Dividing perennials is an important part of gardening. It allows the gardener to maintain their garden beds and remove plants that are dying or unproductive. Division of perennials is only a possible option if you have healthy plants with healthy root systems. Divided plants will need to be replanted to give them a chance of survival.
There are several reasons why perennials should be divided, but the most important one is that some perennials won't bloom if they are overcrowded. They need to be divided every few years to avoid overcrowding and avoid the plant being overworked. They will then grow bigger and produce more flowers.
Other reasons to divide your perennial include:
- Rejuvenate the plant and stimulate new growth
- Increase the number of plants
- Control the size of the plant
Fall blooming plants are divided in the spring. Perennials that bloom in spring and summer are divided in the fall because:
- You will have more time to do it as there is less gardening work in the fall compared to spring.
- It is easy to find the plant in your garden that needs to be divided
- When dividing your plants in the fall, make sure to do it four to six weeks before the ground freezes so the plants have time to establish. This is particularly important in colder climates.
Some perennials that do best being divided in the fall are:
- Bearded Iris
- Jack In The Pulpit
- Oriental Poppy
- Siberian Iris
The University of Minnesota Extension has put together a good list of perennials and what time of the year you should divide them. You can download the pdf here.
We are going to review how to divide three common groups of perennials based on their roots systems and how they grow:
Clumping – Perennials that fall under this group are Hosta, Daylilies, Gaura, and Astilbes. They grow from a central clump called a crown. The plant grows bigger each year and produces offsets. To divide the plant, dig up the entire plant making sure you are a good distance from the center, so you do not damage the roots. Once the plant is out of the ground shake off the dirt and loosen the roots and then look for places to divide the plant. Separate your pieces making sure each piece has roots and foliage. Plant the original plant back in the spot it was dug up and amend the soil to add nutrients. Plant the piece that was divided with amended soil. Then water the plants with a fertilizer.
Spreading – Plants in this group are Bee Balm and Perennial Vinca. These plants grow by surface or underground roots or stems or dropping their seeds. They even look like individual plants that have their own crown or root system. These plants are easy to divide. All you need to do is dig up the ones you want to move and plant them in a new spot. Leave the other plants alone.
Woody – Lavender, Rosemary, and Thyme are examples of plants in this group. The plant typically has one main stem or trunk. It spreads when one of the stems takes root. All you have to do is cut the stem between the main stem and the new one. Plant the new plant and you are done.
You might find when you have divided the plants it is wilting or seems to be in shock. This is normal, just keep watering and fertilizing it.