Cercis is a genus of roughly ten species of small deciduous trees and large shrubs belonging to the subfamily Cercidoideae within the pea family Fabaceae, order Fabales. Commonly known as redbuds in North America and as the Judas tree in Europe, members of the genus are prized for their spectacular early-spring floral display: dense clusters of pinkish-red to magenta blossoms emerge directly on bare branches and even the trunk — a behaviour called cauliflory — well before the leaves unfurl.
The leaves are simple, rounded to heart-shaped, and arranged alternately along the stems. Fruits are flat, dry seed pods whose shape resembles a weaver's shuttle — the source of the genus name, from the Greek κερκις (kerkis), a term applied by the ancient botanist Theophrastus to Cercis siliquastrum.
The genus ranges across warm temperate regions of the Northern Hemisphere: eastern and western North America (from southern Canada south to Alabama and Texas, and west to California and Utah), southern Europe (the Iberian Peninsula, France, Italy, Greece, and the Balkans), western and central Asia, and China. Fossil evidence places the lineage in the Eocene, and molecular phylogenetic studies of the North American species reveal at least three geographically coherent clades that began diverging roughly 12 million years ago.
Notable members include the eastern redbud (Cercis canadensis), one of the most widely planted ornamental trees in North America; the Judas tree (Cercis siliquastrum) of southern Europe and southwest Asia, whose edible magenta flowers have appeared in herbals since the 16th century; the western redbud (Cercis occidentalis) of California foothill woodlands; and the chain-flowered redbud (Cercis racemosa) of western China, unique in the genus for bearing its flowers in pendulous racemes up to 10 cm long rather than the short lateral clusters typical of the genus.
Etymology
The genus name Cercis derives from the ancient Greek κερκις (kerkis), meaning "weaver's shuttle." The Greek botanist Theophrastus applied this term to Cercis siliquastrum because its flat, elongated dry seed pod closely resembles the shuttle used on a loom.
Distribution
Cercis is native to warm temperate regions of the Northern Hemisphere, with species occurring across eastern and western North America (from southern Canada south to Alabama and East Texas, and west through the Colorado Plateau to California and Utah), southern Europe (including the Iberian Peninsula, France, Italy, Greece, and the Balkans), western and central Asia, and China. The North American species form three molecularly distinct clades corresponding to the eastern, Colorado Plateau, and Californian geographic regions.
Ecology
Cercis species are larval host plants for certain Lepidoptera, including the mouse moth and the io moth (Automeris io), both recorded feeding on eastern redbud (C. canadensis). The early-spring flowers appear before the leaves and are an important nectar source for pollinators emerging in late winter and early spring.
Cultivation
Redbuds are widely cultivated as ornamental trees in temperate gardens. Cercis canadensis is among the most popular spring-flowering trees in North American horticulture, valued for its precocious pink bloom, attractive heart-shaped foliage, and modest size. Cercis siliquastrum is similarly grown across European gardens. White-flowered variants of Cercis occidentalis are also in cultivation. The genus generally thrives in well-drained soils and full sun to partial shade, and tolerates drought once established.
Cultural Uses
Flowers of Cercis siliquastrum and Cercis canadensis are edible — eaten raw in mixed salads, made into fritters with an agreeably acidic flavour, or used to make pickled relish. The inner bark of C. canadensis twigs yields a mustard-yellow dye. The bark of C. chinensis has a long history of use in Chinese traditional medicine as an antiseptic. Cercis siliquastrum holds cultural and religious significance in European tradition as the tree from which Judas Iscariot is said to have hanged himself, though the name may alternatively derive from "Judea's tree," after the region where it grows abundantly.
History
Cercis fossils date to the Eocene, indicating the genus has a long geological history. Cercis siliquastrum was a subject of considerable botanical interest in the 16th and 17th centuries and was frequently illustrated in the herbals of that era. Taxonomic circumscription of the North American species has been debated since at least the 1940s, with different authorities recognising anywhere from one to six species on the continent; molecular phylogenetic data now support three distinct North American species.
