Mast Year

As the days get cooler and frost is in the air, the colorful flora display is spectacular with the changing leaves and abundance of berries, nuts, and seeds. On a hike in the White Mountains, your eyes will be drawn to the mountain ash, hobblebush, bunchberries, blue beaded lilies, and cones that litter the forest floor. This year marks an abundant mast year for many local plants, with a wealth of berries, nuts, and seeds. Mast year is most easily defined by the amount of nuts, seeds, and fruit that a woody plant provides for the local wildlife. The high levels of fat and protein in fall mast contributes to fat stores necessary for migration, hibernation, and survival of the independent young.


If you have hiked into the boreal forest zone at 3500ft I am sure that you noticed the balsam fir and red spruce cones. Balsam fir is the preferred food for spruce grouse and browsing for deer and moose. The red spruce provides seeds for red squirrels and makes up 25-50% of the white-winged crossbills diet. Mountain Ash, which is found in both the Northern Hardwood forest and in the Boreal forests provides fruit for ruffed grouse, jays, American robin, thrushes, waxwings, red squirrels, and rodents.

Mountain Ash

There are over 120 trees and shrubs in New Hampshire that produce mast used by wildlife. Masting is a natural cycle that produces low or moderate crops most years and an abundant crop once every two to five years. Several factors determine whether the season will allow for a large mast: weather, genetics, tree dominance, and mast predators. To maximize mast production of trees, they must be allowed to attain optimum age and diameter required. For example, the optimum age for beech trees is >60 years with 14” dbh (diameter breast height), >50 years with 14” dbh for ash and maples, and 30-100 years with 10” dbh for cherry trees. Hard mast producing trees with mast available to wildlife currently include: beech, oak, sugar maple, mountain ash, cherry, pine, oak, hemlock, fir, and cedar. Shrubs with mast available to wildlife currently include: june-berry, mountain holly, hobblebush, high-bush cranberry, blueberry, raspberry, elderberry, twisted stalk, bilberries, and bunchberry.

Twisted Stalk

Some of the species discussed in this blog are part of our Mountain Watch Program and can be followed on

-H. Cowan
AMC Naturalist Guide