Acanthaceae (Acanthus) -- Herbs or shrubs with seeds borne on a characteristic hooked projection.

Brazilian Plume Jacobinia carnea

The flowers are often bilaterally symmetrical, with showy bracts. The corolla has four or five united petals, usually with two-lobed upper lip and three-lobed lower lip; four or five sepals, and two to four stamens. All these parts are attached at the base of the ovary. The leaves are simple (consisting of one whole part), opposite on the stem, smooth margins, with pale streaks or bumps. The fruit is a two-celled capsule. Throughout the world there are about 250 genera and about 2,600 species mostly native to temperate and tropical regions.

Many members of this family are cultivated as ornamental garden plants.

Aceraceae (Maple) -- The family is made up entirely of trees and shrubs. The sap is sweet or milky.

Florida Maple Acer barbatum

The flowers are commonly male and female on separate trees (but may be bisexual) The flowers are often presented in branched clusters; small, with four or five separated sepals. The corolla has four or five over-lapping petals. Stamens number four to ten and arise from the edge of a dark disk. There will be one pistil with a two-celled, two-lobed ovary and two forked styles. The leaves are opposite on the stem, long-stalked, mostly simple in form, broad and palmately lobed, toothed and veined. The leaves are sometimes palmately compound without stipules. Fruit is flat, long winged one-seeded key (samaras).

There are about 125 species, nearly all in the Maple genus. Most are found in temperate regions and south into the tropical mountains. there are 13 known native tree species in North America.

Agavaceae [= Amaryllidaceae] (Yucca or Century Plant) -- The plants are usually perennial. The stems are subterranean or above-ground, often branched, small to gigantic in size.

Spanish Bayonet Yucca aloifolia

The leaves are simple, long-lived, in basal rosettes or at the tip of a woody stem. Some small leaves may protrude directly from the stem. Most leaves are thick and rigid, often with needle-like points. The leaf blades are linear, lance-like, ovate, or elliptic, fibrous, thin and flexible. The leaf margins are entire and often serrate. The flowers are a spike at the end of a tall stem. Each flower is bisexual or unisexual in nature. The perianth is made up of 2 similar petal-like whorls that overlap into a plump tube. The numerous stamens may be hidden or exposed, the filaments are broadened and succulent. The ovary may be superior or inferior.

Fruits are usually capsular and may be winged or lobed; many seeds. Worldwide there are about 17 genera and some 550 species. The plants are commonly found in arid, semitropical or tropical regions. Many genera are used in folk medicine, and the plants provide a number of commercial uses.

Alismataceae (Water Plantain) -- Aquatic or marsh herbs with long-stalked, simple basal leaves and a leafless stalk that bears whorls of small flowers in a much-branched inflorescence or raceme.

Arrowhead Sagittaria latifolia

The flowers are radially symmetrical; three green sepals, three delicate white or pinkish petals, six stamens, six to many separate pistils. The leaves are prominently veined, with bases sheathing the stem. The fruit is one-seeded and hard. The family includes about 15 genera and nearly 100 species, widely distributed in shallow freshwater or muddy habitats in warm and temperate climates.

Amaranthaceae (Amaranth) -- Mostly herbs with inconspicuous flowers, usually in spike-like or head-like clusters, often with brightly colored bracts.

Alligator Weed Alternanthera philoxeroides

The flowers are radially symmetrical, unisexual or bisexual in nature. The calyx has two to five sepals that are often scaly and brightly colored. Petals are absent. Each flowers has five or fewer stamens. All parts of the flower are attached at the base of the ovary. The leaves are simple (consisting of one whole part), and may be opposite or alternate on the stem. Fruit is one-seeded. The family includes about 60 genera and some 900 species.

Most members of this family are abundant in warm climates; some are cultivated as ornamental garden plants. Many are allergy-causing weeds.

Amaryllidaceae (Amaryllis) -- Herbs or (rarely) woody plants, growing from bulbs or underground stems, with narrow basal leaves and a long, leafless flowering stalk.

