Small flowers, sparse foliage, floppy plants? Time to divide

By Marilyn McKinley

OSU Ext. master gardener volunteer

Many of our favorite summer perennials have passed through their prime bloom time. But when is the best time to divide? I prefer to divide in late summer or early fall for two reasons: I am not as busy with garden chores now, and I feel dividing in late summer gives them a chance to establish good root systems for next year. In addition, you never know what spring weather may bring. Whatever your reason, now is the time to start planning for next year. Do you need or want to divide some of your perennials? Most perennials need to be divided every three to five years.

Chrysanthemums and asters may need to be divided every year or two to prevent crowding themselves into nonblooming clumps. Wait until spring to divide these fall-blooming favorites. Some perennials may do best if left alone, like peonies or bleeding hearts. They make take years to recover and start blooming again.

How do you know if a perennial needs to be divided? Don’t wait until the clump looks like a doughnut. Flowers may be smaller than usual, the bottom foliage is sparse, or the plant starts to flop and needs to be staked.

How to prepare for the divide? Water plants deeply for two days. Pick a cloudy day for the dig. Prepare the new area before you lift the perennial. Prune the stems and foliage to 6 inches from the ground. Use a sharp, clean pointed spade or fork. Loosen dirt on all four sides of the plant, about 4 to 5 inches away from the plant. Pry underneath and lift the whole clump to be divided. If the plant is very large and heavy you may need to cut it before lifting. Shake or hose off loose soil, remove dead leaves or stems.

Some perennials may be more difficult to divide because of tenacious root systems. It’s a good idea to know what type of root system you are dealing with before you dig. The fact-sheet link below will help you determine the root system on your plant, and thus the best way to divide the plant.

The planting: Never allow divisions to dry out. Keep moist until replanted. Trim broken roots before planting. Replant at the same soil level. Water deeply. Once planted, I like to side dress with compost or a 10-10-10 fertilizer.

To share some plants, join the Mahoning County master gardener volunteers Aug. 16 for our annual Bring One, Take One plant exchange at the Pumpkin Building at Canfield Fairgrounds. (http://go.osu.edu/boto). For more on dividing perennials, visit: http://go.osu.edu/divide.