Though the days are getting shorter there are still plenty of chores to do in the garden before fall arrives and the season of distraction pulls us into the land of pumpkin spice everything. Before you succumb to cider and gourd shopping, spend some time with your perennials.
Perennials are low maintenance in fall, with just a bit of mulching and up debris. But older plants start showing their age, developing a dead center or slowing down on flowering. Still others expand to try and take over real estate that shouldn’t be theirs. These are all signs that your plants need to be divided.
Most perennials are divided in spring, but for those that flower at that time, division in the fall is best. Hosta, Phlox, Rudbeckia, and Veronica are a few of those that tolerate fall division. September is the ideal time in Colorado to divide these plants in order to allow six weeks or more after replanting for re-establishing roots before the ground freezes.
All you need is time and a bit of muscle to divide your plants. Here’s how:
• Basic tools include shovels, spades, garden forks, a large sharp knife, pruners, and gloves. You might not need all of these tools – each plant will vary – but it’s fun to lay them out like a surgeon’s tray and croon “it’s time, my lovelies” at the plants. Make sure shovels and spades are sharp, and all tools clean.
• Water all plants to be divided a day or two before division, slowly soaking the soil to help it loosen before you dig.
• The best type of day is a cool, cloudy one to help minimize the shock to the plant. Mother nature isn’t cooperating yet on sending these our way but check your weather app to gauge which day holds the best promise.
• Trim back the foliage on taller plants before dividing. This helps prevent eye injury from stems whipping back and forth as you move and cut the plant.
• With the garden fork or spade gently loosen a circle six to twelve inches from the base of the plant, then dig under the plant and lift it, preserving as many roots as possible. Gently remove the majority of the soil by lightly shaking or washing the root ball.
• If the center has died out, cut off the dead area and divide the remaining, healthy plant into sections with a sharp knife or pruning shears. Leave a minimum of two to three growing points on each new clump.
• Prepare the soil in the planting area by refreshing it with compost and turning it so that it is light and fluffy. Plant the divisions and keep them moist until they re-establish. If the divisions will not be immediately planted, keep them cool in a shaded area and the roots moist.
Summer and fall blooming plants should be divided in the spring before they begin to grow, ideally as soon as the growing points emerge. Iris and daylilies are best divided a few weeks after they have flowered for the season. Others like bearded iris or daylilies simply need rejuvenation every three to five years.
By Carol A. O’Meara. Carol is an Extension Agent – Horticulture Entomology at Colorado State University Extension Boulder County. For more information contact CSU Extension at the Boulder County Fairgrounds, 9595 Nelson Road, Box B, Longmont, 303.678.6377, e-mail firstname.lastname@example.org or visit ext.colostate.edu/boulder.