General Description The Arboretum is blessed with a variety of forest types commonly found in central New England. The entire site was at one time (or repeatedly) totally clear-cut and converted over to annual crops, orchard, or pasturage, as is the predominating factor in most of eastern Massachusetts. With the exception of a very few large white oaks (Quercus alba), virtually all the trees found in the Arboretum are fairly recent re-growth and are less than one hundred years old. Considering that Massachusetts was 90% deforested as recently as 1900, the situation in the Arboretum is not at all unique.
Approximately 35% of the present Arboretum consists of old apple (Malus pumila) orchards that were colonized with other species. The remainder of the Arboretum was used for pasturage or had been orchard so long ago that no apple trees remain. The former pasturage areas have become colonized with a fairly diverse assortment of native species (and a few non-native such as glossy buckthorn and multiflora rose) typical of this part of the Commonwealth. The various forest types are in fairly cohesive blocks that relate directly to former land use patterns or to the underlying geology and hydrology. This inventory has identified no less than ten distinct forest types that can be observed by even the casual viewer in walking about the trail system.
General Observations and Suggestions
Each area is inventoried below. Some management issues and alternative solutions have been suggested to be considered as part of the development of an overall Arboretum plan.
Considering the central location of the parcel, the high public use, and the progressive nature of the development of the “formal” areas of the Arboretum, this inventory emphasizes the landscape, aesthetic, wildlife, and educational values of the parcel, rather than the economic predisposition of a traditional inventory.
Most of the forest in the Arboretum is of fairly low value from a harvesting point of view. With the exception of several white pine (Pinus strobus) stands, there is very little standing timber worth harvesting other than in conjunction with a timber stand improvement plan focused on eventual upgrade and timber production. While timber stand improvement for production is not a main goal of a plan that places an emphasis on aesthetic, recreational and wildlife values; stand improvement designed to improve long-term health and diversity is a viable goal.
Most hardwood harvesting programs emphasize removal of large "wolf" trees that absorb an overabundance of solar resources, or the cutting of "really nice" trees that have significant saw log value. Those objectives are in conflict with the overall vision and values of the Arboretum, which encourages the retention of large and unique trees as valuable components of the Arboretum inventory.
Individual Area Inventories
The Arboretum has been divided into 11 areas for the purpose of this inventory.
Area One (Formal Arboretum Collection) 6+/- Acres
Area One is bounded by Taylor Road, Main Street, the Arboretum parking area, the wildlife pond, and the drainage ditch (boundary of the abutting property.) The area was formerly an apple orchard. A few specimens remain. This area comprises most of the "formal" Arboretum and is not specifically addressed in the forest inventory, but is dealt with in the other sections. It includes the Swale and Pond Plantings, Crabapple Allee, Daylily Collection, Hosta, Herb and Butterlfy Gardens.
Area Two (Old Orchard) 9.5+/- Acres:
Area Two is located to the east of the formal Arboretum, just over the drainage ditch, and is bounded to the north by the White's property, and to the east by the shallow farm ponds and drainage ditch. The area is representative of what the formal Arboretum area looked like prior to development in the late 1980s. There are a few old apple trees and most of the groundcover consists of grasses, forbs, poison ivy (Rhus radicans), gray dogwood (Cornus racemosa), and multiflora rose (Rosa multiflora). The wet areas contain a number of pole size American elms (Ulmus americana), unfortunately several of which have contracted Dutch elm disease (Ophiostoma novo-ulmi).
The most significant aspect of this area is its function as a 'natural nursery' for other plants to seed. The most important of these introductions are a number of black walnuts (Juglans nigra) that are between 6 and 12 inches DBH (diameter-at-breast height) and between 20 and 30 feet high.
Some black walnuts should be retained, pruned, and developed as landscape specimens especially since they are close to the collection of other nut-bearing trees. It should be noted that black walnut releases Juglandin, a powerful phytotoxin into the soil, which inhibits the growth of competitive plants within the root system. Thus it is not advised to introduce understory plantings into proximity with the walnuts.
Area Three (Wet Upland Mixed Hardwood Forest) 9.5 Acres:
Area Three is located at a slightly higher elevation, east of the old farm ponds between elevations 230 and 250 on a west facing slope. The area is bounded to the east by the old orchard, behind the residences on Wood Lane and to the south by a large pine stand and the recently cleared field (Area Four).
