You’re growing morning glories? On purpose? Are you crazy? Those things will take over your garden! Our friends, who live in wet western Washington, were appalled. They couldn’t understand why I’d plant something so invasive.
Yet, I’ve grown morning glories for years, first in California’s benign climate, then here in Colorado. I’ve never found them to be at all invasive. True blue flowers are hard to find. I couldn’t understand why our friends, avid gardeners, wouldn’t want to grow something so lovely.
It turns out that there are morning glories, and then there are morning glories. When different plants share the same common name, the result is all sorts of confusion. In this case, there are over 1,000 species in the family Convolvulaceae—and taxonomists are currently rearranging them all. No wonder we’re mixed up!
After some discussion, I determined that our friends were thinking of the weed known as wild morning glory or field bindweed (Convolvulus arvensis). I’ve written about bindweed in the past—it’s a perennial vine with a massive storage root that reaches to the earth’s mantle, side roots that reach 30 feet in length, and runners that pop up yards away. It’s nearly impossible to eradicate, short of a direct hit with nuclear weapons. We do well to shudder.
On the other hand, I grow the pretty blue flowers of Ipomoea purpurea. This morning glory is an old-fashioned annual, dying when temperatures dip below freezing, so they’re not going to come back next year to haunt me. Yes, they can reseed with some enthusiasm, which they did for a few years in my greenhouse, but the seedlings are easy to pull out and it wasn’t that hard to regain the upper hand. More often, the seedlings are killed by a late frost and I’m scrambling to replant. (That’s why I put them in the greenhouse in the first place.) If you’re concerned, deadheading will eliminate the formation of seed pods.
Ipomoea purpurea is a vining plant that climbs by spiraling around a support such as a fence, or strings running from the soil to the eaves. It lacks tendrils, so you may have to use some twist-ties to help larger plants hang on. The stems eventually reach over six feet in length. (A different, short-vined species, Convolvulus tricolor ‘Royal Ensign’ [left] only grows to about 18 inches, and is ideal for the front of the garden.)
Morning glories have trumpet-shaped flowers, often with white centers, that cover the vines from mid-summer to frost. Traditionally, they’re a pure sky blue, but breeding has also produced hues ranging from white, pink, and purple, to a deep wine red. Some newer cultivars (‘Carnevale di Venezia’ is one example) have streaked petals. ‘Cotton Candy’ has looks completely different, with its pink ruffled petals. They’re pretty, but I’m a sucker for the blue ones, especially the heirloom ‘Heavenly Blue.’ True to their name, the flowers open first thing in the morning, then fade as the day wears on.
The dark green leaves are heart-shaped, and slightly smaller than the blossoms, which can reach five inches in diameter. The profusion of flowers on an attractive vine makes these morning glories a perfect complement to an informal flower garden.
Morning glories are best grown from seed, directly planted where they are to grow. The seeds are slow to take up water due to their thick, hard seed coat; filing a nick in them allows water in and speeds germination. Soak the filed seeds for 24 hours, then sow them ¼-inch deep in a sunny spot around your last average frost date. There’s no point rushing the season, as they won’t sprout until the soil warms into the 60s.
Like most garden annuals, morning glories prefer fertile loam, but will grow in less than ideal soils as long as they’re kept moist. Established plants will wilt when they’re thirsty, but it’s best to water before that happens. A three to four inch layer of mulch around the roots will help, as well. Most of the time, morning glories are pest-free.
You should be aware that morning glory seeds are poisonous, containing a chemical called Lysergic Acid Amide (LSA), which is closely related to LSD, and has a similar effect. (Don’t try it; there are side-effects, some of which can be dangerous.)
There are numerous other cultivated species of morning glory. Most are not hardy in cold-winter areas, and many are invasive in tropical climates. If you’re inspired to choose a different morning glory to grow, be sure to do your homework first.