Convolvulaceae
Morning Glory Family / Bindweed Family
Convolvulaceae, the morning glory or bindweed family, comprises about 58 genera and roughly 1,800 species of eudicots in the order Solanales. The family is best known for its numerous twining herbaceous vines, typically bearing alternate leaves (often heart- or arrowhead-shaped) and showy, funnel-shaped flowers with 5 fused petals that are often pleated or twisted in bud. The family also includes shrubs, trees, and the unusual parasitic, leafless vines of the genus Cuscuta (dodders). The fruit is typically a capsule.
Overview
Distributed worldwide but most diverse in tropical and subtropical regions, the Convolvulaceae family includes species ranging from major food crops to beloved ornamentals and troublesome weeds. The most economically important member is the Sweet Potato (Ipomoea batatas), cultivated for its starchy tuberous roots. Many other Ipomoea species are grown as morning glories for their beautiful, often ephemeral flowers that typically open in the morning sun. Moonflowers (Ipomoea alba) have large white flowers that open at night.
However, the family also contains aggressive weeds like Field Bindweed (Convolvulus arvensis) and Hedge Bindweed (Calystegia sepium), which can be problematic in gardens and agriculture due to their persistent rhizomes and twining habit. A particularly unusual lineage within the family is the genus Cuscuta (dodders). These are parasitic plants lacking chlorophyll and significant leaves, appearing as yellow or orange thread-like stems that twine around host plants, extracting nutrients via specialized structures called haustoria. Some members of the family, particularly seeds of certain Ipomoea, contain ergoline alkaloids related to LSD and have been used historically in ritual contexts.
In Oklahoma (current location as of March 2025), common representatives include Field Bindweed (Convolvulus arvensis), native Hedge Bindweed (Calystegia sepium), various native and cultivated morning glories (Ipomoea species), and the non-vining Shaggy Dwarf Morning-Glory (Evolvulus nuttallianus).
Quick Facts
- Scientific Name: Convolvulaceae Juss.
- Common Name: Morning Glory family, Bindweed family
- Number of Genera: Approximately 58
- Number of Species: Approximately 1,800 (incl. Cuscuta)
- Distribution: Cosmopolitan, most diverse in tropical and subtropical regions.
- Evolutionary Group: Eudicots - Asterids (Lamiids)
- Order: Solanales
Key Characteristics
Growth Form and Habit
Predominantly twining or trailing herbaceous vines. Also includes erect herbs, shrubs, and small trees. Milky or clear latex is sometimes present. The genus Cuscuta consists of non-photosynthetic, parasitic vines with highly reduced vegetative structures, attaching to host plants via haustoria.
Leaves
Leaves are usually simple and arranged alternately along the stem (rarely opposite). Leaf shape is often cordate (heart-shaped) or sagittate (arrowhead-shaped), but can also be linear, entire, lobed, or even palmately compound. Venation is typically pinnate or palmate. Stipules are absent. In Cuscuta, leaves are reduced to tiny, non-functional scales or are entirely absent.
Inflorescence
Flowers are often borne solitary in the leaf axils or in few-flowered axillary clusters (cymes). Sometimes flowers are grouped into terminal or axillary heads, panicles, or racemes. Inflorescences are often subtended by bracts.
Flowers
Flowers are typically bisexual, actinomorphic (radially symmetric), usually 5-merous, and often large and showy (except in Cuscuta). Key features include:
- Calyx: Composed of 5 distinct (free) sepals, which are often unequal in size. The sepals are typically persistent in fruit and may sometimes enlarge.
- Corolla: Composed of 5 fused petals (sympetalous) forming a characteristic funnel-shaped (funnelform), bell-shaped (campanulate), or trumpet-shaped structure. A key feature is that the corolla is often plicate (having distinct vertical pleats or folds) and convolute (twisted) in bud, resulting in a star-like pattern or defined mid-petal areas when the flower opens. Colors are diverse (white, blue, purple, pink, red, yellow).
- Androecium: Stamens number 5, alternate with the corolla lobes, and are attached to the base of the corolla tube (epipetalous). Filaments are often unequal in length, and their bases may be hairy. Anthers dehisce via longitudinal slits.