Jonquil Amaryllis Narcissus jonquilla

The flowers are radially symmetrical, with five sepals and three petals of uniform color and united below into a tube, often with additional parts in the center forming a crown; six stamens. All parts are attached above the ovary. The leaves are grass-like or rigid blades, sharply pointed and with teeth along the margins. Fruit is a berry or capsule. Members of this family are mostly native or tropical and warm regions. There are about 85 known genera and 1,300 species.

Daffodils, Jonquils and Amaryllis are highly prized ornamental garden plants.

Anacardiaceae (Cashew or Sumac) -- Shrubs or small trees with resinous or milky juice.

Winged Sumac Rhus copallina

The flowers are small, bisexual in nature and radially symmetrical in form; usually has five sepals, five petals and five or 10 stamens. All these parts are attached at the base of the ovary. The leaves are alternate on the stem, simple (consisting of one whole part) or pinnately compound (arranged along a central stalk like a feather). Fruit is berry-like. Some species are grown as a garden ornamental for landscape decoration, and some for their edible fruits. Others, such as Poison Ivy, contain a volatile oil that can cause severe skin irritation.

The family consists of about 60 genera and some 400 species, mostly in the tropics but also in temperate regions.

Annonaceae (Custard Apple) -- The Annonaceae are small to medium-sized woody trees, shrubs and vines comprising about 130 genera and some 2,300 species.

Dwarf Pawpaw Asimina parviflora

The flowers are generally solitary on the stem, bisexual in nature and symmetrical in form. Each flower has three sepals and six petals in two series of unequal size. The elongated flower bears many stamens and several to many pistils (male parts). The stamens are short, generally crowded, and consists of a fertile central anther. The pistils have a superior ovary. The leaves are simple (consisting of one whole part), alternately arranged on the stem, no stipules (an appendage at the base of the leaf stalk or leaf), and are generally arranged in flat sprays. Fruit is berry-like, follicles, or aggregate, and often edible.

Apiaceae (Carrot or Parsley) -- Usually aromatic herbs with hollow stems and fern-like leaves.

Angelica Angelica dentata

The flowers are small, borne in umbels, further grouped into a compound unbel. Each flower is radially symmetrical in form, with those near the edge of the compound unbel sometimes bilaterally symmetrical; five small sepals, five petals and five stamens. All these parts are attached at the top of the ovary. The leaves are alternate on the stem, pinnately compound. The fruit splits into two halves, each is 1-seeded. About 300 genera and 3,000 species are found mostly in the Northern Hemisphere. Nearly a quarter of the genera are native to the United States, with several large genera in the West.

The family is important for such foods as carrots, parsnips, and celery and spices and seasonings such as coriander, caraway, anise, parsley, and dill. Some native species are very poisonous.

Apocynaceae (Dogbane) -- Herbs or shrubs (trees in tropical regions) with solitary or clustered flowers and milky juice.

Blue Star, Amsonia tabernaemontana

The flowers are radially symmetrical in form and bisexual in nature. The calyx has five united sepals and the corolla has five united petals. The corolla lobes are often twisted in the bud; five stamens. All these parts are attached at the base of the ovary. The leaves are simple (consisting of one whole part), opposite, whorled, or alternate on the stem. Fruit is 2 pods, often attached at the tip by the style. There are about 200 genera and some 2,000 species, most abundant in the tropics and subtropics. Among them, Oleander and Periwinkle are popular ornamentals.

Other species produce valuable fruits, many are poisonous.

Aquifoliaceae (Holly) -- Mostly evergreen trees or shrubs with toothed leaves and small flowers that are borne solitary or clustered.

American Holly Ilex opaca

Each flower has three to six sepals, four to five petals, and four to five stamens. All parts are attached at the base of the ovary. Male and female flowers are borne on separate plants. The leaves are simple (consisting of one whole part), alternate on the stem, thick and leathery. There are three genera and some 300 species, widely distributed. With their bright red fruits the hollies are important plants for landscape decorations.

Araceae (Arum) -- Members of this family are erect, prostrate, or climbing herbs with numerous small flowers crowded on a fleshy spike (spadix), surrounded by a showy bract (spathe).

Golden Club Orontium aquaticum

The flowers are bisexual or unisexual in nature. The sepals and petals are absent or represented by four to six segments. There will be four to six stamens. All parts of the flower are attached at the base of the ovary. The leaves consist of one whole part or may be compound; long leaf stalks. Fruit is a berry. More than 115 genera and about 2,000 species are found in shady, damp or wet places, most numerous and varied in the tropics.