Area three is characterized by shallow soils and high groundwater with many exposed rocks. The forest is dominated by fairly large hardwoods, with a few isolated pines. The largest specimens consist of red maple (Acer rubrum), white ash (Fraxinus americana), sugar maple (Acer Saccharinum), red oak (Quercus rubra), and white oak (Quercus alba). The canopy is tightly closed with the largest trees exceeding sixty feet in height and diameters ranging from 14 to 30 inches.
Species composition is roughly 30% maple, 30% ash, 30% oak, with the remainder assorted. Of note is the presence of European spindle-tree (Euonymus europaeus) and yew (Taxus sp.) in the understory and the abundance of the native and highly desirable sugar maple (Acer saccharum).
American beech (Fagus grandifolia) could be introduced into this area. The area could also be used as a sugar bush demonstration plot. Other maple species that would make good understory species such as striped maple (Acer pensylvanicum) could also be introduced.
As this area progresses to the south towards the meadow and the pine stand, the ground gradually becomes somewhat drier; and there are a number of quite large white oaks (Quercus alba) on either side of the trail. The most significant oak, located between two trails, has an almost druidic feel to it as it stands in the forest. These oaks are probably the largest specimens in the Arboretum with diameters of 30 to 40 inches and heights of 50 to 60 feet and are some of the oldest trees in the parcel. They date back over one hundred years to when the area was open pasture. These large oaks are located very near the stonewalls.
Area Four (Meadow) 2.5 Acres:
Area Four is located between the large pine stand and the large rock outcropping behind the residences at the very end of Wood Lane. Historically, it was an apple orchard that was colonized by a variety of oaks and more pervasively by staghorn sumac (Rhus typhina), common buckthorn (Rhamnus cathartica), and quaking aspen (Populus tremuloides).
In the northeast corner, there is a very steep exposed ledge that is topped with junipers (Juniperus communis). At the base of the ledge is a small cluster of tupelo (Nyssa sylvatica) that are approximately 8 inches DBH and 30 feet high. Tupelo is fairly rare in Acton, thus these specimens should be preserved. Tupelo is generally considered to be a wetlands species, tolerant of flooding. It appears that there is a small seep or spring at the base of the ledge, which provides a constant water supply for both the tupelos and the American cranberrybush (Viburnum trilobum) which is immediately adjacent to the tupelos.
The balance of this area was cut over in 1996-1997, with only a few red oak (Quercus rubra) white oak (Quercus Alba) and pignut hickory (Carya glabra) specimens preserved.
Area Five (Old Orchard) 2.5 Acres:
Area Five is located to the east of Area Three (Wet Upland Mixed Hardwood Forest) and to the west of the residences on Wood Lane. North of this area is the property boundary, and to the South is Area Four (Meadow). As is the case with many parts of the Arboretum, this is an old apple orchard with fairly high ground water. There are a number of very large old apple (Malus pumila) trees in this area, that are hollow and in advanced stages of decline. Many of the apples are overrun with poison ivy (Rhus radicans) with vines over two inches in diameter.
There are a few white ash (Fraxinus americana) in this area and some pin cherry (Prunus pensylvanica) and choke cherry (Prunus virginiana.) However, the most dominant species is Morrow honeysuckle (Lonicera x morrowii). This invasive shrub has monopolized much of the open area of this parcel, often becoming the dominant understory species. With effort, it can be eradicated, and it probably will need to be eradicated in some areas.
Area Six (White Pine Stand) 4 +/- Acres:
Area Six is located due south of the Wet Upland Mixed Hardwood forest and to the west of the Meadow. This area is the beginning of a fairly well defined ridge or esker that runs north - south through the southern portion of the Arboretum.
The white pines (Pinus strobus) range in diameter from 11' to 20' DBH with a few larger trees that are in poor shape. Heights of the trees are approximately 70 feet, and the estimated age of the larger trees is around 75 years. A number of these trees have been damaged over the years, and a few have died due to lack of sunlight.
