How, when and why to divide garden perennials for better blooming

When spring and early-summer perennials start to overgrow their spaces, bloom less, produce smaller flowers or flop over with holes in their centers, they are signaling a need for division. This is their way of communicating that they require more room to thrive. To keep your garden healthy and vibrant, it's recommended to divide these plants every three to five years.

Dividing your perennials offers several benefits. It allows for the creation of free plants for your garden while preventing overcrowding, which can lead to competition for resources and increased susceptibility to mold and fungal diseases.

However, not all perennials benefit from division. Those with woody crowns or deep taproots, such as lavender, Russian sage, butterfly weed, and Baptisia, are better left undivided. As a general rule, it's best to divide late-summer and fall bloomers in the spring, once they have emerged from the ground, and spring and early-to-mid-summer bloomers in the fall.

This is because plants with established roots can better handle the stress of division during their dormant period. In colder climates, ensure that division is completed at least four to six weeks before the ground freezes to give the roots ample time to establish before entering dormancy.

To prepare for division, water your plants deeply a day or two before the task. Cut back the plants if necessary to expose their crowns, or the points where the top growth meets the roots. Using a garden fork, carefully lift the plant clump, taking care not to damage the root system. Gently separate the clump into sections, ensuring each piece has healthy roots and at least three strong shoots.

Immediately dig holes for the new plants, making them wider than the clump and deep enough to accommodate the root ball at or slightly above soil level. After planting, cover the soil with mulch to retain moisture, suppress weeds, and regulate soil temperature during winter. In the spring, your new, divided plants will flourish as healthier, more vigorous specimens with ample space to grow.