When planted in full sun and moist, acidic soils, this groundcover is a low-maintenance source of food, beauty, and wildlife value. The trailing evergreen shrub spreads by rhizomes to form a dense mat of petite, glossy leaves that are never idle, changing from a bronzy hue in spring to dark green in summer, while in fall, the colors range from copper to purple. The petite, pink flowers are followed by reddish-pink fruits that are sold commercially for their tart flavor. Classified as an obligate wetland plant, meaning it almost always occurs in wetlands, large cranberry is a common species in acidic bogs of Ohio, excepting the western part of the state. The roots should be kept cool and moist, and the soil pH should be less than 6 or the plant may be subject to chlorosis. However, this plant tolerates compacted soils.

Large cranberry (V. macrocarpon) and the similar-looking small cranberry (V. oxycoccos) are the sole host plants for the caterpillars of bog copper butterfly (Lycaena epixanthe), which has a fascinating life cycle that only occurs on cranberry plants in bogs or wetlands and, less frequently, in wet, acidic meadows or ditches. Commercial cranberry bogs are treated with insecticides, which further decreases the available habitat for this specialized insect. Bog copper is perfectly adapted to wet conditions. The female deposits single eggs at the base of the cranberry plant, and a layer of air under the outer skin allows the egg to develop while under water. It remains dormant for almost a year until the caterpillar, which is similarly adapted to wet environments, emerges and feeds on cranberry leaves. The mature butterflies take nectar primarily from cranberry blossoms and are likely important pollinators of cranberry plants. Read more about bog coppers in mytimes.com (https://rb.gy/t41duh).

Another common name for large cranberry is bearberry, probably due to the plant's resemblance to another "bearberry" in the same family that produces fruits with a more mealy texture (Arctostaphylus uva-ursi). Large cranberry is distinguished from small cranberry by its larger, flatter leaves with more-rounded tips and a pair of floral bracts midway or lower on the flower stalk.

Plant Characteristics:

Grows 2-6" tall and spreads to form mats.

Prefers full sun and adapts to dappled shade, which results in fewer fruits.

Prefers moist to average, well-drained, acidic soils and tolerates occasional flooding.

Blooms appear May-July as 2-6 pinkish-white flowers on long stalks. Flowers are 1/4 - 3/8" long with 4 lance-shaped petals that curl sharply upwards. Projecting from the center is a tight cluster of long, slender, reddish stamens and a single, slender style that is longer than the stamens. Round, 1/2" fruits ripen August-November.

Reproductive System: flower contains both male and female parts (perfect/bisexual) and is self-fertile, although the flower structure discourages self-fertilization. Pollination by insects and wind greatly improves fruit production.

Wildlife Value:

Host plant for 223 species of Lepidoptera larvae, including the beggar, crocus geometer and Polyphemus moths; red-spotted admiral butterfly; and specialist Cerastis fishii. Berries are eaten by birds and small mammals. Members of the genus Vaccinium support the following specialized bees: Andrena bradleyi, Andrena carolina, Panurginus atramontensis, Habropoda laboriosa, Colletes productus, Colletes validus, and Osmia virga.

Medicinal, Edible, and Other Uses:

Cranberries have long been a food source for Native Americans. A growing body of research suggests that the polyphenols found in our native cranberries may be important in reducing the risk of cardiovascular disease. The fruits are also rich in vitamin C.

The raw fruits are too acidic for most people, so they are dried or used in preserves, pies, and savory dishes. One source suggests adding a teaspoon of salt to stewing fruits to take the place of half the sugar normally used.

Resources:

Lady Bird Johnson Wildflower Center

https://www.wildflower.org/plants/result.php?id_plant=VAMA

Minnesota Wildflowers

https://www.minnesotawildflowers.info/shrub/large-cranberry

Plants for a Future

https://pfaf.org/user/plant.aspx?latinname=Vaccinium+macrocarpon

National Wildlife Federation

https://nativeplantfinder.nwf.org/Plants/3423

North Carolina Extension

https://plants.ces.ncsu.edu/plants/vaccinium-macrocarpon/

Pennsylvania Natural Heritage