Q. Why did you have a plant exchange in August? I’ve always been told to divide in late fall or in the spring. It seemed silly to me.
Mabel from Canfield
A. When we hear gardening information from others, we should always wonder where they get their information. Is it research-based? Have they had success more than one year with the recommendation?
I get this question nearly every year that I have held an August plant exchange. Simply put, the roots of perennial plants need time to adjust to their new home and get settled in for the winter. If you wait too late in the fall, they may not have the chance.
Roots need time because they can be affected by ground heaving — the effect of freezing on the upper layer of soil. When we have lots of temperature swings in the winter, the top soil moves up and down with the freezes and thaws. This heaving action can cause plants to pop out of the hole you dug for them, and the roots freeze. Sometimes the plant dies all together. Other times, the plant is reduced in size or vigor for next season.
Perennial plants commonly affected by this heaving include: pincushion flower (Scabiosa); coral bells (Heuchera); shasta daisy (Leucanthemum); blanket flower (Gaillardia); pigsqueak (Bergenia); coreopsis (Coreopsis); whirling butterflies (Gaura); foamy bells (Heucherella); garden mum (Chrysanthemum); and painted daisy (Tanacetum), to name just a few.
Many other plants should be divided just so the plant can prepare for spring and early summer blooms next year, including bleeding heart (Dicentra); daylily (Hemerocallis); hardy geranium (Geranium); hosta; iris (Iris sibirica and other hybrids); and many more.
In general, if the plant is done blooming, you can divide it. The bigger issue is making sure the new plants are planted properly, watered regularly and mulched in for the winter.
For more information, visit go.osu.edu/divideaugust.
Eric Barrett is the OSU Extension Educator for Agriculture and Natural Resources in Mahoning County. Call the office hotline at 330-533-5538 Mondays and Thursdays from 9 a.m. to noon to submit questions.