Bee balm is a popular perennial plant with beautiful summer blooms that attract butterflies, bees, and hummingbirds. However knowing when to cut back bee balm can not only increase flowering, it also keeps the plants more compact and can reduce the occurrence of powdery mildew. In this article I’ll detail how and when to cut back the bee balm plants in your garden.

What is bee balm?

Also known as bergamot and Oswego tea, bee balm is an herbaceous plant native to North America and hardy in USDA zones 4 to 10. Monarda didyma is the most common cultivated species, but wild bergamot, Monarda fistulosa, is also popular. There are many cultivars of these two species available at garden centres as well as online nurseries.

Bee balms are members of the mint family and have the characteristic square stems and spreading habit. However, they are not as aggressive as mint and form large clumps in the garden. Bee balm grows best in full sun to partial shade and rich, lightly moist soils. They’re drought-tolerant, but more prone to foliar diseases when grown in very dry soils. Depending on the cultivar, they grow 1 to 4 feet tall and flower from mid to late summer. The fragrant foliage and spiky flower clusters in bright shades of red, purple, lavender, pink, and white have made this an essential plant for flowerbeds or a pollinator garden. 

Why it’s important to know when to cut back bee balm

There are a handful of reasons why knowing when to cut back bee balm is helpful. Here are my reasons for pruning this hardy perennial:

• It results in bushy, compact growth – Cutting back bee balm at the right time encourages stronger stems that don’t need to be staked or supported. This pruning technique is called the ‘Chelsea Chop’ and you’ll find more on it below.
• It delays flowering for a longer season of blooms – Cutting back some, but not all, of your bee balm plants gives you the longest possible show of flowers.
• It promotes heavier flowering – Deadheading regularly encourages the plants to keep pushing out new blooms.
• It can reduce the occurrence of powdery mildew – Powdery mildew is a fungal disease common on bee balm plants. It’s easy to spot as the leaves are coated in a grayish-white, powdery substance. It’s unattractive but also blocks sunlight from reaching the leaves. This results in early leaf drop and fewer flowers.

When to cut back bee balm: 4 easy options

Figuring out when to cut back bee balm depends on your goals. Are you trying to prevent powdery mildew? Do you want the flower show to extend for as long as possible? Would you like bushier, tidier plants? Here are 4 options for when to prune the plants. 

Option 1: Give the plants a ‘Chelsea Chop’ in spring

‘Chelsea Chop’ is a pruning technique that impacts plant height, stem flopping, and bloom time. It results in stocky stems and plants that don’t need to be staked or caged. It’s best done in late spring when the plants are 12 to 18 inches tall. Using hand pruners or hedge shears, cut bee balm plants back by one-third to one-half. 

I typically give half of my bee balm plants the ‘Chelsea Chop’. The non-pruned plants bloom at the normal time while the cut plants start to flower a week or two later. This gives me (and the bees!) the longest possible flowering season. 

Option 2: Thin the stems in spring

This is helpful if you find powdery mildew to be an annual issue. Thinning the stems in early spring ensures good air circulation and reduces humidity through the plant. This also allows more sun to reach the leaves which can reduce the occurrence of mildew. Using your hand pruners clip out about a quarter of the stems, cutting them back to ground level. 

To further decrease the risk of powdery mildew, plant resistant cultivars like Raspberry Wine, Marshall’s Delight, Purple Rooster, Jacob Cline, or Violet Queen. Also plant in full sun and space your plants 18 to 24 inches apart. 

Option 3: Deadhead spent flowers in mid to late summer

Cutting off bee balm flowers as they fade not only keeps the plant looking tidy, it also promotes new flower production and extends the blooming period. I use garden snips or hand pruners to clip the stems back to a healthy set of side shoots. These will push out new growth and fresh flower buds. These secondary flowers may be a bit smaller than the first flush, but will still delight the pollinators and hummingbirds. Aim to deadhead weekly. 

Option 4: Cut back bee balm stems in late summer or autumn

When the leaves fall in autumn, cut the plants back. If they had powdery mildew, take them all the way to the ground. If they were unaffected, either leave them so the birds can enjoy the seed heads or cut them back to a height of 8 to 10 inches. Leaving the stem stubs in the garden provides winter cover for insects. Come spring you can then clip back any remaining bee balm stems back to the ground to promote fresh new growth. 

I would also recommended raking up and removing any fallen bee balm leaves and debris to further reduce the risk of powdery mildew the following season. Don’t compost diseased foliage.

Bee balm growing tips

Besides knowing how and when to cut back bee balm, there are a few others tasks you can do to keep the plants looking their best. 

• Site selection – Boost plant health and minimize the occurrence of diseases by planting bee balm in the right site. It should offer full sun to part shade and average garden soil. Don’t plant bee balm in a spot where water doesn’t drain away quickly after a rain. I like to add a couple inches of compost to the planting hole as well as an organic flower fertilizer. 
• Cultivar selection – If you want low care bee balm plants, buying vigorous disease-resistant cultivars is essential. See above for suggestions.
• Watch for pests – While bee balm can be a target of aphids, thrips, and spider mites, they’re relatively unbothered by insects, deer, or rabbits. In rare cases you might spot stems wilting or breaking off and upon closer inspection find stalk borers. The adult is a moth which lays eggs on the stems in autumn. By spring the larva enter and tunnel up the stem causing wilting. Cut the plants back and burn the stems to eliminate the pests. 
• Water smart – I rarely water established bee balm plants, but I do occassionally deep water the first growing season. It’s best to direct moisture to the soil or mulch, not the plant itself, using a long-handled watering wand. This is because splashing water can spread disease spores. 
• Divide occasionally – With their spreading growth habit, bee balm plants eventually become overcrowded and start to die out in the center. Keep your clump healthy by digging up, dividing, and replanting the smaller pieces, every three to four years.

Final thoughts on when to cut back bee balm

A bee balm plant is a perfect partner for other low-care perennials like phlox, daylilies, coneflowers, and black-eyed Susans. They thrive in similar growing conditions and bloom around the same time. Knowing when to cut back the plants results in healthier, more vigorous growth as well as a later show of flowers. Plus, you can reduce the issues like powdery mildew. For more information on cutting back perennial plants, be sure to read these awesome articles: 

• When to cut back irises
• Learn the best timing for cutting back hostas
• The best time to clip back peonies
• When to cut back hydrangeas