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Don Kinzler, Published June 21 2013

Growing Together: Imagining the Iris: Proper weeding key to thriving perennials

Good news: Gardening participation is up with a surprising new twist.

The recent National Gardening Association survey shows another yearly increase, but interestingly the largest boost in spending for garden products came from 18 to 34 year-old males.

If you participate in some form of growing, you now join 85 million other households nationwide.

Expenditures on vegetable gardening rose for the sixth straight year and have now topped flower gardening in dollars spent. Average annual spending on horticultural products is $347 per household.

June is a visible garden month, and I couldn’t resist the compulsion to write about irises because they have been superb recently. Yes, I know, I wish they bloomed all season.

But irises are like most perennials: They have a specific bloom period lasting from two to four weeks.

That’s why the best perennial flower beds include an assortment, extending from spring tulips through fall mums. Perennial flower beds are continually changing, adding to their intrigue.

Irises are best dug and divided in August. We are usually not thinking iris at that time because their bloom is long gone, and we’ve forgotten that we wanted to ask Grandma Erma if she would share.

Potted irises from a garden center can be planted all season, which reminds me of a gardening note of caution.

When a perennial is actively growing in a pot, the roots should be disturbed as little as possible when transplanting into the flowerbed. Prepare the planting hole, then carefully slip the plant out of the pot keeping the soil ball intact. Water first if dry. If there are circling roots, gently slice through the outer surface. Plant, and water immediately. Don’t let the plant even think about wilting.

Perennials already established in a flowerbed might die if dug and divided in active growth. That is why the operation is best done during their dormant time. If you absolutely must move a perennial during the wrong time, do it quickly and gently, keeping a soil ball around the roots. Water immediately after planting. Act as though the plant is bleeding to death and you need to get it to the emergency room, STAT.

The most common iris is the Bearded Iris, also called German Iris from the species name Iris germanica. Almost any color is available. In case you’re asked during a trivia game, the name iris is derived from the Greek word for rainbow.

Two other species well worth growing are Siberian and Spuria iris. Both create nice clumps of taller, narrower foliage, which is dramatic in the landscape. Flowers are smaller than Bearded Iris but delicate and beautiful.

Bearded Irises are best divided every three or four years in August. Otherwise the center of the clump thins out and decline begins.

Iris “roots” are actually a fleshy rhizome with the true hair-like roots extending below. The fleshy rhizome should not be covered with more than a half inch of soil. Mound the area slightly for good drainage.

Irises are typical of most hardy perennials. During our greenhouse decades, my wife Mary and I were often visited by well-meaning gardeners who desired to plant perennials because “they wanted something that came up each year so they wouldn’t have all the work.” That’s a bit like thinking the work is over once the baby is born.

The most laborious part of perennials is weed control, especially several years after establishing a new bed. Weed seeds sprout. Rhizome sprigs of quack grass and thistle start to multiply. Dandelion roots produce, and dandelion seeds establish. Tree seedlings start their century of life among your plantings.

Weed control in perennial flowers takes a four-pronged approach.

First, hand-weeding, pulling, hoeing, and persistence works.

Second, Roundup is great if we read instructions. It kills all actively growing plants, including your lawn grass and the neighbor’s roses.

Try a cloth glove dipped in Roundup solution and worn over a plastic glove to stroke the weeds to their death. If spot spraying, use a cardboard shield next to plants you don’t want to kill. Another herbicide, Grass-Be-Gone, kills grassy weeds without harming perennials. It works, but slowly.

Third, Preen is a very useful pre-emergent granular herbicide that prevents seeds of weeds from establishing. Use it after the perennial bed is clear of weeds. It only stops seeds, not stop weeds from sprouting from roots, as is common with quack grass and thistle.

Fourth, a two- or three-inch layer of mulch reduces weed competition and conserves moisture. Use wood chips, wood shavings or compost.

I suppose perennial life would be easier without weeds, but it does allow us to commiserate about something other than the weather. After all, we continue to “Grow Together.”

Don Kinzler, a lifelong gardener, worked as an NDSU Extension horticulturist and owned Kinzler’s Greenhouse in Fargo. Readers can reach him at donkinzler@msn.com.