge. (This puts chestnut oak in the white oak category, with smooth-edged leaves; the red oak category has small sharp points around the margins of its leaves.)

Chestnut oaks are usually found on rocky ridges or south-facing rocky hillsides, where they can tolerate poor soils. A good example of this may be seen at Rock Rimmon on Manchester's West Side, where chestnut oaks are abundant between the bare cliffs of Rock Rimmon and a pitch pine forest. In states to the south of New Hampshire, they are often found in pine barrens or other sandy soils (chestnut oak can be found occasionally in places near Lake Massabesic in the vicinity of the Massabesic Audubon Center).

Shagbark hickory (Carya ovata)

The hickories like rich soil and lots of sun. They have compound leaves: these consist of a number of leaflets along a stalk which all emerge from the same bud in the spring, and serve to present a large surface area for photosynthesis, while at the same time being more resistant to damage by wind than a large simple leaf of the same area. Hickory leaves, in particular, consist of an odd number of oval leaflets, usually 5-11 (although sometimes as many as 17), arranged in pairs along the leaf stalk with a single leaflet at the end.

The husks of hickory nuts split into 4 quadrants as the nut matures.

Shagbark hickory has easily recognizable bark: it splits along vertical lines and forms shaggy strips that bend away from the tree (hence the name). Shagbark hickory nuts are one or two inches in diameter, and are edible (although the squirrels are more likely to get them before we can).

Hickory species in this area are usually found on south-facing rocky hillsides with enough nutrient content that they can outcompete other species, and are not usually found north of Manchester, although there is a population along the floodplain of the Merrimack River in Concord.

Pignut hickory (Carya glabra)

Pignut hickory has bark that does not separate like shagbark hickory does; instead it forms a lattice of diagonal rough grooves that remind me of a lattice-topped apple pie. The nuts are small, about 1/2-3/4" in diameter, and are allegedly edible although there is so little to eat inside that it seems hardly worth the effort to crack them open — for a person at least; they're a good food source for smaller animals.

It is found in the same general habitats as shagbark hickory.

There are other hickory species found in similar habitats; two others in New Hampshire are mockernut hickory (Carya tomentosa) and bitternut hickory (Carya cordiformis), but other than the bright yellow buds of bitternut hickory, they all look fairly similar.

Basswood (Tilia americana)

Basswood has heart-shaped leaves and an odd-shaped fruit: a cluster of small round greenish-brown seedpods on a stalk that emerges from the middle of an oval, somewhat tongue-shaped leafy thing (called a "bract"). The leaves are asymmetric and have serrated edges.

The trunk of a basswood is round with a distinctive set of narrow vertical grooves of irregular lengths that make the flat strips of bark between the grooves look somewhat like a chaotic series of highway lanes merging and diverging. The wood is lightweight and is said to make a hollow thumping if you slap the trunk (although every time I try I just end up hurting my hand).

Basswood is common in floodplain forests, where occasional river floods dump nutrient-rich silt and sand along the banks. It can occasionally be found elsewhere as scattered individuals in forests with rich soils.

Hophornbeam (Ostrya virginiana)

In some areas of the country this tree is known as "ironwood" because it is very hard wood sometimes used for handles of tools. The bark is very distinctive, with a thin, shredded look to it.

Hophornbeam is a good indicator of soil enrichment: look for other trees nearby such as sugar maple, basswood, white ash, or hickory. It's not usually very large, up to 5 or 6" diameter in most cases, and is more of an understory tree. By itself it's not really a good indicator of rare natural communities in this part of New Hampshire, but it's easy to spot and may catch your eye.

Hornbeam (Carpinus caroliniana)

Hornbeam is also known as musclewood: it's a small tree with a ripply smooth gray bark that looks like the tree is trying to flex its muscles or something. It likes to grow near streams or in floodplain forests with enriched soils.

Sycamore (Platanus occidentalis)

Sycamore is a tree with camouflage patching: as it ages its bark flakes off in patches to reveal a layer of a different color underneath. It likes sandy or gravelly floodplains, and is not often found far away from running water unless it has been planted. There is an excellent example (still standing at this writing) outside of the church in Concord just north of where Main Street heads off to the northwest and Rt. 393 begins heading east. These trees can be huge! They are essentially the largest tree east of the Mississippi River. Fruits are gumball-shaped, and the leaves are somewhat similar to maples, with more shallow lobing.

