by Charlene Burgi
The title sounds like a lesson in mathematics, but fall is the time to divide some of our plants so we can multiply our bounty of vegetables like asparagus and artichokes and add to the display of perennial color in the garden. The flowering varieties may include such beauties as lilies, iris, yarrow, daylilies and oriental poppies.
First, determine which plants need to be divided. Here are some clues: You may note that growth occurs only on the outside of the plant, leaving the inside sparse or dying. Other plants may have stopped blooming or fruiting. And still others may have noticeably smaller blooms.
After identifying which plants to target, decide where you are moving the new plants before you begin this process. Amend the soil in this area with plenty of compost and aged manure and mix this into the soil to a depth of about eight inches. (This task will be easier if you sheet mulched the area this past spring.)
On a cool day, use a garden fork to lift the entire plant clump you want to divide. Break away as much of the soil as you can. Sometimes it is easier to soak the clump in a bucket of water to separate the root system. Cut the roots with a sharp knife or instrument and remove all dead, damaged or rotted parts.
Dig a hole 1.5 times the width and depth of the divided clump’s roots. Build a firm mound in the middle of this hole and spread the roots over the top of the mound. Be certain the crown of the plant is at or just below the soil line. Backfill and gently tamp the backfilled area around the plant. Water the plant well and keep moist, not wet, until the roots take hold in the newly prepared soil (about three weeks). Do not fertilize. The amended soil will provide nutrients and encourage new root growth. Add three inches of mulch to the new plants and stand back to watch them grow.
Note: If you divided more than you can work into the ground in one day, place the divisions in the shade. Keep the root ball sprayed with water and cover with wetted newspaper for up to three days. Consider potting up your plants as gifts if you have more than you know what to do with. Garden friends and family will welcome these treasures.
I also need to clarify that this is a good time to divide iris if you have Siberian and Dutch iris; however, the bearded iris should be divided after blooming or by August at the latest. I have reblooming bearded iris and will experiment with dividing them after they finish blooming this fall.