The Garden Guru: Worry-free loosestrife loves soggy soil

Posted Monday, Jun. 24, 2013  comments  Print Reprints
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It’s one of my favorite Texas garden perennials, yet compared with day lilies, daisies and coneflowers, purple loosestrife is a newcomer. You seldom saw it in Texas landscapes in the ’60s and ’70s, and only in recent years has it become even the least bit commonplace. But that’s here. In other parts of America, it’s actually a bit too commonplace. We’ll address that concern in a couple of moments.

The things that make lythrum such a valuable landscaping perennial are that it blooms in the summer in cooling bright pink or purple shades, and that it produces vertical spires of its showy flowers. They add height and drama to perennial borders that otherwise might be dominated by the somewhat formless likes of day lilies, Shasta and gloriosa daisies, coneflowers, and mallows. Loosestrife has a more defined form to its growth.

Buy purple loosestrife transplants in local retail garden centers now. You’ll find them with their other perennials, probably in 1-gallon containers and almost assuredly in flower. Figure on planting the clumps 16 inches apart to allow them to grow and fill in.

You might want to call ahead to be sure your favorite stores have them in stock. Once you have them established, you’ll probably be so satisfied with their performance that you’ll want to add more. You can dig and divide the mature clumps into several new plants every few years if you wish, or you can always leave them in place and buy additional plants for other beds.

Plan on purple loosestrife growing to 24-30 inches tall, slightly taller in really moist soils. Give it full or nearly full sun, and plant it in rich, highly organic soil. Nitrogen will encourage it to grow taller and stronger, so its flower spikes will be all the showier. Once it’s through blooming, trim off the spent flower heads to remove any seeds that might form and to keep the plants tidy. The top growth will die back to the ground with the first cold days of late fall, then return spring after spring.

A plant that’s known by the common name of “purple loosestrife” is probably going to be purple, right? Well, not necessarily. The most common variety you see around town each June is “Morden Pink,” and it has obviously parted its way from the purples. “Dropmore Purple” gets you back to the deeper shades, and you’ll find other selections in a rainbow of pinks-into-purples.

If you have a really moist spot in your landscape, perhaps down at the bottom of a hill where water seeps after rains, that would be the perfect home for purple loosestrife. It likes moist soils. It loves the wetlands.

Which brings us to that disclaimer. Lythrum salicaria is a European species that made its way into North America in the 1800s. It liked its new home, and it began to multiply. Exponentially. It is now a noxious invader in the Northeast, Upper Midwest and Pacific Northwest, where it spreads freely, crowding out the native species around lakes and in marshes. It’s actually illegal to sell it in many of the northern states, and they’re going to great lengths to eliminate it.

However, the varieties you’ll find in Texas garden centers won’t operate that way. They’re not self-fertile, so you won’t have to worry about their escaping the space where you plant them. You’ll be free to enjoy them without guilt. They’re lovely perennials that are just waiting for a place in your plantings.

And in case you’ve been wondering how a plant gets named “loosestrife” in the first place, it was widely believed that lythrum was capable of eliminating stresses and strains of everyday life — back in the 1500s!

Neil Sperry publishes “Gardens” magazine and hosts “Texas Gardening” from 8 to 11 a.m. Sundays on WBAP AM/FM. Reach him during those hours at 800-288-9227 or 214-787-1820.

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