SC: Asteridae Order: Asterales Family: Asteraceae “Composites, Sunflowers” 1. 22,000 species in...

SC: Asteridae Order: Asterales Family: Asteraceae “Composites, Sunflowers”

1. 22,000 species in 900 genera 2. Flowers (florets) are typically arranged in HEADS. Expanded

Receptacle; florets epigynous; entire Head surrounded by an involucre of bracts – phyllaries; head is support by a flower stalk called the peduncle; inferior

Pappus – bristles or scales (modified calyx) Corolla – coalescence of petals Stamen – 5 coalescent around style Pistil – one; 2 stigma lobes

SC: Asteridae Order: Asterales Family: Asteraceae “Composites, Sunflowers”

Pappus – bristles or scales (modified calyx)

Corolla – coalescence of petals

Stamen – 5 coalescent around style

Pistil – one; 2 stigma lobes

3. Ray Flowers – 3 of the coalesced petals elongate into a ligule.

4. Great variablity! Sterile, pistilate, staminate, perfect….

Tribes Chicory Tribe –

1. Ray flowers only 2. Milky sap

Lactuca “wild lettuce”, Taraxicum “dandelion”, Chicorium “chicory”

Tribes Ragweed Tribe -

Monoecious; staminate and pistillate flowers on same plant

Ambrosia trifida “giant ragweed”, Ambrosia artemisifolia “small ragweed”

Tribes Aster Tribe -

Style branches flattened in middle….

Solidago “goldenrods”, Aster “asters”

Tribes Sunflower Tribe -

1. Both disc and ray flowers

2. Usually a crown of hairs at base of stigma

3. Pappus mostly bristle-like

Helianthus “sunflowers”, Chrysanthemum “ox-eyed daisy”

Tribes Snakeroot Tribe -

1. disc flowers only 2. leaves mostly

opposite

Eupatorium rugosum “white snakeroot”, Liatris “blazing star”, Eupatorium purpureum “Joe Pye weed”, Eupatorium altissimum “tall thoroughwort”

Tribes Ironweed Tribe –

1. Disc flowers only 2. Anthers sagittate 3. Stigma lobes long

and pointed

Veronia “ironweed”

Tribes Thistle Tribe –

Receptacle with a spiny involucre of bracts

Cirsium vulgare “bull thistle”, Carduus nutans “musk thistle”