Regional Gardening Reports :: National Gardening Association

In the Garden:
Pacific Northwest
May, 2007
Regional Report

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This iris bed is in dire need of renovation because lilies and lavatera are producing a riot of color but running rampant over the poor iris.

Dealing With Overgrown Perennial Beds

Although I designed my perennial borders to be permanent, in reality they are works in progress. Sometimes plants aren't satisfied with their allotted space, or I get tired of them and want to try something new. And there are always overgrown beds with plants in need of rescue. Occasional tinkering to right a wrong works for a while, but eventually a major renovation is needed.

When to Renovate
The cooler soil and air temperatures of spring and fall provide the best conditions for digging and transplanting perennials. The plants suffer less stress, and the natural rainfall helps ease their transition to a new home. I choose springtime over fall because my energy and enthusiasm are highest then, and plants have the whole summer to recover and fill in any gaps.

Empty the Bed
The first step in renovating a perennial border is to empty the bed of plants. I cut a circle around the crown of each plant with a spade, then pry up the roots with a garden fork. As I remove plants, I set them on a tarp spread out in a shady spot and sprinkle them lightly with water to keep the roots from drying out.

Amend the Soil
Once all the plants are removed, I rejuvenate the soil by digging in organic matter. I spread a 4- to 5-inch layer of compost over the soil surface, sprinkle 1 cup of granular 10-20-20 fertilizer per 100 square feet of bed, then mix it thoroughly with native soil. I try to dig the organic matter in at least 18 inches deep. Finally, I rake the soil smooth, stepping as lightly as possible on the bed to avoid compacting it.

Divide and Transplant
Not all plants need dividing, but renovating a bed is a golden opportunity to increase your stock of favorite plants. Dividing plants not only produces new babies, but it also keeps plants growing vigorously. Most plants that can be divided are tougher than you think and quite forgiving if you accidentally mash the foliage. I tug the roots apart with my hands, cut with a knife, or chop away with a spade or axe, depending on root mass density. Woody root masses are the biggest challenge, but they all come apart eventually with persistence. Once separated, each little plant is placed in the bed.

Mulch and Water
The final step in renovation is to top the bed with a 2- to 3-inch layer of organic mulch. You can use shredded leaves, aged compost, or finely chopped bark to help suppress weeds and slow evaporation of soil moisture. Once the mulch is in place, water thoroughly. I use a watering wand to provide a gentle shower, sweeping it back and forth until I'm sure the soil is saturated.

When all this is done, it's time to sit back and relax. Plants will begin to recover and produce new growth in one to two weeks.

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