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Morning glories, moonflowers, and their relatives

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One of my favorite summer memories is from the first year I planted moonflowers. My husband-to-be and I had rented a tiny cottage in a seashore town on the eastern end of Long Island. Having been without a garden the previous few years when I lived in the city, I planted a tiny one in front of our pint-size cottage. I put up some strings and planted moonflowers and ‘Heavenly Blue’ morning glories to climb up and around the front porch. In the daytime, the porch was shaded by the vines and festooned with the big azure morning glories. Late in the afternoon the moonflowers opened, and on hot summer nights their enchanting fragrance filled the porch and drifted into the house. It felt like a little piece of paradise, and I've planted morning glories and moonflowers every summer since then.

Morning glories and moonflowers—as well as a host of other attractive species and hybrids—are members of the genus Ipomoea, a group of 450 species belonging to the Convolvulaceae, or morning glory family. The name Ipomoea comes from the Greek ips (worm) and homoios (similar), in reference to the plants’ climbing or trailing habit. They are twiners, and some of them can reach 20 feet in a single summer. Ipomoeas come from the tropics, and they thrive in warm weather. Although many are perennial in their native habitats, we grow them all as annuals in our Temperate Zone gardens. Occasionally they are confused with species of Convolvulus, the bush or dwarf morning glory, or the insidious wild bindweed, both of which are related. All have flowers whose petals are fused into a tubular or funnel-shaped corolla, and their seeds are poisonous if ingested.

A COLORFUL TRIO Three closely related species—Ipomoea nil, I. purpurea, and I. tricolor—are all called morning glories. They reach eight to ten feet long or more, with heart-shaped leaves from four to six inches across. The flowers have a wide, fluted corolla and a long, tubular throat that is white or pale yellow in some cultivars. Although each blossom lasts just a single day, opening with the rising sun and closing in the afternoon, the plants produce lots of them right up until frost. (See the chart on page 42 for a description of individual cultivars.)

Ipomoea nil is woody-based in the tropics, and has sometimes been called the white-edged morning glory. The broad, ovate leaves are usually entire but sometimes three-lobed, and grow to five inches long. The flowers may be mottled and streaked, edged in white or another color, ruffled or scalloped along the edges. Very similar to I. nil is the large-flowered imperial Japanese morning glory (I. ximperialis).

The common morning glory, I. purpurea, is native to Mexico but has been much hybridized. It usually self-sows in my garden, and the self-sown flowers are almost always purple or a rosy magenta; they can be a pest in a tidy, orderly garden, but I don't mind them in mine.

Ipomoea tricolor has given rise to the perfectly named ‘Heavenly Blue’, a 1930s heirloom whose breathtaking blossoms are exactly the color of a clear autumn sky, as well as a handful of other eye-catching selections.

Morning Glories

TYPE OF PLANT: tropical perennials grown as annuals FAMILY: Con-volvulaceae (morning glory family) GROWTH HABIT: twining climbers HEIGHT: to 20 ft. or more, depending on species LEAVES: heart-shaped, lobed, or finely divided FLOWERS: funnel-shaped, 3-6 in. across (most varieties); wide range of colors BLOOM PERIOD: summer until frost EXPOSURE: full sun SOIL: light, moist, well-drained WATER NEEDS: moderate, regular; drought may reduce bloom FEEDING: usually not necessary; apply low-nitrogen fertilizer if plants seem weak PROPAGATION: by seed SOWING: soak seeds overnight in warm water; sow indoors 6-8 weeks before last frost or directly outdoors after soil has warmed to 65°F; cover seeds with 1/4 in. of soil PROBLEMS: tortoise beetles may attack foliage; control with insecticidal soap

Morning Glory Cultivars

I. NIL CULTIVARS: ‘Chocolate’ — reddish-brown flowers ‘Early Call’ — pink, rose, blue, white, lavender mixture; some flowers have white edges ‘Scarlett O'Hara’ — wine-red flowers with white throats; attractive to hummingbirds ‘Scarlet Star’ — cerise flowers with white star in center