Many, such as the Calla Lily and Philodendron are cultivated as ornamental plants.

Arecaceae (Palm) -- This family consists of woody shrubs, vines, or trees comprising about 200 genera and 3,000 species that are characterized by having large or very large leaves.

Saw Palmetto Serenoa repens

The leaf has a tubular sheathing base that splits open on one side at maturity. The leaves are alternate on the stem, stalked, and palmately or pinnate to once or twice compound. The flowers are small and clustered in a panicle and are typically subtended by one or more bracts or spathes that may become woody at maturity. Each flower is bisexual in nature, but may also be unisexual. The perianth consists of two whorls of 3 distinct segments each that are distinguished primarily by size, the outer calyx being the smaller. There are six stamens in two whorls of three each, but sometimes there may be several hundred scale-like segments. The pistils have a superior ovary.

The fruit is usually a drupe.

Araliaceae (Ginseng) -- Plants of this family may be trees, shrubs, vines, or herbs with occasionally simple but compound leaves.

Hercules' Club Aralia spinosa

The flowers are small and borne in umbels or head-like clusters. The flowers are radially symmetrical in form, and bisexual or unisexual in nature. The calyx is absent or reduced to four or five points, usually five petals and five stamens. All these parts are attached at the top of the ovary. The leaves are alternate or whorled on the stem, generally pinnately or palmately compound, with three to five leaflets each. Fruit is a berry or berry-like stone.

There are more than 50 genera and about 500 species, found throughout the world in both temperate and tropical regions. Some members, such as English Ivy, are cultivated as flower garden plants or are important drug or flavoring sources.

Aristolochiaceae (Birthwort) -- The plants are herbs or woody vines with commonly heart-shaped leaves and medium-to-large, bizarre, often carrion-scented flowers.

Dutchman's Pipe Aristolochia tomentosa

The flowers are bilaterally or radially symmetrical in form. The calyx is five-lobed or bent with united red, purple, or brown sepals. There are no petals. Each flower has six or more stamens. All these parts are attached to the top of the ovary. The leaves are alternate, stalked or basal and have no teeth along the margins. Fruit is a capsule with 4 to 6 chambers. This is a small family of about six genera and 400 species. The plant members are widely distributed in tropical and temperate regions. Some plants are aromatic; a few are cultivated.

Asclepiadaceae (Milkweed) -- The family consists of herbs or vines usually with thick milky juice.

White-flower Milkweed Asclepias variegata

The flowers are umbel-like clusters (cymes), and tufted seeds are in pods. Each flower is radially symmetrical in form and are borne in flat or round clusters; five sepals. The corolla has five5 united petals with reflexed lobes and a five-lobed crown nestled between the corolla and the stamens. There are five stamens. All parts are attached at the base of the two ovaries. The leaves are simple (consisting of one whole part), mostly paired or in whorls of four, positioned opposite on the stem. Fruit is two pods often joined at the tips by a style filled with many silky-haired seeds.

There are about 250 genera and 2,000 species, widely distributed but most abundant in tropical and subtropical regions.

Asteraceae (Composite Sunflower) -- This family is mainly herbs, but are sometimes found as shrubs or vines, rarely trees.

Black-Eyed Susan Rudbeckia hirta

The flowers are small, but organized into larger heads resembling a single, radially symmetrical flower cupped by a ring of green bracts. The flower-like heads are tiny, forming the disk; larger flowers form around the edge. The rays (resembling petals) are strap-shaped. All flowers in one head may be disk flowers or rays. The flower calyx is absent, or modified into hairs; bristles, scales, or a crown, which often persists atop the fruits. The corolla has five united petals and five stamens. All these parts are attached to the top of the ovary. The leaves are simple or compound, opposite, alternate or whorled along the stem.

Fruit is one-seeded with a hard shell (achene).

In this large, worldwide family there are about some 900 genera and 19,000 species. Many are grown as ornamental. Others and lettuce, sunflowers, and artichokes provide food. Safflower oil is obtained from this family.