GARDENING IN IOWA

Keep watch for invasive plants

Gooseneck loosestrife is considered invasive and can quickly overtake a garden. (The Gazette)
Gooseneck loosestrife is considered invasive and can quickly overtake a garden. (The Gazette)
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Back when I was a beginning gardener, I purposely sought out those plants that carried warning labels. These were the plants with catalog descriptions and labels that used terms like “can be invasive,” “spreads rapidly,” “vigorous reseeder,” and “multiplies readily.”

Just as a “keep out” sign can, to a certain type of youth, be taken as an irresistible invitation to go right on in, these cautions merely compelled me to purchases these plants with abandon.

After all, I had a big backyard and a small budget. I wanted to fill my landscape with tall vines, sprawling ground covers and fast-growing perennials and annuals that would quickly overflow every nook and corner.

So I welcomed all the most notorious thugs into my garden: yellow loosestrife, gooseneck loosestrife, oxeye daisies, old-fashioned morning glory, pampas grass, “ditch” daylilies, blackberry lilies, columbine, Missouri primrose, honeysuckle, trumpet vine, larkspur, silver artemesia, mint, purple coneflower, creeping jenny, alba rose and Zebrina hollyhock mallow. In the shade, I harbored ostrich ferns and creeping periwinkle.

They thrived and then some. If I planted two invasives side-by-side, they began to duke it out for dominance.

Right now in my front yard, the lily-of-the-valley is trying to overtake the bishop’s weed. Which thug is gaining the upper hand varies from year to year, depending on growing conditions. But right now my money is on the lily-of-the-valley. It’s advanced successfully enough now to force the bishop’s weed into slow retreat.

Sometimes the most unlikely plants behave invasively. It was a revelation to me the afternoon I found myself yanking out tomato seedlings that had self-sown in a flower bed.

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It was, apparently, time to revise my open-borders policy. This garden was full, and it was time to make tough choices on who was staying and who was going to be voted off my little horticultural island.

Edging was installed to control spreading. I repotted mint and pampas grass in pots sunk into the ground to contain them, like unruly toddlers into playpens. And like naughty children, they grew up and ran amok, oblivious to propriety. I had a problem plant rebellion on my hands.

I became ruthless. I dug up plants, only to find that if I left even a little bit of their roots system in the soil, they sprang right back. I cut them back, only to find that hard pruning is an excellent way to stimulate new growth, like the bittersweet that sent out runners and new vines 10 feet away from the mother plant. I smothered them with mulch. I poisoned them with Roundup. I conducted beheadings by snipping off flowers in full bloom to prevent seed production. I did everything but strangle and burn the poor innocents.

My then-young daughter watched this all with confusion. Why was mommy pulling out flowers? I explained to her that these invasive plants were plant bullies — that they took away food and water from the other flowers and so they had to go away.

This made sense to her: “So that’s why you put them in the compost heap and give them a time out!” Smart kid.

After years of undoing what I once so enthusiastically did, I am now almost on top of it. It’s amazing what you can accomplish after waging war on aggressive plants for a mere 15 years. I’ve developed an eagle eye for the tiniest sprig of pampas grass. I think I could laser-view in on one from 50 yards.

Weekly, I patrol my garden, a large jug of Roundup in one hand and the attached motorized spray head in the other. No soldier on night watch was ever more intensely alert and focused on spotting the enemy.

I have replaced many of the aggressive species with similar, less aggressive and more attractive cultivars, sort of the Stepford wives of plants.

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Gone are the rather ragged, reseeding, semi-wild oxeye daises, replaced with the more genteel, hybridized Snow Lady.

Those orange rogue ditch lilies are gone, supplanted by the highly pedigreed and tastefully colored Autumn Red hemerocallis.

Sometimes I miss my landscape’s wilder days of horticultural abandon. It’s sort of like my own college-era partying — obviously unwise but also rather deliciously reckless. I suppose it’s predictable, isn’t it? I’m older and more prudent now, and more tame, just like the garden I choose to cultivate around me.

Veronica Lorson Fowler is co-publisher of The Iowa Gardener website at theiowagardener.com.

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