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The Asteraceae is cosmopolitan (worldwide in distribution), found especially in temperate and tropical montane regions and open and/or dry habitats. The family is of some economic importance for food production: Cichorum (endive, chickory), Cynara (artichoke), Helianthus (sunflower seeds and oil, Jerusalem artichoke), Taraxacum (dandelion greens), and Lactuca (lettuce). Spices come from Artemisia (wormwood, tarragon); insecticides come from Tanacetum (pyrethrum) and Pulicaria (fleabane). Ambrosia (ragweed) pollen is a major cause of hayfever. Numerous genera are important as ornamentals: Calendula (marigold), Leucanthemum (chrysanthemum), Dahlia, Tagetes (French marigold), Senecio, Gaillardia (blanket flower), Helianthus (sunflower), Zinnia, and many others.

The Asteraceae in our flora are all perennial or annual herbs. They have alternate, opposite or whorled leaves, usually simple but sometimes deeply lobed or dissected, smooth-margined or toothed, and no stipules. The flowers are densely packed into heads that are surrounded by an involucre. The individual flowers are tiny and highly modified. The sepals are modified into a pappus, or plume, that lets the fruits float away on the wind at maturity. There are 5 petals fused into a tube with all lobes approximately symmetrical in the interior of the head (disk flowers), but asymmetrical with one very large lobe ("petal") at the head margin (ray flowers). Sometimes heads have only disk flowers, or only ray flowers, but usually both are present. Within each flower, there are usually 5 stamens with their anthers fused into a ring. Pollen is released into the center of the ring, and the immature style expands and pushes the pollen out like a plunger. The ovary has 2 carpels and is inferior. There are 2 style branches that can be seen when the stigmas become receptive. The fruits are achenes (containing a single seed), usually dispersed by their feathery pappus.

(Click on a picture to see more about that species)

			circium_arvense.htm
Achillea millefolium	Anaphalis margaritacea	Bellis perennis	Circium arvense
			lapsana_communis.htm
Hieracium albiflorum	Hypochaeris radicata	Lactuca muralis	Lapsana communis
		petasites_palmatus.htm
Leucanthemum vulgare	Matricaria discoidea	Petasites palmatus	Senecio sylvaticus
	tanacetum_vulgare.htm
Senecio vulgaris	Tanacetum vulgare	Taraxacum officianale	Tragopogon dubius