Why Dividing Perennials is Beneficial
Dividing is the process of lifting an established perennial out of the ground, loosening or cutting the root system, and creating more plants from one. While it may sound like plant abuse or a primitive form of cloning, it’s actually beneficial for both the plant and the gardener. Division helps control the plant’s size, rejuvenates its health, and provides bonus plants to expand your garden or share with friends.
When to Divide Perennials
Different perennials prefer to be divided at different times, but bloom times can serve as a helpful guide:
- Spring Bloomers: Divide in the fall.
- Fall Bloomers: Divide in the spring.
According to horticulturist Wendy Brister, early spring is often a safe time to divide most plants, as mild and moist conditions help roots grow before summer stress. Similarly, fall conditions can also work well if you divide at least four weeks before the first hard frost.
Plants That Don’t Like to Be Divided
Some perennials, particularly those with taproots, don’t divide well. Examples include:
- Baptisia australis (False Indigo): Prefers to stay put.
- Asclepias tuberosa (Butterfly Weed): Best propagated through seedlings.
Taprooted plants like poppies and thistle may struggle when moved but can still survive with proper care. Replant them carefully and water regularly until they re-establish.
Signs Your Perennials Need Dividing
Some plants thrive on division and may show signs when they need it. Watch for:
- Reduced blooming after a few years.
- Centers of clumps dying out, as seen in plants like Rudbeckia.
- Plants like daylilies that bloom less as the clump grows too large.
Regularly dividing perennials every two to three years keeps them healthy and encourages vibrant growth.
How to Divide Iris
Iris is a classic example of a plant that benefits from division. Here’s how to divide them:
- Divide Iris after they bloom in summer or early fall.
- Cut back the leaves to several inches tall.
- Lift the plant and use a sharp knife to separate new rhizomes from older ones.
- Discard old rhizomes and replant the smaller, newer ones shallowly in the soil.
Dividing Iris ensures they continue blooming year after year.
Final Tips for Dividing Perennials
Most perennials are resilient and can bounce back even if divided outside ideal conditions. Handle your plants confidently—they are tougher than they look! With regular care, your perennials will reward you with healthy growth and vibrant blooms.