By Juliet Blankespoor, Herbalist, Teacher, Gardener, Writer and Botanical Photographer
Following is adapted, with permission, from the Chestnut School of Herbal Medicine’s 1,000-hour Herbal Immersion Program. The program is the most comprehensive handcrafted online herbal course available. Learn more at Chestnut School of Herbal Medicine..
As a gardener, you’ve undoubtedly bought many plants to populate your garden, but you can’t beat the satisfaction of propagating your own. Dividing roots is perhaps the easiest and least expensive way to quickly fill your garden with mature plants. In a nutshell, this involves digging up a plant and separating a portion of the root system, and then replanting the separated portions, or divisions. The daughter plants, or divisions, may be planted directly in the garden or potted in preparation for moving to a new location. Depending on the plant, it’s possible to make more than 20 divisions from just one mother plant.
When you propagate a plant by root division, the new plant will be an exact clone of the parent. This is how we maintain a specific set of desired traits, such as height, flower color, flavor, aroma, or any number of distinct qualities that allow for that plant to stand out from the rest of its species.
Most herbs can be divided through root division, especially plants that run or clump. I don’t recommend dividing plants with taproots or a single stem, as they typically won’t “take.”
Early fall and early spring are the best times to divide roots because plants are more dormant. In the fall, just make sure to divide your roots before too many hard freezes, as the cold can stress your divisions. You’ll want to divide roots when the ground isn’t too wet, as the soil will be clumpy and adhere to the root system, making it challenging to get to the roots and see what’s going on.
To start, its best to gather a digging fork, pruners, flat-ended shovel, and a Japanese digging knife, or hori-hori. The digging fork is especially helpful, as the tines minimally disturb the soil. The blade of a Japanese digging knife has a sharp or serrated side to saw through difficult roots. Finally, some roots are just so tough that you’ll need to jump on a flat-ended shovel to sever them.
Step-by-Step Guide to Root Division
- Dig the plant. Choose a vigorous, large plant that can withstand some stress. Use a digging fork or shovel to loosen soil in a circle around the plant. Gently pry plant from soil, excavating side roots if needed.
- Remove excess soil. Shake away just enough soil to see what you’re working with. You may need to thump the root system in its hole to dislodge soil clumps. Be careful, as removing all the soil will damage the tender microscopic root hairs.
- Size up the root system. Determine how many buds or shoots the root system has and decide how many cuts to make, yielding a few large divisions or many small divisions. Each plant is truly unique in how small of a division will actually survive. Be certain to have at least one shoot or bud per division and a large enough root system to support it.
- Make divisions. Using one of the tools mentioned above, divide your roots. For roots that are growing loosely, pry apart divisions with your hands. Denser root systems may require sawing into segments with a hori-hori. And tough root systems require a shovel.
- Trim the tops. This is the most important step in successful root division. When you disturb the root system, the plant can no longer support the original aboveground vegetation. If the plant is dormant, you can skip this step. If your plant is an herbaceous perennial that is already dying back for the winter, you can completely cut back the aboveground growth. If the plant is actively growing with many stems, cut the stems back by half. If it just has emerging leaves, remove half the leaves. If you’re replanting the mother plant, make sure to cut back its growth as well.
- Transplant into the garden or pots. Transplant “divisionlings” into their forever home in the garden or pot them. Make sure to plant at the same soil depth they were originally growing. Potted divisions can be grown until their root system is established and has filled up the pot, and then they can be transplanted or shared with a friend.
- Water. Water your divisions with fresh water or prepare a solution from willow or seaweed that encourages rooting.
The Chestnut School of Herbal Medicine is located in the botanically rich Appalachian Mountains, outside of Asheville, NC. Their passion for healing plants, herbal education, and medicinal gardening is at the heart of all their teachings. Their online courses: the Herbal Medicine Making Course, the Herbal Immersion Program, and the Foraging Course (launching in early 2018).
Juliet Blankespoor is the botanical mastermind behind the Chestnut School of Herbal Medicine, which she founded in 2007 after deciding to become a professional plant-human matchmaker. She has more than 25 years of herbal experience.