Last updated: September 8, 2021
Article
Grape Island Plants
In a two-year project funded by the Island Alliance to study the vegetation of the Boston Harbor Islands National Park Area, 32 islands were surveyed and inventoried for vascular plant species. Field surveys began on 9 June 2001 and ended on 30 September 2002.
Below is the data collected for Grape Island.
Data Notes:
* = introduced species
(v) = voucher specimen
(p) = photograph
Due to formatting restrictions, species scientific names are not italicized in the data table.
* = introduced species
(v) = voucher specimen
(p) = photograph
Due to formatting restrictions, species scientific names are not italicized in the data table.
| Species_Scientific_Name | Species_Common_Name | Family | Date_Observed | Habitat |
|---|
Notes on Habitats and Flora
Grape Island’s habitats are in healthier condition and support a greater natural plant diversity than almost all of the other islands, except for World’s End. Thickets dominated by shrubs and early successional trees such as gray birch (Betula populifolia), quaking aspen (Populus tremuloides), bayberry (Myrica pensylvanica), and staghorn sumac (Rhus typhina) cover most of the island. In general, western and central sections of the island have woodland thickets with gray birch, aspens, and occasionally black cherry, while the eastern side of the island has shrub thickets dominated by staghorn sumac, bayberry, and wild red raspberry with a thin tree overstory.
Old fields of perennial grasses and forbs are interspersed with woodlands and shrub thickets on the highest parts of the island. Most of these fields are dry, but one field on the island’s north side has enough moisture to support such characteristically wetland species as soft rush (Juncus effusus), woolgrass (Scirpus cyperinus), and several Carex sedges (including C. lurida and C. scoparia). A shaded, moist, red maple (Acer rubrum) woodland with numerous ferns, including sensitive fern (Onoclea sensibilis), cinnamon fern (Osmunda cinnamomea), and marsh fern (Thelypteris palustris) is located on the north-facing slope behind the island’s northern shoreline. Other upland habitats include a lawn near the Grape Arbor, and disturbed openings adjacent to pathways, picnic grounds, and camping sites. “Waste areas” include very dry, sandy and pebbly openings in the vicinity of the dock.
Grape Island has one fairly large wetland complex approximately 500 feet northeast of the dock. This disturbed, depressional area once was a salt marsh, but changes in the configuration of the beach have blocked the infusion of salt water into this low-lying area just behind the beach (Island Alliance 2001). The vegetation now contains species representative of both freshwater and brackish conditions. Common reed (Phragmites communis) covers a large part of this wetland. Other typically “freshwater” species include awl-fruited sedge (Carex stipata), purple loosestife (Lythrum salicaria), marsh bedstraw (Galium palustre), and blue vervain (Verbena hastata). Saltwater species still found in this marsh include black grass (Juncus gerardii) and salt hay (Spartina patens). Mandy Karnauskas (2001) reported that this wetland has one of the most diverse aquatic invertebrate populations of any wetland found on the Harbor Islands.
A smaller, more natural freshwater wetland is located just behind (south) of the beach on the north side of the island. This small area has masses of sensitive fern (Onoclea sensibilis) and a small population of blue flag (Iris versicolor). This wetland, which was found at the end of the 2001 field season, should be surveyed more thoroughly in 2002.
Beach strand vegetation occurs around the perimeter of the island. Characteristic plants include orache (Atriplex patula), lamb’s quarters (Chenopodium album), beach-pea (Lathyrus japonicus), saltwort (Salsola kali), and tall seablite (Suaeda linearis).
The seabeach dock (Rumex pallidus) population, which was first documented on Grape Island in 1897, is located along the high tide line on the west side of the island. Most of this vigorous population, which in 2001 contained approximately 55 fruiting stems and 25 vegetative stems, is densely clustered. A single anemic-looking plant consisting only of basal leaves is located about 200 feet south of the main cluster. Grape Island’s seabeach dock population has been stable since the Massachusetts Natural Heritage and Endangered Species Program started tracking it in 1982.
Earlier plant surveys on Grape Island include inventories by Levering (1978), Perkins (1985), and island naturalists whose 1980’s plant observations are summarized in Perkins’ paper.