Campanulaceae
Campanulaceae, the bellflower or harebell family, is a large family of eudicots in the order Asterales (Asterids), comprising about 84 genera and nearly 2,400 species. As broadly defined by APG classifications (sensu lato), it includes the former Lobeliaceae family (now subfamily Lobelioideae). Members are typically herbs (sometimes shrubs) often containing milky latex, usually with alternate simple leaves, flowers typically 5-merous with fused petals, stamens usually free from the corolla, an inferior ovary, and fruit commonly a capsule. The family exhibits striking variation in floral symmetry, from the radially symmetric bell-shaped flowers of Campanuloideae to the strongly bilaterally symmetric flowers of Lobelioideae.
Overview
The Campanulaceae family has a cosmopolitan distribution but is most diverse in temperate regions of the Northern Hemisphere and tropical mountains. The inclusion of the former Lobeliaceae significantly expands the family's morphological diversity, particularly in flower shape and pollination mechanisms. The core subfamily Campanuloideae is characterized by its often blue or purple, radially symmetric, bell-shaped (campanulate) flowers, like the familiar bellflowers (Campanula) and balloon flowers (Platycodon). Subfamily Lobelioideae features strongly zygomorphic (bilaterally symmetric), often 2-lipped flowers, frequently with fused anthers forming a tube around the style and specialized 'plunger' pollen presentation, as seen in lobelias (Lobelia) and related genera.
Milky latex is common throughout the family. Many species store carbohydrates as inulin, a trait shared with other Asterales like Asteraceae. Horticulturally, the family is very important, providing numerous popular garden perennials and annuals valued for their often vibrant blue, purple, red, or white flowers (Campanula, Lobelia, Platycodon, Symphyandra). Some Lobelia species contain piperidine alkaloids (like lobeline) and have been used medicinally or are toxic.
In Oklahoma (current location as of March 27, 2025), native representatives include Venus' Looking Glass (Triodanis perfoliata) with small purple flowers and clasping leaves, several species of Lobelia such as the striking red Cardinal Flower (Lobelia cardinalis) in wet areas and the blue Downy Lobelia (Lobelia puberula) in woods and prairies, and potentially some true Campanula species in certain habitats.
Quick Facts
- Scientific Name: Campanulaceae Juss. (sensu lato)
- Common Name: Bellflower family, Harebell family
- Number of Genera: Approximately 84
- Number of Species: Approximately 2,380
- Distribution: Cosmopolitan, especially temperate and subtropical regions, tropical mountains.
- Evolutionary Group: Eudicots - Asterids (Campanulids)
- Order: Asterales
- Includes: Former Lobeliaceae (as Subfamily Lobelioideae)
Key Characteristics
Growth Form and Habit
Mostly perennial or annual herbs, sometimes biennial. Some genera, particularly within Lobelioideae in tropical mountains, are shrubs or even small pachycaul (thick-stemmed) trees. Plants often contain milky latex.
Leaves
Leaves are usually alternate and spiral (less commonly opposite or whorled), typically simple (rarely lobed), and lack stipules (exstipulate). Leaf margins are often entire, toothed, or crenate. Basal leaves may form a rosette.
Inflorescence
Inflorescence type is variable; flowers can be solitary (terminal or axillary) or arranged in racemes, spikes, panicles, or sometimes dense heads.
Flowers
Flowers are usually bisexual, typically 5-merous (sometimes 3-10), and often showy. They can be actinomorphic (radially symmetric) or strongly zygomorphic (bilaterally symmetric).
- Calyx: Typically 5 sepals fused at the base (synsepalous), with lobes situated on top of the inferior ovary. Calyx lobes are usually persistent in fruit.
- Corolla: Typically 5 petals fused together (sympetalous).
- In Campanuloideae: Corolla usually actinomorphic, commonly bell-shaped (campanulate), tubular, funnelform, or rotate (wheel-shaped).
- In Lobelioideae: Corolla strongly zygomorphic, usually bilabiate (2 upper lobes, 3 lower lobes), and often resupinate (rotated 180°). The corolla tube is frequently split down the upper side.
- Androecium: Stamens usually number 5, alternate with the corolla lobes. A key feature is that the filaments are typically free from the corolla tube or attached only at the very base (unlike many families with fused petals). Filaments are often broadened or hairy at the base. Anthers may be:
- Distinct (free from each other - Campanuloideae).
