From the Garden: Dividing Perennials - When, How, and What Then?

By Erin Bregalia

For the gar­den­er, the crisp autum­nal air sig­ni­fies that the hard work is done. There’s final­ly time to walk the gar­dens, inspect­ing new plant addi­tions and not­ing next season’s projects. One project that always seems to be on that list is divid­ing peren­ni­als. It is a task that is easy to put off, per­haps because we are not quite sure when or how to do it.

Signs of a plant need­ing divi­sion are when it flow­ers less and the blos­soms are small­er, when its foliage is sparse and unhealthy, or when the cen­ter of the plant is unpro­duc­tive. Three major rea­sons to divide are to main­tain the size of a plant, to reju­ve­nate it, and to increase the num­ber of spec­i­mens. By divid­ing rapid­ly spread­ing peren­ni­als, they are kept at a man­age­able size before they out-com­pete oth­er plants. Divid­ing an old­er plant that has crowd­ed itself will reju­ve­nate it, result­ing in vig­or­ous growth. Divid­ing peren­ni­als is also an excel­lent way to cov­er more gar­den space at a min­i­mal cost.

Gen­er­al­ly it’s best to divide spring and sum­mer bloomers in the fall, and fall bloomers in the spring. This sched­ule allows the plant to be in stor­age mode” rather than in flow­er­ing” mode, so it can put its ener­gy into root and leaf devel­op­ment as it gets estab­lished. Fall divi­sions should take place 4 – 6 weeks before the ground freezes and be mulched to pro­tect the roots and pre­vent heav­ing. Spring divi­sions ide­al­ly take place just as the plant begins to grow. Divide ear­ly enough to allow time for roots to get estab­lished before hot weath­er. If tem­per­a­tures increase quick­ly, apply­ing a lay­er of mulch will help to keep the roots cool. Be aware that peren­ni­als divid­ed in the spring usu­al­ly bloom a lit­tle later.

Before divid­ing, give plants a good soak­ing the day before and choose a cool and cloudy day. It’s best to cut the stems and foliage back to about 6” to pre­vent loss of mois­ture. To reduce root dam­age use a spade and dig straight down about 5” away on all four sides before lift­ing the plant up. Once out split the plant into divi­sions by spade, fork, knife — or even ax! Some­times hos­ing the root mass can help you see what you are doing, but it does stress the root sys­tem. Each divi­sion should include 3 – 5 sec­tions, be they stems, fans, eyes, or rhi­zomes. As a rule, divid­ing every three to five years will help keep most plants hap­py and healthy.

Any extra divi­sions are espe­cial­ly wel­come at the Arboretum’s spring and fall plant sales. They also make great gifts to fel­low gar­den­ers. As Luther Bur­bank said, Flow­ers always make peo­ple bet­ter, hap­pi­er, and more help­ful; they are sun­shine, food and med­i­cine for the soul.”

Fall 2015

Volume 33 , Number 4

Share this

The Latest from Landis

Oct 07, 2023 | Nolan Marciniec

The Landis community mourns the loss of Anne Donnelly on October 4, 2023

Anne Donnelly was the first of the many friends I’ve made at the Arboretum and... read more

Oct 01, 2023 | Fred Breglia, Executive Director

From the Director’s Desk: Update on the Big Tree Search

Landis Arboretum has successfully kicked off its most recent Big Tree Search, and the tree... read more

Oct 01, 2023 | Erin McKenna Breglia

From the Garden: Your Autumn Garden Must Haves!

It’s certainly been a rainy summer, but the rain has helped keep our plants green... read more

Oct 01, 2023 | Nolan Marciniec

Landis Portraits: A Series About the People Behind the Plants at the Arboretum - Chuck Mueller

Chuck Mueller Volunteering, Chuck Mueller said, “is something you have to believe in . ... read more

Oct 01, 2023 | Nolan Marciniec

Volunteers Celebrate Meeting House Renovation

Shawn Bevins, Jim Paley, Craig Blevins, Fred Breglia, and Peter Bakal On a Sunday afternoon... read more

Oct 01, 2023 | Sam McClary

Apples and Man: A Book Review

Apples and Man, by Fred Lape “Apples and Man,” written by Arboretum founder Fred Lape... read more

News Archive