Forests are one of Maine’s most beloved plant communities. In some of these forests, various species of oak dominate the canopy alongside other trees—understandably, they are called Oak Forests. These communities are found on gentle slopes in moderate or dry areas. The soil is well-drained, sandy, acidic, and quite shallow. Most of these forests occur on land that was once pasture or cleared for timber harvesting, and they are now found in small, fragmented patches due to continued farming, timber harvesting, or residential development. In these types of forests, fire may have once played a role in regeneration for certain species, specifically Eastern White Oak and Shagbark Hickory.
Oak Forests have mostly or entirely closed canopies. Alongside dominant Northern Red Oak, Eastern White Oak, and Black Oak, other common trees include Shagbark Hickory and Eastern White Pine. Less frequent trees such as maples, birches, beeches, and hemlocks may also pepper the landscape. Beneath this canopy layer, some tall shrubs or small trees such as Witchhazel, Serviceberry, Striped Maple, and Mapleleaf Viburnum can be found. The ground may have some sparse herbaceous species like Bracken Fern, Wild Oats, and Cucumber Root, or it can be covered in sedges and grasses, often Woodland Sedge. Lowbush Blueberry is a frequent woody groundcover, and these forests are also habitat for extremely rare plants such as Wild Indigo and Sundial Lupine.
Oak Forests make perfect habitat for a number of songbird species, including Scarlet Tanagers, Whippoorwills, and Pine Warblers. Ground foragers like Ovenbirds and Wood Thrushes require wooded habitats like these to search for insects on the forest floor. Older, mature trees provide habitat for cavity nesters such as Flying Squirrels. Northern Red Oaks are also the host plant for the rare Red-winged Sallow Moth.
Here are three plants and their features to look for in Oak Forest plant communities:
Northern Red Oak
Northern Red Oaks are the most common oak tree in Maine, and they make up a large percentage of canopy trees in these forest communities. They are fast-growing and can reach up to 120 feet, and they can live up to 400 years! As opposed to other oaks, Northern Red Oak bark has light vertical striping down the center of its ridges. The leaves are dense and alternating on the branches, each with 7-9 broad, pointed lobes. The newly emerging leaves are pinkish in spring, turn deep and waxy green in summer, and become red to copper brown in fall. This is where the name “Red” comes from, in addition to red leaf petioles and reddish wood. The acorns are round and take two years to develop. Nut production is regular most years, but every 2-5 years these oaks have a “mast year.” This is when trees produce many more nuts than usual, flooding the landscape and overwhelming foragers. Because animals are unable to eat all the acorns, nut survival increases and new trees can develop!
Although edible, raw acorns are very bitter due to their tannins. However, they can be processed to make them more tasty! Indigenous peoples frequently boil and leach the tannins from these nuts, then crush them into acorn flour. Northern Red Oaks also make excellent timber, which is used for lumber, flooring, furniture, and fences. They also serve as a landscape or urban tree, offering wonderful shade because of the density of their leaves.
Northern Red Oaks and other oak trees support the highest number of caterpillar species, with current counts indicating 431 different species! Of course, the acorns are also a huge food source for many birds and mammals, especially in winter. Rabbits, deer, and moose browse the foliage, and deer browse buds and twigs in winter. These trees also provide abundant cover and nesting sites for birds and mammals.
Shagbark Hickory
Shagbark Hickory is named after and easily identified by its light gray bark that peels and curls away in large plates that are barely attached to the tree. This characteristic is very unique to this exact species of hickory! The word hickory itself is derived from the Algonquian word Pawcohiccora, which refers to the nut. The nuts are pale white with a thick, dark brown husk that splits open in four sections when ripe. Shagbark Hickory leaves are compound, with 5-7 leaflets contained in one leaf. The leaves are very finely toothed and turn brilliant yellow in the fall. This tree can grow up to 80 feet tall.
Indigenous peoples savor the nuts, pounding them into a paste and sometimes adding water to make hickory milk. They also use the sturdy and flexible wood to make hunting bows and axe handles. Historically, hickory wood was also used to make wagon wheels, and current uses include skis, tool handles, furniture, and flooring. It is also one of the best choices for firewood, which often lends itself to the iconic hickory-smoked flavor for bacon and ham! Hickory syrup can also be made from the sap.
Shagbark Hickory is a food plant for many insects, including borers, aphids, treehoppers, and stinkbugs. The catkins are eaten by birds and squirrels, who also enjoy the delicious hickory nuts. The curved and loose panels of bark are particularly excellent roosting habitat for bats and Brown Creepers!
Switchgrass
Switchgrass is one of the many grasses that can be found in Oak Forests, but it is also common in meadows and on roadsides throughout most of the U.S. It is clump-forming and grows up to 5 feet tall with even deeper roots. The stalks are stiff and upright, giving it the appearance of a switch—hence the name. The leaves fade to pale yellow in fall, timed perfectly with the development of feathery, red to purple seed heads, making Switchgrass a beautiful sight in the fall. To identify this plant, look for the very subtle tufts of white fuzz on the leaf where it attaches to the stem.
Switchgrass is commonly used in restoration projects due to its drought tolerance, flood tolerance, deep roots for erosion control, and height for a windbreak. It is a great crop for pasture, hay, and straw. The tall and sturdy foliage of Switchgrass makes excellent nesting habitat and cover for pheasants and rabbits, especially in winter where it holds up against heavy snow. Many birds will eat the seeds throughout fall and winter as well. This grass is the exclusive host plant for a handful of Lepidoptera: the Black-bordered Lemon Moth, Hobomok Skipper, Northern Brokendash, and Tawny-edged Skipper.
Switchgrass is also being considered as a biofuel crop—over $100 million has been invested in research for this to lessen our dependence on fossil fuels. This grass produces a high energy yield, even better than corn, and it is quite hardy and easy to manage. Currently, it seems to have the best potential for being made into pellets that can be burned to heat homes or fuel coal power plants.
