From Christmas decorations to classic holiday songs like “Deck The Halls,” holly is a traditional part of the Christmas season. It’s pointy-edged, dark green leaves and bright red berries are commonly used to make festive looking wreaths that adorn doorways and windows this time of year.
Michael Piantedosi, director of conservation for the Native Plant Trust in Framingham, said English holly (Ilex aquifolium), which is native to Europe, was part of the Druid mythological traditions going back at least 2,000 years, and was used in winter solstice celebrations. Holly later became co-opted into Christmas holiday celebrations.
But holly is also a part of forests and other ecosystems in the United States and around the world. There are some 400 different species of holly worldwide, about 15 of which are native to the United States, according to Piantedosi.
Massachusetts has half a dozen native holly species, and a couple of introduced species, said Piantedosi. Perhaps the best known of our native hollies is the American holly (Ilex opaca), a tree that grows from East Texas to northern Florida, and northward to coastal Massachusetts.
In Massachusetts, American holly has been documented growing wild as far north as Essex County on the North Shore, Piantedosi said, and is typically confined to somewhat sandy, acidic soils along the coastal plain. He added that the majority of American holly populations in the state are found along Cape Cod and the south coast of Massachusetts.
In East Falmouth on Cape Cod, Mass Audubon has the Ashumet Holly Wildlife Sanctuary, which is home to some 1,000 American holly trees of 65 varieties.
Ian Ives, director of Mass Audubon’s Mid- and Upper-Cape Wildlife Sanctuaries, said the 45- acre Ashumet Holly sanctuary was gifted to Mass Audubon in 1963 by Josiah Lilly III, who had purchased the property known as Ashumet Farm from Wilfrid Wheeler. Concerned that American hollies on the Cape were being destroyed by military maneuvers and people harvesting hollies for wood and decorations, Wheeler, who became known as the “holly man,” began growing hollies on this property in the 1920s and ’30s.
Ives said aside from American holly there are two other native holly species in the sanctuary — inkberry (Ilex glabra) and winterberry (Ilex verticillata), along with several other nonnative species.
Unlike American holly, which retains its leaves year-round, winterberry is deciduous, meaning it loses its leaves in winter. It is common in wetlands in Massachusetts, where its bright red berries stand out against snowy winter landscapes and the drab brown of leafless winter vegetation.
Ives said Mass Audubon has an annual pubic holly walk at the sanctuary, which will be on Dec. 14 this year.
In the southern part of their range, American holly trees can grow to around 50 feet tall. But in the northeastern part of its range, Piantedosi said, American holly doesn’t usually reach such heights due to winter storms and high winter winds, and commonly occurs as small trees or shrubs, typically about 15 to 25 feet tall. Ives said the tallest American holly at Ashumet Holly Wildlife Sanctuary is 45 feet tall.
Piantedosi said holly berries, technically known as “drupes,” are an important food for wildlife, while the leaves and branches provide shelter for animals.
“American holly is an excellent winter food for overwintering birds, and for songbirds in the spring when the fruits soften a bit,” said Piantedosi. “It is also an excellent cover for nesting birds and small mammals.”
Piantedosi said that according to the US Department of Agriculture, at least 18 species of birds, including mourning doves, wild turkeys, bobwhite quail, cedar waxwings, and goldfinches, are known to eat the fruit of American holly. Deer, squirrels, and other small mammals also eat holly berries.
Ives said cedar waxwings and overwintering robins frequently feed on holly berries at the Ashumet Holly Wildlife Sanctuary.
“They eat the berries whole and deposit seeds in their droppings,” said Ives.
It’s a mutual relationship, Ives said. The birds get food, and the holly trees get their seeds dispersed.
While wildlife may like eating holly berries, Piantedosi emphasized that holly fruit is toxic to humans and most domestic pets.
“The berries of all species of Ilex [holly] are reported to be poisonous if eaten in quantity,” said Piantedosi. “The attractive red drupes should be avoided as symptoms from consumption include nausea, vomiting, and diarrhea.”
Ives said holly flowers are a source of pollen and nectar for wasps, bees, butterflies, and moths, which act as pollinators for holly.
Both American holly and winterberry are popular choices for gardens, said Uli Lorimer, director of Horticulture for the Native Plant Trust.
“American holly is an evergreen and can become a stately tree in time,” said Lorimer. “Winterberry is a shrub and is prized for its display of red fruit during the winter months, its autumn foliage, and the floral resources that it provides to local pollinators.”
Hollies are dioecious, Lorimer added, meaning there are separate male and female plants. In order to produce berries, the female plant must be pollinated by a male plant.
“I have heard folks complain or wonder if they are doing something wrong when their holly does not produce fruit,” said Lorimer. “The answer is usually that they have a male plant and no matter how much they may want fruit, he just can’t do it.”
Don Lyman is a biologist, freelance science journalist, and hospital pharmacist who lives north of Boston. Send your questions about nature and wildlife in the suburbs to firstname.lastname@example.org.