Pitch pine (Pinus rigida)

There are four pine species native to New Hampshire: the common white pine (discussed below), red pine, jack pine, and pitch pine. A fifth, introduced pine that was a popularly planted tree in the mid-1900's is Scotch pine, which has orangish bark towards the upper sections of the tree. Jack pine is found in ledgy areas, in our area only on Mts. Welch and Dickey in Waterville Valley and near Lake Umbagog, with a possible appearance in Crawford Notch. The other pines can be easily distinguished by their needles, their bark, their cones, and their general shape. Pitch pine usually has a crooked, gnarly look to it, and is usually found in dry sandy or rocky upland areas. The needles are in bundles of threes, usually shorter than white pine's bundles of five, and the cones tend to be short and squat. The big giveaway with pitch pine is that it often has needles growing out of the bark along the trunk, making it look like the unshaven, shaggy cousin of our other pines.

Black gum (Nyssa sylvatica)

This tree likes to get its feet wet, preferring to grow in the margins of shallow swamps, primarily in Hillsborough and Rockingham counties. The bark is very distinctive, with grooves on younger trees that with age change into thick, blocky furrows. The trunks tend to be somewhat wavy on younger trees (like it has had a bit too much to drink and can't quite seem to grow straight). The big giveaway for me is to look at the branching angle: nearly every twig or branch comes off of its larger neighbor at almost a right angle. If you stand under a black gum and look up, it appears somewhat like a broken umbrella with spokes coming right out of the trunk. The twigs alternate off of the branches; the leaves are a nondescript oval that often grow in groups forming whorls around the twig. Occasionally in mid-summer you may see the blue fruits, which look like small single grapes. In the early fall this is one of the first trees to start turning color, and it may turn a bright red-orange long before anything else except the red maples.

These have a slow growing habit, and because their wood is not particularly desirable and they tend to be in swamps, they have often been left untouched by timber operations in the state and can indicate habitat that may have been undisturbed for centuries. These are the oldest trees east of the Appalachians, with some specimens in Rockingham County having been verified through core samples at over 700 years of age. Trees of 18" diameter or more can easily be 250 years old.

Atlantic white cedar (Chamaecyparis thyoides)

Atlantic white cedar is one of three "cedar" species in our state, each of which have a distinctive shaggy bark. Northern white cedar (Thuja canadensis) or arbor vitae is found in the northern portion of New Hampshire and likes calcareous fens or mesic forests. Eastern red cedar (Juniperus virginiana) is a juniper, with prickly needles and blue waxy fruits, found in rocky uplands or fields or coastal areas. I have rarely seen it outside of Rockingham County. Atlantic white cedar is a resident of acidic swamps in southern New Hampshire. There are only 500 acres of Chamaecyparis swamps estimated in the state, making it a very uncommon tree. You may find it along with black gum or mountain laurel.

Five common tree species: the usual suspects

The best way I have discovered to find unusual plant species, is to know the common ones, and get used to them, so that when you see something different, it stands out and catches your attention. Natural communities that the following species dominate (i.e. a large percentage of the canopy trees are of one or more of these species) are almost all fairly common in southern New Hampshire. Put another way, these tree species are "generalists", meaning they can thrive under many different environmental conditions. You've probably seen these trees many times.

I should also mention blueberry (Vaccinium angustifolium and other species of this genus): although they are not trees, blueberry species are very common shrubs in the forest understory of New Hampshire. Their presence indicates acidic soils. If you are in a forest and the blueberries suddenly disappear, especially on a hillside, it often means that the soil is rich enough for other low-growing plants to thrive, and it's a good clue to look for other interesting plants.

Red maple (Acer rubrum)

Red maple is also known as swamp maple; if you are in a swamp (as distinguished from a marsh by the presence of trees and shrubs) in Southern New Hampshire, chances are that there are red maples present. They can tolerate a modest amount of flooding at their roots. But they are also found in many upland habitats.

Maples are one of a small minority of tree species that have opposite branching. If you look at the photographs above (or better yet, go out and find a maple tree!) you will notice that the buds and twigs always come off in pairs on opposite sides of a branch. Most tree species are alternate (birches are a very good example), meaning that they form a sort of zig-zag pattern where as you follow the length of the branch, a single twig or leaf grows on one side, then a little further down another one grows on the other side. The only large trees that are native to New Hampshire that have opposite branching are maples and ashes; among the smaller trees and shrubs, ones with opposite branching include dogwoods and honeysuckles.

