Plant Families for Gardeners
(prepared for a presentation at the Minnesota Master Gardener Conference, Summer 2004)
Plant Families – What and Why?
The family is the basic unit of classification used by taxonomists. A family consists of a group of related genera that share a characteristic set of features. Learning family characteristics is useful because: (a) family naming/taxonomy is relatively stable; (b) it applies to any flora; (c) there are a manageable number to learn; about 400 for flowering plants vs. 250,000 species); (d) an unknown species is relatively easy to identify once its family is known. According the International Code of Botanical Nomenclature, family names end in “-aceae.”
20 Common Plant Families:
APIACEAE – Carrot Family
Herbs, hollow and furrowed stems, leaves compound or dissected with sheathing leaf base; flowers 5-merous, often white or yellow; inflorescence an umbel (compound); style swollen over ovary (stylopodium); ovary inferior, fruit a schizocarp. Carrots, celery, dill, parsley
APOCYNACEAE (or ASCLEPIADACEAE)
– Dogbane or Milkweed Family
Herbs and shrubs, leaves opposite or whorled, milky sap; flowers 5-merous; many with a corona (with a hood and horn); anthers fused to gynoecium (gynostegium); pollen in pollinia connected by two arms (translators) to a central body (corpusculum); gynoecium bicarpellate, fused at apex; fruit a follicle, seeds comose. VInca, milkweed.
– Sunflower Family
Herbs (our species) with flowers inserted on a receptacle surrounded by bracts (head inflorescence); flowers may be regular (disk) or irregular (ray or ligulate); calyx reduced to pappus; stamens 5, anthers connate; ovary inferior, fruit an achene. Many species.
– Borage Family
Herbs, often hairy or bristly; leaves alternate, stem round; ovary bicarpellate, 4-lobed, style gynobasic; fruit of 4 nutlets, inflorescence cymose (scorpiod or helicoid). Bluebells, comfrey, forget-me-nots
– Mustard Family
Herbs, acrid taste (glucosinolates); flowers 4-merous; petals cruciform, often clawed; stamens tetradynamous (4 long, 2 short); fruit with a false septum, siliques and silicles. Horseradish, broccoli, cabbage
– Honeysuckle Family
Shrubs; opposite leaves, no stipules, ovary inferior, syncarpous, 2-8 carpels, fruit a berry (or drupe). Honeysuckle, viburnum, elderberry, bush honeysuckle
– Pink Family
Herbs, swollen nodes, opposite leaves joined by a transverse line, flowers 5-merous, petals notched at end; gynoecium 2-5 carpels, free central placentation; fruit a capsule, opening by teeth or valves. Carnations, pinks
– Gourd Family
Vines, prostrate or climbing; leaves palmately-lobed or compound, tendrils; stems often 5-angled, bicollateral vascular bundles; flowers imperfect, often yellow or white; stamens highly modified, usually 5, connate; gynoecium 3-carpelled, syncarpous; placentation parietal; fruit a berry or pepo; rich in bitter tasting tetracyclic triterpenoids and alkaloids. Pumpkins, melons, gourds
– Spurge Family
Herbs (ours); milky sap; flowers highly reduced; staminate flowers a single stamen; pistillate flowers a single pistil, tricarpellate, syncarpous; flowers borne in cup-like structure (cyathium) often with glands on margin; colorful bracts may subtend inflorescence; fruit a schizocarpic capsule. Snow-on-the-mountain
– Legume or Bean Family
There are three distinctive groups or subfamilies of legumes. The only common one in Minnesota is the Papillionoideae and is described here: Herbs, shrubs or trees, flowers zygomorphic; corolla papilionaceous (uppermost banner, two lateral wings, two fused keel petals); unicarpellate; fruit a legume. Many species.
GRASS-LIKE PLANTS (Poaceae – Grasses; Cyperaceae – Sedges; Juncaceae – Rushes)
– Iris Family
Herbs, equitant leaves; petaloid perianth, hypanthium often present; stamens three; inflorescence subtended by a bracts, ovary inferior, tricarpellate, syncarpous. Iris, blue-eyed grass
– Mint Family
Herbs and shrubs, square stems, often aromatic; leaves opposite; flowers 5-merous, irregular, bilabiate; stamens 2 or 4, epipetalous, ovary 4-lobed, style gynobasic, fruit 4 nutlets. Rosemary, sage, thyme
– Lily Family
Although this family is now broken up into smaller ones, the following is a good unifying description: Herbs, perennial from bulbs, corms rhizome or tubers; leaves linear with parallel veination; flowers regular; perianth 3-merous, 6 tepals; gynoecium tricarpellate, syncarpous, ovary superior. Lilies, tulips
– Mallow or Cotton Family
Herbs, often with mucilaginous sap; leaves stipulate, palmately veined and lobed; epicalyx often present; corolla 5 petals; stamens numerous, monadelphous, epipetalous; fruit a capsule, seeds comose. Hollyhocks
– Evening Primrose Family
Herbs; 4-merous; hypanthium; flowers often yellow; gynoecium syncarpous, four carpels, four stigmas; pollen with plugs, viscin threads; ovary inferior. Evening primroses
– Orchid Family
Herbs, perennial, leaves often coriaceous and two-ranked; flowers highly irregular, 3-merous; lower petal modified into a lip (labellum), twists 180 degrees during development; pollen aggregated into a waxy mass (pollinia); androecium and gynoecium fused into a column; ovary inferior, numerous tiny seeds.
– Buttercup Family
Herbs; leaves compound or dissected, often with sheathing base, no stipules; stamens numerous; carpels numerous, apocarpous. Buttercups, wild columbine, hepatica, meadow rue, delphinium.
– Rose Family
Herbs, shrubs or trees; leaves stipulate, often serrate, flowers 5-merous; hypanthium, stamens numerous, fruits variable (achenes, follicles, drupes, pomes). Variable family, includes strawberry, stone fruits, apples, spiraea,
– Figwort Family
Herbs (and shrubs); flowers irregular, bilabiate, 5-merous; stamens 4 (or 5), epipetalous, didynamous (2 long, 2 short), a fifth stamen often present as a staminode; gynoecium syncarpous, bicarpellate, ovary 2 locules, placentation axile; ovary superior. Foxglove, penstemon, mullein
– Tomato Family
Herbs, alternate leaves; bicollateral vascular bundles; flowers actinomorphic; calyx 5-merous, often persistent in the fruit; corolla 5-merous, various but may be plicate; androecium 5 stamens, epipetalous; gynoecium bicarpellate, syncarpous; fruit a berry or capsule; rich in alkaloids. Eggplant, tomato, potato, pepper