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Heath Family (Ericaceae)

Species In North America, Economic Importance

The heath family, or Ericaceae, contains about 100-125 genera of vascular plants comprising 3,000-3,500 species. These plants are widespread in North and South America, Eurasia, and Africa, but are rare in Australasia. Species of heaths are most diverse and ecologically prominent in temperate and subtropical regions.

The most species-rich genus in the heath family are the rhododendrons (Rhododendron spp.), of which there are 850-1,200 species. The exact number is not known because species are still being discovered in remote habitats, and because the taxonomy of these plants is quite difficult and somewhat controversial among botanists. The "true" heaths (Erica spp.) are also diverse, containing 500-600 species. The blueberries and cranberries (Vaccinium spp.) include about 450 species, a few of which are cultivated for their fruits.

Plants in the heath family are woody shrubs, trees, or vines. Their leaves are simple, usually arranged in an alternate fashion along the stem, and often dark-green colored. The foliage of many species is sometimes referred to as "evergreen," meaning it persists and remains functional in photosynthesis for several growing seasons. Other species have seasonally deciduous foliage. The flowers are radially symmetric, and are perfect, containing both staminate and pistillate organs. The fused petals (most commonly five in number) of many species give their flowers an urn- or bell-shaped appearance. The flowers may occur singly, or as inflorescences of numerous flowers arranged along the stem. The flowers of most species of heaths produce nectar and pleasant scents, and are pollinated by insects such as bees and flies. The fruits are most commonly a multi-seeded berry, a single-seeded drupe, or a capsule.

Species of heaths typically grow in acidic, nutrient-impoverished soils. Habitats range from closed to open forests, shrub-dominated communities, bogs, and tundras. All species of heaths have a heavy reliance on mycorrhizal fungi to aid in the acquisition of mineral nutrients, especially phosphorus.

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Science EncyclopediaScience & Philosophy: Habit memory: to Heterodont