Morning glory — friend or foe?

Morning glories have been grown, cultivated, and loved for more than 1,300 years. Countless people have enjoyed their subtle and vibrant colors and their familiar, comforting presence. This easy-to-grow vine is a common sight in many neighborhoods. Unfortunately, this ornamental vine can be an aggressive, fast-spreading weed that invades natural landscapes and threatens food crops, depending on the species and the climate where the plant is growing.

A morning glory is a twining vine with typically heart-shaped leaves, but the leaves can also be three-lobed. Flowers bloom in late spring and can continue into early winter, depending on location. True to their name, these trumpet-shaped flowers open in the early morning and close again by midday or early afternoon. This plant can behave as a perennial or an annual. In mild climates, morning glories grow continuously from the original vine for two years or more as a perennial. In harsher climates, they are annuals, perishing in the tropical dry season or killed by cold temperatures in the north. Annuals rely on their abundant seed distribution to regenerate each year.

Morning glory primarily refers to species within the large flowering plant genus Ipomoea in the family Convolvulaceae. Morning glories grow worldwide, including parts of the Americas, Africa, and Asia.

The commercial varieties sold in stores in the United States are primarily derived from two native species from Mexico, the Ipomoea purpurea (common), which has been cultivated through selective breeding to produce varieties such as Kniola’s black night and crimson rambler. The species Ipomoea tricolor (archetypical) has produced varieties including heavenly blue, flying saucers and pearly gates.

Ipomoea nil is the ivy-leafed or Japanese morning glory, native to tropical America but heavily cultivated in Asia, producing varieties such as Shiryu, or “Purple Dragon,” a distinct historical-to-modern line with deep purple color and elegant structure.

The Edo period, from 1603 to 1867, was a time of intense plant cultivation in Japan, even as the country embraced the philosophy of isolationism. Henka Asagao, or “mutant morning glory,” was loved by Japanese cultivators for its wide array of cultivated varieties with fancy and bizarre phenotypes expressing features like striped or ruffle-edged flowers, and exotic leaf patterns. There is a tradition in Japan of naming the morning glories systematically according to their characteristics.

Ornamental varieties of morning glories are grown commonly in gardens around the world, but they can grow aggressively and are considered noxious weeds in frost-free zones where they continuously grow from their rootstocks, in addition to producing large amounts of annual seeds. Morning glories are listed as a nuisance in southern states. They are restricted by the U.S. Department of Agriculture in states like Arizona, where non-native, highly invasive species outcompete both crops and native vegetation. This is the same for Australia, New Zealand and South Africa where specific varieties are classified as noxious weeds and banned.

In Mexico, Aztec priests and healers incorporated morning glory seeds from the variety Ipomoea corymbosa into their ceremonies. They called the seeds “ololiuhqui” (round thing) and the vine “coaxihuitl” (snake plant). The seeds have an active compound called lysergic acid amide (LSA), which was used as a hallucinogen similar to LSD for healing, diagnosis, and communication with the world beyond.

On my trips to Mexico in late fall, the native morning glories are growing and flowering everywhere. Mexico is a primary global hotspot for the Ipomoea genus. Most of the native varieties have much smaller flowers than those typically seen in U.S. gardens. Mexico is blessed with approximately 180 native species, most of which are recorded on Mexico's National Commission for the Knowledge and Use of Biodiversity platform, CONABIO EncicloVida. Many of these species are endemic to the country and found in its myriad of diverse microclimates, concentrated on the Pacific Coast from the southernmost state of Chiapas to northern Baja California. Common species include the white moonflower, the night-blooming morning glory, and the scarlet morning glory with its small red flower.

Whether wild or intentionally grown in a garden, morning glories have been living alongside humans for a millennium.