I. xIMPERIALIS CULTIVARS: ‘Blue Silk’ — soft blue flowers with white stripes and edging ‘Minibar Rose’ — rosy crimson flowers with white throat, sometimes central star and edging: lobed, variegated leaves ‘Mt. Fuji Mix’ — pale blue, purple, deep violet, pink, and crimson mix with white stripes and edging; lobed, variegated leaves ‘Rose Silk’ — soft pink flowers with picotee edge and white throat; variegated leaves ‘Tie Dye’ — lavender flowers striped with deep purple in varying patterns

I. PURPUREA CULTIVARS: ‘Crimson Rambler’ — rosy burgundy flowers with a white throat; heirloom ‘Grandpa Ott's’ — deep purple flowers with a wine-red star; heirloom ‘Kniola's Black’ — deep blue flowers with a white throat ‘Milky Way’ — white flowers with five carmine stripes ‘Morning Star’ — purple, violet, blue, rose, pink, and white mix with white throats and contrasting star

I. TRICOLOR CULTIVARS: ‘Blue Star’ — light blue flowers with a darker blue star ‘Flying Saucers’ — white or pale blue flowers streaked with violet ‘Glacier Moon’ — pale ice-blue flowers ‘Heavenly Blue’ — sky blue flowers; heirloom ‘Pearly Gates’ — pure white flowers ‘Wedding Bells’ — lavender-pink flowers

THE MAGICAL MOONFLOWER Ipomoea alba, sometimes listed by its old name, Calonyction aculeatum, is the morning glory's nocturnal counterpart. It has the lush, heart-shaped leaves of a morning glory and big, white, irresistible flowers (those of ‘Giant White’ are six inches across). The corolla is wide and flaring, with a slight tinge of green on the outside. The fragrance, to my nose at least, is sweet but not cloying—a pure delight. The flowers open in the late afternoon or early evening, stay open all night to attract pollinating moths, and close the next morning. The vines can grow to 40 feet in the tropics, but reach about 10 feet in one of our Long Island summers. Moonflower is an heirloom—it's been listed in catalogs since the 1800s.

SCARLET STARLETS AND “EXOTIC LOVE” Cypress vine (I. quamoclit, formerly Quamoclit pennata) is a far more delicate-looking plant than the more robust three just described. It is distinguished by leaves that grow about three inches long and are deeply cut into thin, almost threadlike, segments. Often confused with cardinal climber, its flowers are similar but the leaves are decidedly different. A true annual, its slender vines can reach 20 feet in a summer. Star-shaped, bright scarlet flowers with narrow tubular throats, about one and a half inches long, deck the vines from midsummer to frost. Cypress vine is too fine to cover an ugly fence, but it can produce a filigree of greenery on a slender trellis and a surprising shot of color if you train it on an evergreen shrub. ‘Maiden's Feather’ has flowers in rose, pale pink, and white, in addition to the usual scarlet.

The similar cardinal climber (I. xmultifida) also has small scarlet flowers, but its leaves are deeply cut, almost to the midrib, into as many as 15 pointy, narrow leaflets that give it a ferny look. The leaflets are narrow but not as thin as those of cypress vine. The tubular flowers are pentagonal when seen face on, and they have a white eye. The slender vines grow to 10 feet, and are better used for decoration than camouflage.

Less known is scarlet starglory (I. coccinea), also called crimson star flower or red morning glory, an apt description of its flowers. They are small, funnel-shaped, bright red with a yellow throat, and carried in racemes. The leaves are large and heart-shaped. Grow scarlet starglory in a hanging basket, or plant it to climb a trellis, arbor, netting, strings, or wires.

