The chokeberries (Aronia) are two species of deciduous shrubs in the family Rosaceae, native to eastern North America and most commonly found in wet woods and swamps. The two species are readily distinguished by their fruit color, from which the common names derive. The leaves are alternate, simple, and oblanceolate with crenate margins and pinnate venation; in autumn the leaves turn a bold red color. Dark trichomes are present on the upper midrib surface. The flowers are small, with 5 petals and 5 sepals, and produced in corymbs of 10-25 together. Hypanthium is urn-shaped. The fruit is a small pome, with a very astringent, bitter flavor; it is eaten by birds (birds do not taste astringency and feed on them readily), which then disperse the seeds in their droppings. The name "chokeberry" comes from the astringency of the fruits which are inedible when raw.
Aronia is closely related to Photinia, and has been included in that genus in some classifications (Robertson et al. 1991).
Red chokeberry, Aronia arbutifolia, grows to 2-4 m tall, rarely up to 6 m. Leaves are 5-8 cm long and densely pubescent on the underside. The flowers are white or pale pink, 1 cm diameter, with glandular sepals. The fruit is red, 4-10 mm diameter, persisting into winter.
Black chokeberry, Aronia melanocarpa, tends to be smaller, rarely exceeding 1 m tall, rarely 3 m, and spreads readily by root sprouts. The leaves are smaller, not more than 6 cm long, with terminal glands on leaf teeth and a glabrous underside. The flowers are white, 1.5 cm diameter, with glabrous sepals. The fruit is black, 6-9 mm diameter, not persisting into winter.
The two species can hybridise, giving the Purple Chokeberry, Aronia x prunifolia. Leaves are moderately pubescent on the underside. Few to no glands are present on the sepal surface. The fruit is dark purple to black, 7-10 mm in diameter, not persisting into winter.
The chokeberries are attractive ornamental plants for gardens. They are naturally understory and woodland edge plants, and grow well when planted under trees. Chokeberries are resistant to drought, insects, pollution, and disease. Several cultivars have been developed for garden planting, including A. arbutifolia 'Brilliant', selected for its striking fall leaf color, and A. melanocarpa 'Viking' and 'Nero', selected for larger fruit suitable for jam-making.
Juice from these berries is astringent and not sweet, but high in vitamin C and antioxidants. The berries can be used to make wine or jam after cooking. Aronia is also used as a flavoring or colorant for beverages or yogurts.
The red chokeberry's fruit is more palatable and can be eaten raw. It has a sweeter flavor than the black species and is used to make jam or pemmican.
The plant produces these pigments mainly in the skin of the berries to protect the pulp and seeds from constant exposure to ultraviolet radiation. By absorbing UV rays in the blue-purple spectrum, pigments filter intense sunlight and thereby have a role assuring regeneration of the species. Brightly colorful pigmentation also attracts birds and animals to consume the fruit and disperse the seeds in their droppings.
Anthocyanins not only contribute toward chokeberry's astringent property (that would deter pests and infections) but also give Aronia melanocarpa extraordinary antioxidant strength that combats oxidative stress in the fruit during photosynthesis.
A test tube measurement of antioxidant strength, the oxygen radical absorbance capacity or ORAC, demonstrates chokeberry with one of the highest values yet recorded -- 16,062 micromoles of Trolox Eq. per 100 g (see this ORAC reference for antioxidant scores for 277 common foods). There is growing appreciation for consumers to increase their intake of antioxidant-rich plant foods from colorful sources like berries, tree or citrus fruits, vegetables, grains, and spices. Accordingly, a deep blue food source such as chokeberry yields anthocyanins in high concentrations per serving, indicating potential value as a functional food or nutraceutical.
Analysis of anthocyanins in chokeberries has identified the following individual chemicals (among hundreds known to exist in the plant kingdom): cyanidin-3-galactoside, epicatechin, caffeic acid, quercetin, delphinidin, petunidin, pelargonidin, peonidin and malvidin. All these are members of the flavonoid category of antioxidant phenolics.
For reference to phenolics, flavonoids, anthocyanins and similar plant-derived antioxidants, Wikipedia has a list of phytochemicals and foods in which they are prominent.