Flower Forms

In some plants, such as the tulip, each flower grows on its own separate stalk. In many other plants, however, flowers grow in various kinds of clusters. These clusters are called inflorescences. There are two basic kinds of inflorescences: indeterminate and determinate.

Indeterminate Inflorescences

There is no flower at the tip of the flower stalk, which continues to grow and form new flowers along its sides. The oldest flowers are at the bottom. Several kinds of indeterminate inflorescences are shown in the illustration Some Types of Inflorescences (facing page). In head inflorescences, each head appears to be a single flower but is actually many flowers. They are arranged on a horizontal, rather than vertical, axis (stalk). The corollas of the outermost flowers are often enlarged (as in the illustration) to form rays. These rays are commonly (but incorrectly) called petals.

Determinate Inflorescences

The tip of the stalk bears a flower, and other flowers develop, at a later time, below it. The cyme inflorescence shown in the illustration is typical of determinate inflorescence, which is less common than indeterminate.

Representative families of flowers
Subclass Dicotyledonae
Balsam family (Balsaminaceae)
About 450 species of annual or perennial herbs. The flowers are bilaterally symmetrical and have 3 to 5 sepals, 5 petals, and 5 stamens. One of the sepals forms a long, spur-shaped nectary at the back of the flower. Garden balsams, touch-me-nots.
Begonia family (Begoniaceae)
About 900 species. Mostly perennial herbs and shrubs, with staminate and pistillate flowers on the same plant. The staminate flowers have 2 petallike sepals, 2 petals, and many stamens. The pistillate flowers have 2 or more petallike structures called tepals and a compound pistil. Begonias.
Bellflower family (Campanulaceae)
About 1,800 species of annual or perennial herbs. The flowers of most species have 5 sepals, 5 petals, and 5 stamens. In most species, the petals are fused along most of their length, forming a bell-shaped corolla. Bellflowers.
Borage family (Boraginaceae)
About 2,000 species. Mostly annual or perennial herbs; some shrubs and small trees. The flowers of most species have 5 sepals fused at the base, 5 petals fused into a tubular shape at the base, and 5 stamens. Forget-me-nots, heliotropes, lungworts.
Cactus family (Cactaceae)
About 2,000 species. Perennial herbs, shrubs, and trees. Most species have numerous petals, petallike sepals, and many stamens. The petals and sepals are fused at the base. Cactuses.
Composite family (Asteraceae or Compositae)
About 20,000 species. Mostly annual, biennial, or perennial herbs and shrubs. The flowers consist of several to many florets arranged on a head. Ageratums, arnicas, asters, black-eyed Susans, blazing stars, bonesets, calendulas, chicories, chrysanthemums, compass plants, coneflowers, cosmos, dahlias, daisies, dandelions, fleabanes, gaillardias, goldenrods, marigolds, sunflowers, thistles, tickseeds, zinnias.
Crowfoot or buttercup family (Ranunculaceae)
About 1,800 species. Mostly annual or perennial herbs. The majority have 5 petals--or 5 showy sepals in place of petals--and many stamens and pistils. Anemones, bugbanes, buttercups, columbines, delphiniums, hepaticas, larkspurs, marsh marigold, peonies.
Evening primrose family (Onagraceae)
About 650 species. Mostly annual or perennial herbs. The majority have 4 sepals, 4 petals, and 4 or 8 stamens. The sepals are fused, in many cases forming a long tube at the base of the flower. Evening primroses, fireweeds, fuchsias, godetias.
Figwort or snapdragon family (Scrophulariaceae)
About 3,000 species. Mostly annual, biennial, or perennial herbs. Most species have 4 or 5 fused sepals, 4 or 5 petals fused at the base, and 4 stamens. Beardtongues, foxgloves, Indian paintbrushes, monkey flowers, mulleins, slipperworts, snapdragons, toadflaxes.
Gentian family (Gentianaceae)
About 800 species of annual, biennial, or perennial herbs. Most species have 4 or 5 sepals, 4 or 5 petals, and as many stamens as petals. The sepals are fused at the base, forming a cup-shaped calyx. The petals are fused into a tubular shape. Gentians.
Geranium family (Geraniaceae)
About 750 species of annual, biennial, or perennial herbs. Most species have 5 sepals, 5 petals, and 5 or 10 stamens. Crane's-bills, geraniums, pelargoniums, stork's-bills.
Mallow family (Malvaceae)