- Connate (fused together side-by-side into a tube surrounding the style - characteristic of Lobelioideae).
- Gynoecium: Ovary is characteristically inferior (very rarely superior), composed of usually 2, 3, or 5 fused carpels, forming as many locules. Placentation is usually axile, with numerous ovules per locule. A single style is present, typically with as many stigma lobes as carpels. Stigmas often mature after pollen release (protandry), collecting pollen (sometimes via hairs on the style) before becoming receptive.
Campanula flower (Campanuloideae): Actinomorphic, bell-shaped corolla, free stamens, inferior ovary.
Lobelia flower (Lobelioideae): Zygomorphic, bilabiate corolla, connate anther tube around style, inferior ovary.
Fruits and Seeds
The fruit is predominantly a capsule that dehisces (opens) in various ways, often via pores near the apex (below the persistent calyx), by lateral slits, or apical valves. Less commonly, the fruit is a berry (Canarina). Seeds are typically numerous and small, with fleshy endosperm.
Chemical Characteristics
Plants often contain milky latex. Carbohydrates are frequently stored as inulin (a polysaccharide common in Asterales). Polyacetylenes are common. Alkaloids, particularly piperidine alkaloids like lobeline (in Lobelia), occur in subfamily Lobelioideae and contribute to toxicity/medicinal properties. Iridoids (common in Gentianales and Lamiales) are generally absent.
Identification Basics
Identifying Campanulaceae involves looking for the combination of often milky latex, alternate simple leaves, sympetalous flowers with stamens mostly free from the corolla tube, an inferior ovary, and capsular fruit.
Primary Identification Features
- Habit: Mostly herbs, sometimes shrubs.
- Milky Latex: Often present in stems and leaves.
- Leaves: Usually alternate, simple, exstipulate.
- Flowers 5-merous (Usually): With sympetalous corolla (fused petals).
- Stamens Free from Corolla Tube: Filaments attached only at very base of corolla or free, alternating with lobes.
- Ovary Inferior (Usually): Positioned below attachment of petals/sepals.
- Fruit a Capsule (Usually): Containing numerous small seeds.
Key Subfamily Distinctions
- Campanuloideae: Flowers actinomorphic (bell/rotate); anthers distinct
- Lobelioideae: Flowers zygomorphic (bilabiate, resupinate); anthers connate (fused tube)
Seasonal Identification Tips
- Flowering Season: Mostly spring through summer and fall, depending on species.
- Fruits: Capsules often persist after flowering, sometimes showing characteristic pores or valves for dehiscence below the persistent calyx lobes.
- Vegetative: Alternate simple leaves and milky latex (if present) visible during growing season. Basal rosettes may persist longer.
- (Oklahoma Context: Triodanis flowers spring/early summer. Lobelia cardinalis flowers mid-late summer in wet areas. L. siphilitica and L. puberula flower late summer/fall).
Common Confusion Points
- Asteraceae (Composite Family): Also Asterales, often milky latex, inferior ovary, sympetalous corolla. Key differences: Flowers highly modified into tiny florets aggregated into a composite head (capitulum) surrounded by involucral bracts; stamens fused by anthers around style (syngenesious); fruit a cypsela (achene-like from inferior ovary).
- Gentianaceae (Gentian Family): Often blue/purple sympetalous flowers. Key differences: Ovary superior; leaves usually opposite; stamens attached higher on corolla tube; lack milky latex.
- Boraginaceae (Borage Family): Often blue/purple sympetalous flowers. Key differences: Ovary superior, usually 4-lobed; fruit 4 nutlets; leaves usually alternate and hairy.
- Solanaceae (Nightshade Family): Sympetalous flowers, alternate leaves. Key differences: Ovary superior; fruit often a berry or capsule but different structure; stamens attached to corolla tube; lack milky latex.
- Other families in Lamiales: Often have zygomorphic/bilabiate flowers and superior ovaries (Lamiaceae, Plantaginaceae, Orobanchaceae).
Key combination for Campanulaceae: Milky Latex (often) + Alternate Simple Leaves + Sympetalous Corolla + Stamens Free from Tube + Inferior Ovary + Capsule Fruit. Check flower symmetry and anther fusion for subfamily.
