Many of Mississippi’s perennial landscape plants will start to decline after several years. That means they will have smaller foliage and won’t flower as much, even though they’ve been well cared for with regular fertilizer and irrigation.

Most of the time, the change in growth is due to the perennial becoming crowded. Just recently, someone asked me why an older clump of Louisiana irises are not performing like they used to, and my answer was that the plants need to be divided.

Described as garden surgery, division is simply cutting up the plant into smaller pieces and replanting them. Dividing perennial plants is a great way to rejuvenate and renew some of our garden treasures.

You do not need special tools for dividing plants. A garden spade or fork, a serrated knife like a weeding or soil knife, and a small saw are generally all you need to get started. But one thing is necessary for all your garden tools: They must be sharp!

Just as sharp knives are essential in the kitchen, sharp garden tools are essential for any landscape job. Dirt, rocks and tree roots quickly dull garden tool edges. You may have never sharpened your garden spade, but believe it or not, a sharp spade actually makes digging easier.

Sharpening your garden spade is really easy.

You’ll need a 10- or 12-inch bastard cut mill file, which is readily available at home centers and hardware stores. This is a good all-purpose choice for sharpening any garden tool. Make sure the file lays flat across the edge bevel. It sharpens only when you push it, not when you pull it back, and that makes the file easy to control. It takes only a few long strokes to get a good edge.

You can watch me demonstrate garden tool sharpening in the Southern Gardening TV segment, Sharpening Your Tools, http://extension.msstate.edu/southern-gardening/video/2018/sharpening-your-tools.

I try to divide my perennial plants about every 3 to 5 years, depending on the perennial. To begin, carefully lift the entire perennial with most of the root system out of the ground using your garden spade or fork. This will cause less damage, and you will be able to make more divisions.

Identify the growing points. You may have to use your fingers to find the spots where the division cuts are to be made. For the greatest success, make sure all divisions have a growing point and attached roots.

When replanting, prune off about half of the foliage. This will reduce water loss as the roots begin to regrow. Plant the crown of the division at the same level it was in the ground on the original plant. Arrange the pieces in a random fashion so they do not all grow in the same direction.

While most perennials can be divided at any time of the year, spring and fall are considered the optimum times to do this gardening task. Flowering behavior indicates the best times to divide.

Divide spring-flowering perennials in the fall and summer, and divide fall-flowering plants in the spring. After planting, apply a layer of mulch and keep the divisions well watered until the roots become established. Hold off on fertilizing until you observe new growth is.

You’ll probably end up with more perennial divisions than you can use, so be sure to gift a few to your friends and neighbors.