Of course you will want to know what you're walking on. Dogtown is underlain by dense intrusive granite of Paleozoic origin (570 to 245 million years before present, BP). It's very dense because it was once subjected to pressure by an overlain layer of sedimentary rock, which was worn away by the Laurentide glacier by about 15,000 years BP. The Laurentide ice sheet was formed in Canada about 75,000 years BP and most recently advanced into New England during the Wisconsin stage cooling around 25,000 years BP. As the glacier retreated north due to global warming beginning about 18,000 years ago, it left behind a lot of rocky debris (some carried down from as far as Newfoundland) which on Cape Ann formed what geologists call a terminal moraine. This glacial till on the Dogtown site contains particularly large rocks and some very large surface boulders called erratics. For a complete review of this history see Margaret Martin's good paper Laurentide Glaciation of the Massachusetts Coast (Quaternary Geology, Fall 2008).
Dogtown soils are derived from mixed, loose sandy glacial till with lots of big rocks in it. They are shallow, acid and excessively drained on uplands, where they have low water holding capacity. Sandy loams in the Annisquam series (soil taxonomy lingo) are common, poorly suited for productive agriculture and woodland due to droughtiness and low fertility. Human occupation of Dogtown has undoubtedly further reduced the quality of upland soils. The numerous swamps in Dogtown Common occur in areas where poor drainage is the limiting factor. Soils may be saturated with water from late fall through early summer. While their parent material is of glacial origin, drainage conditions have led to soils with higher organic content (i.e. dark, mucky and yucky) than those of adjacent upland. In hollows and along streams, better soil moisture conditions (adequate moisture and good soil aeration) have resulted in good forest growth and greater species diversity. See Soil Survey of Essex Co. MA, Southern Part for more than you will want to know about Cape Ann soils.
Dogtown Common forests have characteristics typical of the Northeastern Coastal Forest in the Seaboard Lowland Physiographic Province. Its upland eastern and central portions mainly support a Black Oak (Quercus velutina)-Scarlet Oak(Q.coccinea) Community (S3S4). [See Swain, P.C. and J.B. Kearsley. 2001. Classification of the Natural Communities of Massachusetts, Natural Heritage and Endangered Species Program, Massachusett Division of Fisheries and Wildlife. The publication is available on line.] This community in Dogtown Common also contains secondary tree species such as red maple (Acer rubrum), gray birch (Betula populifolia), white or paper birch (Betula papyrifera), red cedar (Juniperus virginiana), black cherry (Prunus serotina), black gum (Nyssa sylvatica), and sassafras (Sassafras albidum).* There are occasional pitch pine (Pinus rigida) and white pine (Pinus strobus). One mostly notices blueberry (Vaccinium sp.) and greenbrier (Smilax rotundifolia) in the shrub layer. Bracken fern (Pteridium aquilinum) is common. There are grassy open areas. This forest is the sort found on land recovering from fire and human disturbances on poorer soils. Trees are relatively small and young (
<100 years). Many of the black oak trees appear to be coppice (formed from sprouts after fire or cutting).
*Note: Scientific names will be given at first mention of the species; thereafter, common names only usually. The authority for scientific names is Manual of Vascular Plants of Northeastern United States and Adjacent Canada 2nd ed. by H. A. Gleason and A. Cronquist, New York Botanical Garden, Bronx, NY. 1991. The Illustrated Companion to this Manual authored by N.H. Holmgren and published by the N.Y. Botanical Garden in 1998 is a very useful but heavyweight supplement. You may also find helpful The Vascular Plants of Massachusetts: A County Checklist by Bruce A. Sorrie and Paul Somers and published by the Massachusetts Natural Heritage and Endangered Species Program in 1999.
Black oak is in the red oak group along with closely related scarlet oak. They may grow together in places like Dogtown and be mistaken for each other. They are notorious for having illicit interspecies sex when on the same site, and produce weird hybrids. My observations so far in Dogtown suggest that black oak is predominant, if not wholly in charge. Good black oaks have orange inner bark as a distinctive characteristic; check this out gently with a pen knife, not a chainsaw.
