Dividing plants is a drag but so worth the work


The biggest drawback to perennial gardening is the need to divide plants. It’s a step many gardeners avoid, although division rejuvenates the plants and controls their size.

I’m a perennial gardener, so right now I’m dividing my irises.

This job is one of the hardest in our garden, but iris blossoms are some of our favorites, so the work is worth the effort.

I started my work with the short irises that flower along with the daffodils.

Four-inch pots of sky blue, yellow and maroon irises have grown and been divided so many times over the years that the place is filled with their flowers every spring.

All of the rhizomes I dug up were healthy, so the beneficial nematodes we add to the soil to kill iris borer caterpillars is working.

Borers are the most common iris pest in Wisconsin.

Their life cycle begins when the moth lays its eggs on the iris foliage.

The larvae hatch and tunnel through the leaf, heading for the bottom of the plant.

The larvae develop into pinkish caterpillars that chomp their way through the rhizomes that support the iris leaves.

Damaged rhizomes are prone to bacterial rot, which can kill irises. Mature caterpillars move into the soil in autumn to pupate, then emerge as moths the following spring to repeat the cycle.

Short spring irises and Siberian irises are the least likely to host borers.

Dividing the short spring irises was a snap since they have shallow roots.

Pull a fan loose, clip the foliage and put the new plant in the soil. Repeat as needed and discard the extra rhizomes.         

The tall German irises are the latest to go under the shovel.

With the rhizomes right on the surface, it seems like they should be as easy to unearth as the short ones, but the roots go about 10 inches into the soil.

It was hard digging for me.

I tossed out at least a bushel of each color even after I transplanted a bunch to a new bed.

We rarely have any borer damage, and the plants spread rapidly when they’re happy, so there are always more irises than we have room to use.

Next up are the reblooming irises in the front border.

I should get them right now, but if I do they won’t flower in October.

The rain on Monday may have decided the question, however, since it’s so easy to dig when the soil is moist.

Our water-loving Louisiana and yellow flag irises were divided last year.

Even when planted in the garden soil, these irises march right into the water if given the chance, so they’re some of the toughest plants to divide.

The chance of puncturing the pond liner makes it dangerous to get too rough tearing them out.

 When the irises are settled, the dividing work is done here for this year.

Next year, hostas and the upright sedum need to be divided.

It will be a big job, but the hostas in particular are satisfying to make into new plants.

Dividing plants is sometimes hard work, but it has enabled us to build our garden, division by division, year by year and share plants with our friends as well.

Most plants only need dividing about every three years, so with planning, the job can be spread out.

Perennial plants are a great investment, and despite using annuals in containers, I expect they will always be our focus.



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Wisconsin’s largest paid circulation community weekly newspaper. Serving Port Washington, Saukville, Grafton, Fredonia, Belgium, as well as Ozaukee County government. Locally owned and printed in Port Washington, Wisconsin.

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