Has that day lily or iris you planted a few years ago gotten huge this summer? With the great moisture last winter, my perennials took off this year and have now outgrown their space.

Those perennials that you thought were “plant once and forget” aren’t so easy when they are happy and become well-established. In general, perennials need to be dug up, divided and transplanted every three to four years.

There are many reasons to divide your perennials on a regular basis. One of the most important is that it keeps them healthy as you can discard diseased, dead or dying sections. Dividing also keeps them from overcrowding, which can stunt or eventually kill your plant. And finally, the bonus is that you get more plants for your garden or to share with family and friends.

As a rule of thumb, plants can be divided in either spring or fall, so now is the perfect time. If you are unsure which plants can be divided now, think about that plant’s bloom time. Divide plants that bloom in the late summer or fall during the spring season and divide perennials that bloom in the spring and early summer during the fall.

Begin this process when the plant looks good and is healthy. Waiting until a plant becomes too large, the center has begun to die, or when the blooms become smaller or less vigorous generally means that you’ve waited too long. You want to wait to divide them however, until they are large enough to be able to make several clumps out of the original plant. Ideally, digging, dividing, and transplanting should be done about six weeks before the first hard freeze in your area in order to give them time to re-establish in your garden.

Start by working around the drip line of the plant. Dig deep into the soil in order to have minimal root damage. The idea is that you want to get it out with as much of the root ball intact as possible. Cleanly sever any roots that you must cut through. Angle your shovel down towards the center and lift the ball out of its space. Watering the spot a few days before digging will soften the soil and make this process much easier.

Once you have the root ball out of the ground, shake, wash, or break away as much of the soil from the ball as possible. This makes it easier to separate the clump. Divide your plants into several pieces, keeping the healthiest for transplanting. If you have a plant that the center has died out on, discard those sections and choose the ones from the edges where there is more vigorous growth. Be sure that all parts have good roots and some sets of leaves. The number of divisions you get will be determined by the size of the clump and generally, the largest pieces you want will be no more than 20-25 percent of the original.

Keep the roots protected from the sun and wind because you do not want those roots to dry out during this process. You can spray them with water, cover them with wet newspapers, or even soak them in a bucket of water. They will hold this way for a few days, but replanting as soon as possible is the best thing for the plant.

Once you have made your divisions, then prepare their new spots in your garden. Generally, dig a hole that is 1½ times as wide and deep as the root piece that you will be planting there. You may want to amend the soil that will be going back into the hole and in our area with our heavy clay or shale soils, this is especially important. Use Back to Earth, peat moss, compost or some other good quality amendment in order to provide nutrients to give your pieces a healthy start.

When choosing a new location for your splits, be sure to give them plenty of room. Perennials can as much as double, triple or quadruple in a year, under perfect conditions. If you plant them too close and they grow well, you may find yourself having to dig them up as soon as next year and divide them again.

Plant the division at the same depth as they were growing before you dug them up and water well. You may want to add a top layer of mulch to help conserve moisture. This will help the plant to establish itself more quickly and keep it from drying out if we have a late warm or windy spell. Dividing can be stressful on the plants, but they’ll recover quickly in the right conditions, so be sure to keep them well watered after transplanting. You don’t need to worry about fertilizing now – fertilizer promotes top growth when what you need at this point is for them to simply root in well.

I’m an iris lover so many of mine have been dug up over the years and many of the divisions go to the garden center to be potted for sale the following spring. If you have variegated iris that smells like grape soda pop, you probably have a piece from my garden. Although perennials aren’t as “plant once and done” as many people think, they are well worth the effort. When they are healthy and thriving, there’s nothing more beautiful than a well tended perennial bed.

Gail Vanik can be reached at 970-565-8274 or by email at fourseasons@animas.net.