- Gynoecium: Ovary is superior, typically composed of 2 fused carpels (sometimes 3-5). It usually forms 2 locules (or 1, or 3-5), each containing typically 1 or 2 ovules attached near the base (basal-axile placentation). Style(s) are usually terminal, either single and undivided, single and branched, or rarely two distinct styles. Stigmas are variable in shape (capitate, globose, lobed, linear). A nectar disc is usually present around the base of the ovary.
- Cuscuta Flowers: Small, often whitish or yellowish, typically 4- or 5-merous, with scale-like appendages (infrastaminal scales) often present inside the corolla tube below the stamens.
Fruits and Seeds
The fruit is most commonly a dry capsule that dehisces by splitting into valves (valvular), breaking apart irregularly, or sometimes opening via a circumscissile lid. Less often, the fruit is a fleshy berry or a hard, nut-like structure. Seeds are typically few (1-4 per fruit), often have a hard seed coat, and may be smooth or hairy. The embryo is often folded or coiled within the endosperm.
Chemical Characteristics
Many species contain resin glycosides (also called convolvulin glycosides). A significant feature is the presence of ergoline alkaloids (chemically related to LSD) in the seeds of several genera, particularly Ipomoea, Argyreia, and Turbina. Tropane alkaloids, characteristic of the related Solanaceae family, are generally absent. Milky latex occurs in some genera.
Field Identification
Identifying Convolvulaceae often involves recognizing the vining habit, alternate leaves, and characteristic funnel-shaped flowers. The parasitic Cuscuta is unmistakable.
Primary Identification Features
- Twining/Trailing Habit: Most species are vines (herbaceous).
- Alternate, Simple Leaves: Leaves typically alternate, simple, often heart-shaped or arrowhead-shaped (except Cuscuta).
- Funnel-Shaped Corolla: Flowers usually large, with 5 fused petals forming a funnel or trumpet shape, often pleated/twisted in bud.
- 5 Stamens Attached to Corolla: Stamens distinct, attached low inside the corolla tube.
- Superior Ovary: Ovary sits above the attachment of sepals/petals.
- Capsule Fruit: Fruit typically a dry capsule containing few seeds.
- For Cuscuta: Leafless, non-green (yellow/orange) parasitic vine twining on host plants, with small clustered flowers.
Secondary Identification Features
- Milky Latex: Sometimes present when stems/leaves are broken.
- Plicate/Convolute Corolla Bud: Twisted and folded appearance of the flower bud is characteristic.
- Persistent Sepals: Sepals often remain (and may enlarge) around the fruit.
- Leaf Shape Details: Specific shape (cordate, sagittate, linear, lobed) can help distinguish species.
- Flower Color and Size: Aids in species identification.
Seasonal Identification Tips
- Summer/Fall: Peak flowering season for most morning glories and bindweeds. Flowers are best observed in the morning as many close in the afternoon heat.
- Growing Season: Vining stems and characteristic leaves are present.
- Summer/Fall (Cuscuta): Dodder becomes conspicuous as yellow/orange masses covering host vegetation, producing flowers and fruits.
- (Current Time Context: Late March in Oklahoma - Too early for significant flowering of most native or weedy Convolvulaceae. Overwintering roots/rhizomes of perennials like bindweed may be present underground).
Common Confusion Points
- Malvaceae (Mallow family): Some (Hibiscus) have large, showy flowers, but leaves often palmately lobed/veined, stamens fused into a column around the style, fruit often a schizocarp or differently structured capsule.
- Apocynaceae (Dogbane family): Some are vines (Mandevilla), but leaves usually opposite, often milky latex, flower structure differs (often salverform, may have corona), fruit usually paired follicles.
- Bignoniaceae (Trumpet Creeper family): Woody vines (Campsis) with trumpet-shaped flowers, but leaves usually opposite and compound, fruit a long capsule with winged seeds.
- Cucurbitaceae (Gourd family): Herbaceous vines, but climb with tendrils (usually), leaves often palmately lobed, flowers typically unisexual, ovary inferior.
- Polygonaceae (Buckwheat family): Some (Fallopia) are weedy vines, but have papery sheaths (ocrea) at nodes, small flowers usually lacking distinct large petals, fruit an achene.
Key features for Convolvulaceae (excluding Cuscuta): Twining habit + Alternate leaves (often heart/arrowhead) + Funnelform/plicate corolla + 5 stamens + Superior ovary + Capsule fruit.