One more old-fashioned ipomoea has been grown for years but is a more recent addition to the genus. Spanish flag, named because its colors echo those of the flag of Spain (and now also known in some quarters as “exotic love"), used to be classified as Mina lobata but is now Ipomoea lobata. Its leaves are divided into three long, pointed lobes with two or three smaller lobes at the base. The color-changing flowers are not flashy, but they certainly are entertaining. Small and tubular, they are carried in loose spikes (that look more like sprays) about four inches long; each flower is about an inch long. They don't have flared petals like other species; these are narrow tubes with long stamens. The buds are red, the flowers open scarlet, then fade to orange, yellow, and eventually, cream. Spikes often contain all the colors at once, and the blossoms keep on coming all summer, right up till frost. ‘Citronella’ has yellow flowers that fade to creamy white.

FIRST-RATE FOLIAGE This venerable genus is also home to a vegetable—the sweet potato (I. batatas), which has given rise to some ornamental cultivars grown for their interesting foliage in the North. These plants cascade or sprawl rather than climb, and make terrific companions for summer flowers in tubs, pots, and hanging baskets, or scrambling around their feet in an informal bed or border. ‘Blackie’ has dark purple-black leaves that are deeply palmately lobed, and stems that grow 6 to 10 feet long, depending on the length of the growing season. It is lovely with flowers of soft pink or pale yellow, and a showstopper with tropical reds and oranges. ‘Margarita’ is chartreuse (more yellowish in full sun, greener in partial shade), with more heart-shaped leaves with three broader lobes; the leaves are thinner in texture than those of‘Blackie’ and, unfortunately, at my house the slugs love them. I like ‘Margarita’ with blues and violets or with gold and orange flowers, and it flourishes as long as I don't let the leaves trail on the ground. ‘Tricolor’ has lobed leaves that blend green, pink, and creamy white.

GROWING THEM Morning glories and their relatives are easy to grow and adaptable to a range of soils. I've grown them in Pennsylvania clay and Long Island sand. They all need warm weather and plenty of sun (except for the sweet potato vines, which can handle partial shade), and they do best in soil that is light, moist but well drained, and of just average fertility. Don't overdo the nitrogen—one year when I put too much manure on the garden, the morning glories produced luxuriant leaves but fewer than usual flowers.

Sweet potato vines are best purchased as young plants or started from cuttings. The others all grow readily from seed. The seeds, though, have a hard coat that slows germination, unless you nick them with a file (a time-consuming procedure, to say the least), or soak them in lukewarm water overnight before sowing. I've found that soaking works just as well as scarifying, and it's a lot less trouble.

For years I direct-sowed seed because ipomoeas don't generally transplant well. But the cool springs on my part of Long Island prevented me from planting them until nearly Memorial Day, and some years the moonflowers didn't bloom until almost October. These plants won't get going until the soil is warm. I finally wised up, and now sow seed indoors in peat pots six to eight weeks before the last frost. A helpful trick is to insert a small bamboo stake into each pot when the seedlings are about three inches tall to give them something to climb on and to keep them from getting tangled.

The recommended spacing in the garden is 8 to 12 inches. I tend to plant them closer together and turn the plastic netting on the north side of the vegetable garden into a wall of flowers and foliage. You can also train the vines on an arch or arbor—large-leaved varieties are great for making shade in a hurry—or use trellis or netting. Or plant them alongside a shrub and train the vines up into its branches. For a real laissez-faire approach, let the vines scramble around on the ground. I'm thinking of planting some morning glories out on the berm at the end of the driveway this year, to keep the sweet autumn clematis company as it roams around by the street.

Training Morning Glories

STEP 1: Select a warm, sunny, well-drained site. Loosen the soil to a depth of about 10 inches and work in several inches of compost. If some sort of support is not already in place, set it up before transplanting the young vines. Space the plants from 6 to 12 inches apart. If you are transplanting seedlings in peat pots, plant them deep enough so that the edge of the pot is buried, or tear off any portion of the pot that remains exposed. Otherwise the rims can wick moisture away from the roots.

STEP 2: To encourage the vines to grow in the right direction, lean the bamboo stake (if you are using one) and vine toward the permanent support. If you have not used a stake to train the seedlings (and sometimes even if you have), you may find it necessary to tie the stems to the support with soft string or flexible ties until they begin twining.