Asteraceae

Bidens flwr

Leucanthemum diagram

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Carduus floral diagram

Senecio mikanioides (delairea odorata)

Senecio angulatus flowers

Asteraceae or Compositae is a large and widespread family of flowering plants. With more than 32,000 species distributed across 1,911 genera, it is the largest family of flowering plants in terms of the number of species. The family is commonly referred to as the aster, daisy, composite, or sunflower family. Members of this family can be found in nearly every habitat, including gardens, meadows, and mountainous areas, across all continents except Antarctica.

Characteristics

Asteraceae are characterized by composite inflorescences called capitula, commonly mistaken as single flowers. The capitula are composed of multiple individual flowers, or florets, arranged on a receptacle. The family is distinguished by having both ray florets, which are typically sterile and serve to attract pollinators, and disc florets, which are fertile. The florets are encased in an involucre of bracts, known as phyllaries. The seeds, known as achenes, often have a tuft of hair, called pappus, which aids in wind dispersal.

Classification

The family Asteraceae is divided into several subfamilies, including Asteroideae, the largest subfamily, which contains many of the well-known genera such as Aster, Chrysanthemum, and Taraxacum (dandelions). Other important subfamilies include Cichorioideae, known for genera like Lactuca (lettuces) and Cichorium (chicories and endives).

Economic Importance

Asteraceae has significant economic importance. Many species are cultivated as ornamentals, including Aster, Dahlia, and Chrysanthemum. Others, such as Helianthus annuus (sunflower), Cynara cardunculus (artichoke), and Lactuca sativa (lettuce), are important food crops. Additionally, some members of the family are used in herbal medicine, such as Echinacea and Artemisia annua (sweet wormwood).

Ecological Role

Members of the Asteraceae family play a crucial role in ecosystems. They provide a vital source of nectar for pollinators, including bees, butterflies, and other insects. Furthermore, the seeds of many Asteraceae species are a food source for birds and small mammals.

Conservation

While many Asteraceae species are common and widespread, some are threatened or endangered due to habitat loss, pollution, and overharvesting. Conservation efforts are essential to protect these species and their habitats to maintain biodiversity.