Area Seven (Dry Upland Mixed Forest) 4+/- Acres:
Area Seven is bounded to the north by the Wet Upland forest and the Meadow and to the south by the Red Maple Swamp (Area Eight) and the bog. The forest was created by the colonization of the very distinct esker that runs north-south, bounded on both sides by wetlands. The esker is composed of extremely well-drained gravel and sand and the vegetation types reflect that fact.
The Highland-Bog Loop trail runs along the fairly narrow top of the esker, and the hiker can see a wide variety of trees that are adapted to dry conditions. This is very interesting since these trees are located laterally less that 100 feet from species that can only survive in the most waterlogged soils.
The general composition of this Dry Upland Mixed forest is approximately 30% white pine (Pinus strobus), 30% red oak (Quercus rubra), and the balance composed of a wide variety of species, including a few pitch pines (Pinus rigida), which are very uncommon in Acton. Other species include black birch (Betula lenta), gray birch (Betula populifolia), white ash (Fraxinus americana), American chestnut (Castanea dentata), which succumbs to the chestnut blight when still pole sized, and pignut hickory (Carya glaba.)
Area Eight (Red Maple Groundwater Slope Wetland) 3 Acres:
Area Eight is located to the south of the Dry Upland Mixed forest and to the north of, and slightly uphill of, the bog. It is less than three acres in size and was once an apple orchard, of which a few very debilitated apples trees remain.
The very high groundwater, which in rainy periods flows overland into the bog, has caused this area to become a hillside of red maple (Acer rubrum), basically a thicket with a completely closed canopy. Most of the maple stems range from 6 to 12 inches DBH with heights ranging up to 40 feet. Due to the shady, wet ground conditions, there are very few competing species. The red maple constitutes over 90% of the woody species.
Area Nine (Bog) 3.5 +/- Acres:
The bog is located at the southern extremity of the present Arboretum and is bordered to the South by Minot Avenue. The bog is a classic glacially created wetland that has been colonized with bog plants.
Red maple (Acer rubrum) has encroached onto the bog. Several years ago during the winter, town staff elimnated many maple stems in an attempt to arrest the progression on the bog into a red maple swamp. Due to the unique ecosystem reflected by the bog, this management practice should continue in the future.
Area Ten ( Upland Mixed Forest) 8+/- Acres:
Area Ten is located to the south of the Meadow and is bisected by the fire lane running to the dead end of Wood Lane. Approximately 80% of the trees in this area are white pines (Pinus strobus), with the remainder a mixture of white oak (Quercus alba), red oak (Quercus rubra), white ash (Fraxinus americana), and red maple (Acer rubrum). One of the most striking aspects of this area is the very clear delineation between the pine stand and the neighboring open areas that had been orchards in the past.
The pine component ranges in diameter from 12 to 30 inches DBH with heights ranging upwards to 70 feet. These trees have never been pruned or thinned, and most have dead branches on the stem down almost to grade level. At present the pines have very little value for timber, but represent good wildlife habitat.
The mixed hardwoods range in diameter from 8 inches to 20 inches DBH and are as tall as the neighboring pines. There are several small openings caused by wind-thrown trees that are beginning to regenerate with young white pines, now standing 6 to 8 feet in height. Some of these pine thickets could be thinned and up-branched to eventually create a traditional pine stand.
Area Eleven (Dry Upland Field) .75 +/- Acres:
Area Eleven is somewhat separated from the balance of the Arboretum because it is located to the east side of Wood Lane. The Town has acquired an easement associated with “Concord Place” thus, this parcel is now a significant access point between the Arboretum and Concord Road.
Most of this area was once apple orchard, and a few somewhat debilitated apple trees are still present. Several years ago approximately one half acre was cleared in an effort to maintain some open area, and it was treated in a similar fashion to the Meadow in Area Four, the exception being that the stumps were treated with herbicides so that they did not re-sprout. Thus, the area is somewhat self-perpetuating and needs only occasional mowing to control blackberry vines. As is the situation in Area Four, a few specimen oaks and hickories were preserved. The balance of the area consists of a sloping dry upland forest, consisting of mostly oak (Quercus sp.), hickory (Carya glaba), and white pine (Pinus strobus) ranging from 6 inches to 20 inches in diameter DBH with an understory in the field edges of staghorn sumac (Rhus typhina) and common juniper (Juniperus communis.)