About 1,500 species. Annual, biennial, or perennial herbs; some shrubs and trees. The flowers have 5 sepals, 5 petals, and many stamens. The filaments of the stamens are fused, forming a tube around the pistil. Hibiscuses, hollyhocks, mallows, rose of Sharon.
Morning-glory family (Convolvulaceae)
About 1,800 species. Mostly annual or perennial herbaceous vines. The flowers have 5 sepals, 5 petals, and 5 stamens. In most species, the petals are fused into a bell- or funnel-shaped corolla. Bindweeds, dodders, moonflowers, morning-glories.
Mustard or cabbage family (Brassicaceae of Cruciferae)
About 3,000 species. Annual, biennial, or perennial herbs. The flowers have 4 sepals and 4 petals in the shape of a cross. Most species have 6 stamens. Candytuft, cresses, mustards, rockets, stocks, sweet alyssum, wallflowers.
Nasturtium family (Tropaeolaceae)
About 50 species of annual or perennial herbs. The flowers of most species have 5 sepals, 5 petals, and 8 stamens. One or more of the sepals form a spur at the back of the flower. Canary creeper, nasturtiums.
Nightshade family (Solanaceae)
About 2,200 species. Mostly annual or perennial herbs; some shrubs and trees. The flowers have 5 fused sepals, 5 petals fused into the shape of a star or funnel; and 5 stamens. Belladonna, flowering tobacco, ground cherries, henbane, jimsonweed, petunias.
Parsley or carrot family (Apiaceae or Umbelliferae)
About 2,900 species. Mostly biennial or perennial herbs. In most species, the flowers are small and arranged in umbrella-shaped clusters. The florets have 5 sepals, 5 petals, and 5 stamens. Queen Anne's lace, rattlesnake masters, sweet cicely, water pennyworts.
Pea family (Fabaceae or Leguminosae)
About 17,000 species. Annual or perennial herbs; many shrubs and trees. The flowers of most species have 5 fused sepals, 5 petals, and 10 or many more stamens. Acacias, brooms, clovers, locoweeds, lupines, mimosas, redbuds, sweet pea, wild indigos, wisterias.
Phlox family (Polemoniaceae)
About 300 species. Mostly annual or perennial herbs. The flowers have 5 fused sepals, 5 petals, and 5 stamens. The petals are fused at the base. Phloxes, polemoniums.
Pink family (Caryophyllaceae)
About 2,100 species. Mostly annual, biennial, or perennial herbs. The flowers of most species have 5 sepals, 5 petals, and 5 or 10 stamens. Baby's-breath, campions, carnations, pinks, sweet Williams.
Poppy family (Papaveraceae)
About 250 species. Mostly annual or perennial herbs. The majority have 4 petals, 2 or 3 sepals, and many stamens. Bloodroot, poppies.
Primrose family (Primulaceae)
About 800 species of annual or perennial herbs. Most species have 5 sepals, 5 petals, and 5 stamens. The petals are fused into a tubular shape at the base. The sepals are fused into a cuplike shape. Cyclamens, loosestrifes, pimpernels, primroses.
Rose family (Rosaceae)
About 3,200 species of perennial herbs, shrubs, and trees. The flowers of most species have 5 sepals, 5 petals, and numerous stamens. Agrimonies, cherry laurel, cinquefoils, cotoneasters, hawthorns, mountain avens, pyracanthas, roses, spiraeas.
Saxifrage family (Saxifragaceae)
About 1,200 species. Mostly perennial herbs and shrubs; some small trees. The flowers of most species have 5 sepals, 5 petals, and 5 or 10 stamens. Coralbells, deutzias, hydrangeas, mock oranges, saxifrages.
Violet family (Violaceae)
About 850 species. Mostly perennial herbs and shrubs. The flowers have 5 sepals, 5 petals, and 5 stamens. In many species, the petal nearest the stem is larger than the others and has a hollow sac or spur at the back. Pansies, violas, violets.
Subclass Monocotyledonae
Amaryllis family (Amaryllidaceae)
About 1,300 species. Mostly perennial herbs. The flowers have 6 tepals and 6 stamens. All the floral parts, including the pistil, are fused at the base of the flower. Amaryllises, daffodils, jonquils, narcissuses, snowdrops.
Iris family (Iridaceae)
About 1,500 species of perennial herbs. The flowers have 3 petallike sepals, 3 petals, and 3 stamens. All the floral parts are fused at the base, forming a tube. Crocuses, freesias, gladioli, irises.
Lily family (Liliaceae)
About 650 species. Mostly perennial herbs. The flowers of most species have 6 tepals and 6 stamens. In some species, the tepals are fused at the base. Dogtooth violets, fritillaries, lilies, tulips.
Orchid family (Orchidaceae)
More than 20,000 species of perennial herbs with bilaterally symmetrical flowers. The flowers of most species have 3 petallike sepals; 3 petals; and 1 or 2 stamens, which are fused with the style. Fairy-slippers, lady's-slippers, orchids, pogonias.