The seeds of maples are contained in twin flat wing-shaped fruits called samaras or keys, and are sometimes known as "whirligigs" by the way they spin as they fall through the air to the ground. All of the maple trees in our area, except for box elder (Acer negundo), have simple lobed leaves that look vaguely like the leaf on the Canadian flag. (Box elder has compound leaves.) Red maples are one of only two large maple tree species in New Hampshire that have sawtooth edges, and if you count the lobes you will usually see 5 of them (3 major ones and 2 small lobes at the base of the leaf). Silver maple (Acer saccharinum) is a large tree found in floodplain forests with sawtooth edges but fairly deep gaps ("sinuses") between its 5 lobes. Striped maple (Acer pensylvanicum) and mountain maple (Acer spicatum) also have sawtooth edges but are usually 3-lobed, and they rarely get to be more than 20 feet tall or a few inches in diameter.

The new shoots and roundish buds of red maples are often a deep red in color, hence the name. They can be easily distinguished from sugar maples, which have smooth-lobed leaves, brown shoots and pointed conical brown buds.

If you are stuck with trying to identify a tall red maple in winter, your best bet is to try to look at the canopy to see evidence of opposite branching (ashes have opposite branching also, but they have fat, upward-curving twigs and X-grooved bark) or to look at the bark and just get used to it. The bark of red maples is fairly variable but tends to go from smooth gray bark on young trees of only a few inches in diameter, to shaggy brown-gray bark on large, older trees. The grooves of the bark of medium to large red maples are almost exclusively long vertical grooves, sometimes with a slight twist, with one exception: occasionally you may see a sort of "bulls-eye" pattern of circular ringed grooves in some trees, which probably occur where a branch used to be. Many red maples as they get older have fluted trunks near the ground: if you were to look at a cross-section of trunk, it would not quite be round, but sort of "wavy" with a small number (perhaps 4-8) of curved bulges where the trunk flares outwards.

Red maples are among the earliest trees to turn color in the fall, reaching a bright orange-red in September or early October, with some stressed trees even beginning to change color in late August.

Red oak (Quercus rubra)

Of the oak species in New Hampshire, red oak is the only one that is common in the northern part of the state, and is probably the most common oak throughout the state; red oak and white oak (Quercus alba) are the two most common species, with several other oak species only in the southern part of the state.

Red oak has deeply-lobed leaves with pointed tips. Its bark forms long vertical strips or grooves, not as deeply furrowed as chestnut oak. Black oak has very similar leaves, but the bark forms strips that are much shorter, giving the bark a much more "blocky" look. Scarlet oak is similar to red and black oak, but I've never been able to look at an oak tree and think "Aha, that's a scarlet oak!" without a lot of doubt: some professional botanists have told me the best way is to look carefully at the buds and acorns. Oh, and by the way, these species can hybridize with each other, making identification difficult.

Red oak trees that are round and straight and free of knots or lower branches can have high timber value for their use in veneer production.

White pine (Pinus strobus)

White pine has needles in bundles of 5's. It has a dark gray bark that tends to fissure into rough plates that don't separate from each other quite as happens in the smooth-barked red pine (Pinus resinosa, which is uncommon in southern New Hampshire, being more common in the Saco River valley of Carroll County and Oxford County in Maine) or in pitch pine.

This is one of the most common tree species in southern New Hampshire, and in colonial days was so valuable as ships' masts, that the largest trees, marked with an arrow, were reserved for exclusive use of the British Royal Navy, and transported across straight roads to the seacoast; many of these still bear the name of Mast Road today in towns such as Durham, Dover, Epping, and Goffstown.

Hemlock (Tsuga canadensis)

Hemlock is a tree that is very common in shaded areas on the north side of hills in southern New Hampshire. It is shade-tolerant and can grow on rocky, acid soils. Not many trees will grow under the canopy of a forest dominated by hemlocks.

The needles of hemlock are short (about 1cm long) and flat. It has roundish cones that are small, not much more than 1cm in diameter. The other conifers with short flat needles in New Hampshire are balsam fir (Abies balsamea), which has larger cones that point upwards, and is rarely found south of Concord, and yew (Taxus canadensis) which has red "berries" and is more often found in shrub form, rarely more than a foot or two high because it is a favorite food of moose and deer. If you look closely at the undersides of the needles of these three species, you will see two light-colored lines that are whitish in hemlock and fir, and yellowish in yew. These contain stomata, which are tiny pores that let the trees exchange oxygen and carbon dioxide.

