Essays - by Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321;;


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:

APIACEAECarrot 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.

ASTERACEAESunflower 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.

    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

    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

CAPRIFOLIACEAEHoneysuckle Family
    Shrubs; opposite leaves, no stipules, ovary inferior, syncarpous, 2-8 carpels, fruit a berry (or drupe).  Honeysuckle, viburnum, elderberry, bush honeysuckle

    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

    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

    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

FABACEAELegume 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)

  • Grasses - Stems hollow with 2-ranked leaves, leaves sheathing, ligule at junction of sheath and blade; perianth absent, reduced to lodicules; flower surrounded by bracts (lemma and palea) called a floret; florets subtended by bracts (glumes) comprise a spikelet; the inflorescence described by arrangement of spikelets;  fruit a grain (caryopsis)
  • Sedges � stem solid, not jointed, often triangular, leaves 3-ranked, sheath closed, fruit an achene.  Carex, Scirpus, Cyperus
  • Rushes � Stem solid, not jointed, round, no ligule, perianth of 6 tepals, stigmas 3, fruit a capsule

    Herbs, equitant leaves; petaloid perianth, hypanthium often present; stamens three; inflorescence subtended by a bracts, ovary inferior, tricarpellate, syncarpous.  Iris, blue-eyed grass

    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

    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

MALVACEAEMallow 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

ONAGRACEAEEvening Primrose Family
    Herbs; 4-merous; hypanthium; flowers often yellow; gynoecium syncarpous, four carpels, four stigmas; pollen with plugs, viscin threads; ovary inferior.  Evening primroses

    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. 

    Herbs; leaves compound or dissected, often with sheathing base, no stipules; stamens numerous; carpels numerous, apocarpous.  Buttercups, wild columbine, hepatica, meadow rue, delphinium.

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,

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

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



 © Copyright 12/19/2006 by SG Saupe