Wild Morning Glory

Wild morning glory (Calystegia macrostegia) is a native vine that twists its stems around and among the plants of the coastal sage scrub and chaparral, or twines itself together into a flower sprinkled carpet. The bright green arrow-shaped leaves and showy white trumpet-shaped flowers decorate the most nondescript vegetation.

Wild morning glory is native only to the Channel Islands, coastal southern California and Baja California.

Wild morning glory is often called false-bindweed because of its resemblance to the non-native bindweed, considered one of the worst weeds in California. Flowers of the native species are carried on leafless stems, while the flower stems of the invasive look-alike are shorter and have a pair of small leaves (bracts) midway along the them.

Description ^2,4,59

Wild morning glory is a perennial vine that climbs by coiling around the branches of shrubs; it may also grow without support on the ground, the stems twining around each other. Several vines up to12 feet (3.5 m) long arise from the same deep, woody rootstock. The smooth, green leaves are arrow-shaped, up to five inches (13 cm) long. The vine becomes dormant in summer.

In the bud, the petals are pleated and twisted, unfolding into a flower like the elements of a camera aperture. The calyx consists of five sepals of unequal size; surrounding the calyx are two larger purplish-green bracts. The bisexual flowers are trumpet-shaped, white, sometimes with a pinkish tinge, sometimes with five pinkish-green stripes on the underside. Flowers are up to two inches (5 cm) across on stems one to four inches (2.5 – 10 cm) long.  Five petals are fused into a corolla, which is pleated, corresponding to the pleats in the bud. Five stamens each have a spherical,granular-appearing anther bearing white pollen. A single pistil has one style that is two-lobed near the top, with two stigmas; the stigmas are swollen and clearly differentiated from the style. Major bloom time is March-August.¹

The fruit is a capsule enclosed by papery sepals, which in turn may be enclosed by the bracts. Each capsule has two to four wedge-shaped seeds, which are dark brown and warty.

Classification  

Wild morning glory is a dicot angiosperm in the morning glory family, Convolvulaceae. This is a family centered in warmer regions,⁷¹ distinguished by trumpet-shaped flowers and by characteristics of the reproductive structures.^2,143 Species are often twining vines, and leaves are often arrow-shaped.⁵⁹ The sweet potato is a member of this family, as are species of parasitic dodder, such as California dodder and salt marsh dodder that are found in the Reserve.⁴⁸ The most infamous member of the family is field bindweed, a non-native vine that is a troublesome pest in agricultural areas¹⁴⁴ from where it escapes into wildlands.

Genera are distinguished by the structure of the pistil. Calystegia species have a single style with two oblong stigma lobes.²

There are six subspecies of C. macrostegia in California,⁷ and they are not always easy to tell apart.⁴ The one reported from the Reserve is ssp. tenuifolia,⁴⁸  but all the ones we have examined have the greater width and shape of the leaf blade resembling ssp. intermedia. [note: since writing this, we have learned of a recent study suggesting that both subspecies are environmentally induced variants of ssp. arida.²⁸⁰]

Ecology ¹⁴

Wild morning glory vines often appear in incredible numbers after a fire,³⁵ especially on rocky, south-facing slopes.¹⁷⁴ The species has two strategies for recovering after a wild fire. Seed germination is enhanced by heat, and vines can resprout from the woody rootstock.

Human Uses  

All species in the morning glory family have some degree of purgative properties,⁹² but we have found no specific medicinal uses of our species by native Americans or by modern herbalists.

Wild morning glory is used in native gardens and is especially recommended as a slope cover.⁷⁹

Interesting Facts  

Unlike ornithologists, who insist that only one common name be applied across a bird’s entire range, botanists let common plant names evolve as they may. This may result in a few local names for a species, but doesn’t usually present a problem. However, for the unassuming Calystegia macrostegia, common names have run amok. Names used in the local literature range from the most common and least descriptive name, island false-bindweed, ^7,41,48,67 to island morning glory,^7,83 California morning glory,^79,83 woody morning glory,⁸³ large-bracted morning-glory,⁵⁹ wild morning glory^23,174, and just plain morning glory^1,14,35 ( or morning-glory.⁸ ) The Jepson eFlora shuns the controversy and lists no common name. We have departed from our usual policy of closely following the Jepson eFlora and/or CalFlora and have opted for the more descriptive, but less common, common name: wild morning glory.

The name false-bindweed comes from the resemblance of wild morning glory to the non-native field bindweed (Convolvulus arvennsis), considered one of the most troublesome weeds of agricultural fields in temperate climates worldwide.¹⁴⁴ One way to distinguish the two is by the presence of a pair of small leaf-like bracts on the stem of the bindweed flower; on the stem of wild morning glory, the analogous bracts are immediately below the flower, enclosing the calyx so the stem is bare.¹¹

The Chumash gave wild morning glory the not-so-descriptive but thought-provoking name of s’epsu”i’ashk’a’, which means “Coyote’s basket-hat”.¹⁵