The hemlock is under threat from an invasive insect called the hemlock woolly adelgid which is native to Asia and has spread northward from Virginia over the past few decades. It has been found in several towns in the Merrimack Valley in recent years, so please keep a lookout for this pest; if you see a whitish woolly coating on the underside of hemlock twigs in New Hampshire, please contact the N.H. Forest Health Program at 271-7858.

Beech (Fagus grandifolia)

This is a tree with so many distinctive features.

We had a beech tree in our back yard when I was growing up. I didn't know what it was then, and I haven't been back there since we moved away in 1983, but I know it was a beech from the memory of finding lots of odd, triangular nuts in roundish cases with small flexible spines like the hooks of a piece of velcro. Beech nuts are a favorite food of bears; sometimes you can find beech trees with clawmarks visible on their otherwise-smooth gray bark.

The buds on beech trees are long (2 or 3 centimeters) and very pointy. Don't run around in a beech forest in the winter and early spring, unless you are wearing eyeglasses. The leaves are generally oval with small shallow teeth, and are marcescent, meaning they often stay on the tree throughout the fall and winter, dropping only in the spring. It is quite a sight to stand among beech trees in winter when the wind shakes the leaves.

Beech trees are often found in colonies (they sprout from root suckers) and are very good at regenerating: if you cut them down but leave the roots, they can resprout. They are shade tolerant, often found with hemlocks.

Notes and other miscellanea

Acknowledgements

Thanks to Deb Lievens and Joann Hoy for reviewing a draft of this page and for suggesting additions and changes.

Work-in-progress

In case you are reading this page in print: this page may be found online at http://www.nhbotany.org/content/ten-tree-species where you can follow some useful hyperlinks and view larger copies of the photographs.

In going through my photograph collection for this page, I realized I am missing a number of important pictures (leaves and nuts of pignut hickory, basswood leaves, hophornbeam leaves, sycamore fruits, red oak leaves, white pine needles, hemlock bark, and cones from pitch pine, white pine, and hemlock), which are now on my list for things-to-photograph for 2009. So stay tuned!

What to do if you find one of the 10 indicator species

Treat it as a lead to something interesting. If you know someone who's very familiar with trees, ask them to double-check your identification. Talk to your town's Conservation Commission and let them know you found an interesting site. (If you found them on private property, please be sure to speak with the landowner first, to let them know what you've found and to make sure it's okay to discuss with others; some landowners may not appreciate other people getting involved in what's on their property, especially if those people are connected with town government.) Some of these sites, especially those on public land, are already well-known to groups such as the Nature Conservancy or New Hampshire Natural Heritage Bureau, but with a land area of 6 million acres, and a handful of people to study this state's botanical resources, there are surely many significant sites in New Hampshire that are yet to be discovered.

There are some of us in the New Hampshire Botanical Club who would be glad to take a look at interesting botanical areas. We will add an email address to this publication as soon as one is set up.

For further information

Online information

Books

  • Trees and Shrubs (Peterson Field Guides), George A. Petrides. Houghton Mifflin, 1973. ISBN 039535370X. Illustrations, no photographs. My favorite for general use as a field guide.
  • The Tree Identification Book, George W. D. Symonds. HarperCollins, 1973. ISBN 0688050395. Detailed black and white photographs of leaves, bark, seeds, etc.
  • Trees of North America (Golden Field Guides) Frank Brockman, et al. Macmillan, 2001. ISBN 1582380929. The name of Herbert S. Zim is enshrined forever in 1950's and 1960's-era field guides for children and young adults, with its exclusive use of the distinctive sans-serif typeface Futura (look for the curveless vertical-stroke j). It's not particularly detailed but describes and illustrates a huge number of tree species throughout North America, including a number of obscure species in tropical Florida. Species are organized taxonomically by family and genus, and include range maps.
  • A Natural History of Trees of Eastern and Central North America, Donald Culross Peattie. Houghton Mifflin Harcourt, 1991. ISBN 0395581745. If you want to learn to identify trees, the previous guides are good. This is not a field guide but rather a rich, descriptive book full of expository anecdotes, historical information, and other apocrypha.