Bee Balm

Bee balm is a North American native that produces shaggy, tubular flower heads in scarlet, pink, purple, or white — the kind of plant that stops hummingbirds mid-flight and draws bumblebees from across the yard. It grows in upright clumps, spreads steadily by rhizomes, and blooms reliably from midsummer into early fall. But it has one persistent problem: powdery mildew, a fungal disease that coats the leaves in a white-gray film and can defoliate an entire planting by August if conditions favor it.

The mildew shows up when the air is humid but the leaves stay dry — typically after a stretch of warm, still nights. Lower leaves develop white patches first, then the whole plant turns gray and unsightly. It does not usually kill the plant, but it ruins the look of the border and weakens the clump over time. The most effective defense is to choose a mildew-resistant cultivar in the first place — varieties like Jacob Cline or Marshall's Delight were bred specifically to resist the disease and can stay green all season in gardens where older types would be covered by July.

Spacing matters nearly as much as variety. Bee balm planted too close together creates the damp, still air that mildew thrives in. Eighteen inches between plants is the listed minimum, but two feet is better if you have the room. Thin the clumps in spring if they start to crowd — the goal is airflow through the foliage, not a solid wall of stems.

Consistent moisture helps reduce mildew stress, but standing water invites crown rot. Bee balm wants soil that stays evenly moist through the summer — not soggy, not bone-dry. Mulch around the base to hold moisture and water at the soil line rather than overhead. If mildew does take hold despite your precautions, cut the affected stems to the ground; the plant will often send up fresh growth that may bloom again in fall.

Bee balm spreads by underground rhizomes and can become aggressive in rich soil with ample water. Dig and divide clumps every two to three years, both to control the spread and to rejuvenate the center of the clump, which tends to die out as the plant ages. The divisions transplant readily in spring or fall.

Most cultivars bloom in their second year from seed or transplant. Deadheading spent flowers can extend the bloom period, but the seed heads left standing attract goldfinches in late summer and add winter interest. If you are planting bee balm in a naturalistic meadow or cottage garden, its tendency to spread can be an asset rather than a problem — it fills gaps and holds its own against aggressive neighbors.