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As I sat in Starbucks with friends one day, I was bragging about a romantic bower I had created with twiggy saplings and Morning Glory vines. The woman at the next table interrupted me, saying sarcastically: "I don't know how you can rave about such an awful weed. Don't you know any better?" She stomped away and I took a deep breath. "Aha," I said, "What we have here is a clear case of Confusion Of Common Names!"
Offhand, I can think of three distinct plants that are commonly called Morning Glory. Two are dreamy beauties to ornament the border and the other one is a nightmare-truly the monster under the flowerbed. The trick is to tell them apart and cultivate the good ones while eradicating the thug. I'll start with the bad guy- Convolvulus arvensis (aka Hedge Bindweed and Wild Morning Glory).
This plant is a hardy perennial with thick, white roots that go for a long way deep under ground (like completely under the house) and it climbs very fast once it pops up in the garden. It has heart-shaped leaves and white or pinkish-white trumpet flowers. It is often found in wastelands and roadsides. It likes crusty, sandy or stony soil, but it can also be a pest in the thickest gumbo clay. Once it begins to twine around your ornamentals, it will choke off the sunlight and steal the water. If you don't remove it completely, it will engulf your garden. Farmers detest this weed with passion-it can ruin a harvest in short order.
To control it, you must (a) remove all of the top growth (but don't compost it until you are SURE that it is really dead, seeds and all) and (b) kill the roots. Don't hoe, dig or till the ground while there are still live roots since every small fraction of root will survive and make a new plant. You can hand pull from now until the next millennium and not get them all. Smothering with a thick mulch is only moderately successful-the roots live a long time without light and travel many feet before they pop up like a cartoon villain in some new locale.
This is one plant that I will attack with glyphosate (sold as RoundUp and in other brand names). Mixed according to package directions and applied extremely carefully with a sponge brush to each new shoot, glyphosate can knock Convolvulus back to near zero in about two growing seasons. You have to go around the garden about once a week at first, tapering to monthly after the worst is gone. RoundUp is most effective on morning glory after it blooms and colder weather is setting in, because it's pulling nutrients down to the roots for winter and it will absorb the chemical.
Now for the very good guys. The beautiful morning glories are tropical annuals. Ipomoea tricolor is the climber (going 10 to 15 feet) and Convolvulus tricolor is the dwarf, bushy type. Unlike their namesake, these plants only grow for one season and are a little tricky to get going here in the cloudy, cold Northwest. In the Midwest, climbing Ipomoea is called "mailbox plant" for its common use scrambling over postal boxes. But without summer heat it can sulk for days without a blossom. Don't plant it too early. The seed coat seems to repel water and it won't germinate unless you either score it with a knife or sandpaper a thin spot using an emery board. It doesn't like root disturbance, so transplanting seeds started in pots is chancy-it's best to plant the seed in its permanent home in the hottest, sunniest spot you have. Good fertile loamy soil works best. Unlike the weed, which survives no matter what, the annuals must be watered in dry spells.
All of this effort pays off when the flowers come. They are delicate fairy-like trumpets in shades of pale blue ("Heavenly Blue"), deep purple blue ("Grandpa Ott"), striated lavender and pink ("Flying Saucers" or "Tie Dye") and a variety of pinks, purples, mauves and soft reds. Each bloom has a star shape in the center. Some stars are very distinct and yellow while others are just soft shadows. The dwarf form has an even broader range of flower color with banded blossoms in blues and yellows as well as the reds. Sensational!
I'm going to try growing the climber in a large tub on the patio this year. It's a protected microclimate and the cement floor reflects heat well. My fingers are crossed-I hope for another romantic bower to dream in.
Hortsense: Managing plant problems with Integrated Pest Management