Forest on the eastern portion of the area is slightly richer in species and growth, though still predominantly a black oak community. For example, beech (Fagus grandifolia) is more abundant (especially young trees), and one occasionally sees white pine, sugar maple (Acer saccharum), sweet birch (Betula lenta) and yellow birch (Betula alleghaniensis). A few hemlock (Tsuga canadensis) persist, though the exotic and invasive woolly adelgid (Adelges tsugae), a sap-sucking insect, has killed much of the area's hemlock population. Cinnamon fern (Osmunda cinnamomea), lady fern (Athyrium filix-femina), sweet pepperbush (Clethra alnifolia) and spicebush (Lindera benzoin) are characteristic of the moister areas in hollows and lower parts of slopes. And it is good to see Canada mayflower (Maianthemum canadense) and wild sarsaparilla (Aralia nudicaulis) becoming common throughout.
Dogtown Common includes some classic red maple swamp communities: The Massachusetts Natural Heritage and Endangered Species Program's Red Maple Swamp (S5). In Dogtown swamps, red maple is the principal tree species; American elm (Ulmus americana) and white ash (Fraxinus americana) occur occasionally. The understory is rich with shrubs and vines, including some really nice poison ivy (Toxicodendron radicans) on trees. There is luxurious cinnamon fern and some 300 other species of nonwoody plants, according to the New Hampshire Department of Environmental Service's Environmental Fact Sheet on the community. I haven't checked them all out. Swamp edges are particularly rich with herbaceous perennials. In August one might be surprised by ironweed (Vernonia noveboracensis):
A bold rebellious purple,
solitary against the masses
of late-summer trailside yellow,
frugal regality misplaced among commoners.
So we honor it with gathering
and place it in sunny corners
to sharpen our lives,
to delay autumn's somnolence
and December's black days.
I would be very surprised since Cape Ann is out of ironweed's range according to distinguished authorities. Look anyway and enjoy the poem.
The fourth type of forest in Dogtown Common is the plantation white pine and red pine (Pinus resinosa) established by Frederick Norton in the northwest corner of the Common. Now the Norton Memorial Forest, the pines are 35-45 years old and in reasonably good condition. The red pine is especially impressive. White pine plantings in the region have commonly been attacked by the white pine weevil (Pissodes strobi), which kills shoot tips causing multiple-branched tops. Much of Professor Norton's planting appear to have grown free of this pest. An understory of shade tolerant hardwoods and shrubs is developing under these good plantations. But don't worry, it will be many years before the hardwoods succeed them.
In general Dogtown Common forests are recovering well from their 300 years of abuse.
They are modestly diverse due to variable site conditions, especially their wetlands. But they probably don't contain the "5000 varieties of plants" noted by some writers, unless one includes all fungi, algae, lichens and mosses. ("Variety" usually refers to a horticultural product or genetic variant within species, and probably isn't an applicable term here.) Nor do Dogtown forests represent wilderness. One can walk out to a road or a railroad from anywhere on the area in less than an hour, even without a trail - a little longer with a broken ankle. However, they do offer good hill walking, an old forester's ultimate compliment.
They have already been offered by literature I cited above. In brief, carry a compass, map, water, high-priced energy bars, first aid kit and insect repellant appropriate to the season; wear lightweight sturdy, well-fitting shoes good for rock hopping. And don't forget snacks for the ghost dogs. According to the authoritative newenglandfolklore.blogspot there are also werewolves, which probably require larger offerings. On March 17, 1984, a full moon night, two teens on Dogtown Road saw a "gray monstrous dog-like animal running into the woods. It had big teeth and was foaming at the mouth". Who could ask for better evidence. The New England Ghost Project (neghostproject.com) has also recently checked the place out for spectral remains of witches. (For details of Dogtown's sordid occupation history see the books I've cited above.) One of their investigators "psychically experienced the seediness of the town", and felt the "depravity of some of its inhabitants". Moreover, the place has long been known to "be a dead zone where equipment falters and a deadly silence shrouds the forest". I experienced this at dusk on a misty day in the maze of trails near Dogtown Square. I turned around twice, then faced south with the faultless sense of direction acquired during my sixty years in the bush. When I casually looked at my trusty Silva compass, the North end of the needle pointed south. Clearly the witch ghosts were playing with me. I turned around several times to confuse them, my compass read true, and I barely escaped the area before dark. Beware!