It's a Good Time to Dig, Plant Perennials

By for CAES News

The next few weeks will be the ideal time to plant new perennials or divide and relocate established perennials in Georgia.

By allowing the plant to reestablish its root system during October, November and December, perennials are then well-prepared to endure our winters. A well-established root system will support rapid growth and optimal flowering the following spring.

There are several reasons to relocate or at least divide and replant perennials. The main reason is that many, if not most, perennials grow into large clumps or colonies. Competition for nutrients, water and root space tends to reduce the vigor of the entire group.

Irises, hostas, phlox, liatrises and shasta daisies, for example, will remain vigorous if divided about every three years.

There is another reason replanting perennials is a good idea. Whether you live on piedmont clay or sandy soils, rainfall, garden foot traffic and gravity slowly compact the soils.

Annual beds, dug every spring, tend to have good porosity and air movement in the soil. Perennial beds, though, are usually left alone and need attention about every three years.

Before you do anything, take a soil test to the county Extension Service office. When you get back the lab's recommendations for amendment and nutrition, then start digging.

You can use a shovel to divide really tough perennials such as red hot poker, day lily, phlox and swamp sunflower. My experience with perennials, however, leads me to suggest you divide plants such as hosta, iris, coneflower, shasta daisy and other more fragile, clump-forming perennials by hand.

Dig up the clump at the edge of the dense root system, knock off the soil carefully and then feel through the root system for natural clusters or points of separation. Each perennial is different, but with a little feeling around, it's usually easy to do.

Pulling the clumps apart gently, with increasing force, will give you an idea if they come apart naturally or if you will need a hand pruner to cut connecting roots. My philosophy is that the fewer roots you cut, rip or tear, the less likely disease will get a foothold.

I like to let fleshy roots, tubers and corms dry out for a day before transplanting. I replant and water-in soft fibrous roots as soon as the bed is prepared. Be sure to pile up divided perennials out of direct sunlight.

Preparing the bed is simple. Add the recommended amendment, then till or dig to at least 12 inches deep. Add only a very little nitrogen to the soil so as not to push new growth easily killed by frost.

Your perennial bed soil may look mounded by 4-5 inches when you finish. This is a good sign you have done a good job. Rake the soil evenly into a smooth, slightly sloped mound.

Plant your perennials in the soft soil. Do all you can to avoid compact the soil with your knees and feet. I do this with a 3-inch-thick pile of newspapers to kneel on. Or I use a piece of plywood as a plank.

Once the planting is done, irrigate the entire bed with a sprinkler for two to three hours. The bed will settle some. Don't worry. The bumpy look will vanish by March.

After watering, cover the bed with 3 inches of pine straw to reduce erosion and rain compaction and to keep the soil cool. This will also prevent early warmup and premature growth.

Be sure to add 10-10-10 or a similar fertilizer in late spring when the new plants start growing. Remember, too, to check the moisture in the newly dug bed. If we have a dry spell in October, you may need to water.

Paul Thomas is a horticulturist with the University of Georgia College of Agricultural and Environmental Sciences.