Field Guide Quick Reference
Look For:
- Twining/trailing herb (mostly)
- Alternate, simple leaves (often cordate/sagittate)
- Funnel-shaped fused corolla (plicate/convolute bud)
- 5 stamens attached to corolla base
- Superior ovary
- Fruit usually a capsule
- (Or: Cuscuta - parasitic yellow/orange vine)
Key Variations:
- Habit (vine, herb, shrub, parasite)
- Leaf shape
- Flower size and color
- Presence of latex
- Sepal characteristics
- Non-vining genera (Evolvulus)
Notable Examples
The Morning Glory family includes major food crops, popular ornamentals, widespread weeds, and unique parasites.
Ipomoea purpurea
Common Morning Glory
An annual twining vine native to Mexico and Central America, widely cultivated and naturalized globally, often considered weedy. Features heart-shaped leaves and large, funnel-shaped flowers typically purple, blue, pink, or white, opening in the morning. Sepals are usually narrow and pointed. Fruit is a capsule.
Convolvulus arvensis
Field Bindweed
A perennial vine native to Eurasia, now a notoriously persistent cosmopolitan weed in agriculture and gardens, common in Oklahoma. Spreads via deep rhizomes and twining stems. Has arrowhead-shaped leaves and smaller, funnel-shaped white or pinkish flowers. Distinguished from Calystegia by lacking large bracts enclosing the calyx.
Calystegia sepium
Hedge Bindweed / False Bindweed
A perennial vine native to temperate regions worldwide, including Oklahoma. Similar in habit to Convolvulus arvensis with arrowhead leaves and twining stems, also spreading by rhizomes. Key difference: flowers are larger (white or pink) and the calyx is enclosed by two large, prominent bracts (bracteoles).
Ipomoea batatas
Sweet Potato
A sprawling perennial vine (usually grown as an annual) of tropical American origin, cultivated globally for its large, starchy, sweet-tasting tuberous roots. Leaves are variable, often heart-shaped or lobed. Flowers are typical funnel-shaped morning glories, pinkish-purple, though flowering can be infrequent in temperate cultivation. A major staple food crop.
Cuscuta species
Dodder
A genus of over 150 species of parasitic plants found worldwide. They lack chlorophyll (appear yellow, orange, or reddish) and significant leaves/roots. Thin, thread-like stems twine around host plants, penetrating them with haustoria to extract water and nutrients. Produce clusters of small, whitish, bell-shaped flowers (often 4- or 5-merous) followed by small capsules.
Evolvulus nuttallianus
Nuttall's Evolvulus / Shaggy Dwarf Morning-Glory
A small, non-vining perennial herb native to central North America, including prairies and open areas in Oklahoma. Forms low clumps with erect or spreading stems covered in dense silky hairs. Leaves are small, narrow, and alternate. Produces small, solitary, funnel-shaped blue or lavender flowers in leaf axils. Represents an non-twining lineage in the family.
Phylogeny and Classification
Convolvulaceae belongs to the order Solanales, within the Lamiid clade of Asterids. Its closest relative within the order is the Solanaceae (Nightshade family), sharing features like fused petals, 5 stamens, and often superior ovaries, although differing significantly in chemistry (e.g., presence/absence of tropane vs. ergoline alkaloids) and fruit types.
The inclusion of the highly modified parasitic genus Cuscuta within Convolvulaceae is strongly supported by molecular data, indicating that parasitism evolved from autotrophic, vining ancestors within the family. The characteristic funnel-shaped, plicate corolla represents a key morphological synapomorphy for much of the family. The family exhibits considerable diversification in habit (from vines to trees) and adaptation to various environments.
Position in Plant Phylogeny
- Kingdom: Plantae
- Clade: Angiosperms (Flowering plants)
- Clade: Eudicots
- Clade: Asterids
- Clade: Lamiids
- Order: Solanales
- Family: Convolvulaceae
Evolutionary Significance
Convolvulaceae exemplifies the successful evolutionary radiation of the twining vine habit among angiosperms. The development of the fused, funnel-shaped corolla, often with intricate folding (plication) and twisting (convolution) in bud, is a hallmark of the family and likely relates to pollination syndromes. The evolution of complete parasitism and drastic morphological reduction in Cuscuta from within a family of photosynthetic plants provides a fascinating case study in evolutionary transitions. The family's economic impact, through both the vital food crop sweet potato and problematic agricultural weeds, underscores its ecological and societal importance.
