If you grow bearded irises in Calgary, it’s important to divide them every few years to keep them healthy and blooming well. Here’s a simple guide to doing it right:
When to Divide
- Late July to early August is the best time to divide your irises. At this point, they’re dormant, so they can recover quickly.
- Avoid dividing later in fall, as the rhizomes won’t have enough time to grow roots before winter.
Why Divide?
- After 4-5 years, iris clumps get crowded and produce fewer flowers.
- Dividing creates healthier plants and more blooms.
- Plus, it’s a great way to share plants with friends or expand your garden.
Step-by-Step Guide
- Pick a healthy clump that’s crowded and has old, woody rhizomes. Remove it from the ground with a garden fork.
- Gently shake off the soil to see the rhizomes. Discard the old, woody center.
- Divide the rhizomes by pulling apart the clump with your hands or a sharp tool. Remove any damaged or soft sections.
- Trim the leaves to about 6 inches (15 cm) to make the plants easier to handle and prevent disease.
- Cut the roots to about 2 inches (5 cm).
- Plant the divisions about 12 inches apart, just shallow enough so the top of the rhizome is barely visible above the soil.
- Water well after planting, and keep the soil moist but not soggy.
Tips for Success
- Don’t plant the rhizomes too deep — this can delay blooming or cause rot.
- Keep the area weed-free to prevent pests.
- Watch out for iris borers, which can damage plants; remove debris in spring and fall, and consider spraying if infestations are heavy.
Final Note
Bearded irises might bloom fewer times the first year after dividing, but they’ll be full of flowers the next season. With a little effort now, you’ll enjoy a more vibrant, long-lasting garden in Calgary’s short growing season.