Field Guide Quick Reference (Campanulaceae s.l.)
Look For:
- Herbaceous (mostly), often milky latex
- Leaves alternate, simple (usually)
- Flowers 5-merous, sympetalous
- Stamens 5, free from corolla tube (or base)
- Ovary Inferior (usually)
- Fruit a capsule (usually)
Key Subfamily Clues:
- Campanuloideae: Flowers actinomorphic (bell/rotate); anthers distinct
- Lobelioideae: Flowers zygomorphic (bilabiate, resupinate); anthers connate (fused tube)
Representative Genera and Species
The Bellflower family includes popular garden ornamentals and distinctive wildflowers.
Campanula rotundifolia
Harebell / Bluebell Bellflower
A delicate perennial herb found across temperate Northern Hemisphere, often in grasslands or rocky places. Features a basal rosette of rounded leaves (often withered at flowering) and slender stems with linear leaves bearing nodding, bell-shaped, blue-violet flowers. Represents Campanuloideae.
Lobelia cardinalis
Cardinal Flower
A striking perennial herb native to the Americas, including Oklahoma, found in wet habitats like stream banks and swamps. Produces tall spikes of brilliant red, intensely zygomorphic, bilabiate flowers adapted for hummingbird pollination. Anthers are fused into a tube. Represents Lobelioideae.
Platycodon grandiflorus
Balloon Flower
A perennial herb native to East Asia, popular in gardens. Named for its large flower buds that inflate like balloons before opening into wide, bell-shaped, typically blue-purple (also white/pink), actinomorphic flowers. Represents Campanuloideae.
Lobelia siphilitica
Great Blue Lobelia
A perennial herb native to eastern and central North America (incl. eastern OK), typically in moist woods and meadows. Produces spikes of bright blue, zygomorphic, bilabiate flowers, larger than many other blue lobelias. Anthers fused. Represents Lobelioideae.
Triodanis perfoliata
Venus' Looking Glass / Clasping Bellflower
An annual herb native to North and South America, common in disturbed areas, fields, and open woods in Oklahoma. Stems erect, often unbranched. Leaves alternate, rounded, strongly clasping the stem (perfoliate). Produces small, purple, rotate or shallowly bell-shaped flowers sessile in the leaf axils. Represents Campanuloideae.
Phylogeny and Classification
Campanulaceae is a core family within the order Asterales, belonging to the Campanulid clade of Asterids. This order is characterized by features such as storing carbohydrates as inulin, often having inferior ovaries, and frequent occurrence of secondary pollen presentation mechanisms. Molecular phylogenetics strongly supports the inclusion of the former family Lobeliaceae within Campanulaceae, typically as the subfamily Lobelioideae. This subfamily forms a distinct clade characterized by zygomorphic flowers and connate anthers with plunger pollination.
Within Asterales, Campanulaceae sensu lato is often considered sister to a clade containing Roussaeaceae plus the large Asteraceae (sunflower family) and its close relatives Calyceraceae and Goodeniaceae. The relationships highlight the evolutionary radiation within Asterales leading towards increasingly complex inflorescences (like the Asteraceae head) and specialized pollination mechanisms. The evolution of the bell-shaped flower in Campanuloideae and the highly specialized bilabiate flower with plunger pollination in Lobelioideae represent major divergent paths within the family.
Position in Plant Phylogeny
- Kingdom: Plantae
- Clade: Angiosperms (Flowering plants)
- Clade: Eudicots
- Clade: Asterids
- Clade: Campanulids
- Order: Asterales
- Family: Campanulaceae (incl. Lobelioideae)
Evolutionary Significance
Campanulaceae showcases significant floral diversification within the advanced Asterid order Asterales. The evolution from likely actinomorphic ancestors led to the characteristic bell-shaped flowers adapted for bee pollination in Campanuloideae, and the highly specialized, often resupinate, bilabiate flowers with fused anthers and plunger pollen presentation adapted for birds (e.g., red Lobelia) or specific insects in Lobelioideae. This parallel evolution of complex pollination mechanisms within Asterales (compare Asteraceae's head and Campanulaceae/Lobelioideae's plunger) highlights the selective pressures driving reproductive specialization in derived angiosperm lineages. The common presence of milky latex and inulin storage are also characteristic traits shared across much of the order.
