From A to Z: Dividing and Propagating Perennials

From A to Z: Dividing and Propagating Perennials

Rudbeckia or black-eyed Susan plants look ready to be divided. (Photo by Pam Baxter)

This summer, the rudbeckia (black-eyed Susan) really took off. After three years of steady but slow growth, the one plant I installed three years ago had spread to the point where it had not only outgrown its intended neighbors, but also appeared in another patch across the small garden path.

This encroachment and out-of-bounds explosion by rudbeckia is an example of one of the worst things and one of the best things I have learned about raising perennials. The worst part: Although perennials can be delightfully care-free, you never finish them; They will grow too large for the space. Best of all: You can get more perennials simply by dividing them and planting the “extras” elsewhere.

So, back to Rudbeckia, it’s clearly time to divide. But – is this really so? A gardening magazine article by Megan Chen that arrived in my email inbox a few weeks ago provides a simple rule for determining the best time to divide perennials, based on when they bloom.

First of all, the article points out that plant division is most successful when done in the spring or fall. This makes perfect sense. In the summer, plants may already be stressed by the heat. This is not the time to dig plants out of the soil, cut their roots, and then replant them in a new location. Winter is clearly not an option.

Since we work in either spring or fall, here’s the rule: “Perennials should be divided in the opposite season to the season they bloom – so late summer bloomers and fall bloomers should be divided in the spring, while spring and early summer” Bloomers will do better if they are divided in late Summer or early fall.

This gives summer bloomers all spring to put their energy into developing roots and leaves. Likewise, dividing spring bloomers and replanting them in the fall gives these plants a chance to recover and strengthen after the blooming season. This means I will have to wait until spring to divide the rudbeckia.

As someone who has spent most of my gardening life growing vegetables, I’m still learning about perennials. One point in the article that I wouldn’t necessarily have thought of is that it’s essential to make sure the new plants are large enough. “This is especially true in the fall,” she says, “when they have less time to establish before the growing season ends. A plant that may have made five small cuttings in the spring may instead have three larger cuttings in the fall.

Some additional things to note:

Space plants with plenty of room to grow until they reach mature size

– When replanting divided plant parts, place them in the ground at the same depth at which they were previously growing

-If it’s still sunny and hot in the fall, make a small “tent” to shade the plants in the middle of the day

– Treat transplants “like any new plant in the garden” and water them deeply to encourage root growth

Note: For the full article from Gardening Magazine, go to

Pam Baxter is an avid organic vegetable gardener – and budding permaculture farmer – living in Kimberton. Email directly to, or mail to PO Box 80, Kimberton, PA 19442. Pam’s Children’s Books – Big Life Lessons from Nature’s Little Secrets, and On Grandpa’s Beach in Maine – are available on Amazon, at /author/pamelabaxter.

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