Bicolor Butterfly Bush Blooms: Colors, Timing and Season
We're deep into late September, and if you planted a Bicolor Butterfly Bush this spring or last year, it's probably still covered in flowers right now. Your neighbors with solid-color butterfly bushes may already be winding down, but the bicolor form keeps surprising growers with its willingness to rebloom through October if you give it the right attention. This guide covers what makes bicolor flowers different, when to expect them, and how to stretch the show through fall.
What Bicolor Butterfly Bush Flowers Actually Look Like
The Bicolor Butterfly Bush produces flower spikes with a distinctive two-tone mix of pink (or rose) paired with purple or lavender. The exact shade combination varies by grower, since the bicolor form sold in most nurseries is often a generic trade strain rather than one fixed cultivar, so don't assume all bicolor plants look identical. Some lean more rose and lilac, others more coral and deep purple. What they all share is that fragrance: a sweet, honey-like scent that's strongest on warm, still days. If you brush past the plant on a humid morning, you'll catch it. If there's a breeze, the scent travels.
The flowers grow on narrow, upright spikes that can reach 8 to 12 inches long. Behind those spikes are lance-shaped, gray-green leaves with a slightly silvery, felted underside. This soft foliage texture is part of why the plant photographs so well; the flowers seem to emerge from a silvery cloud.
When Does Butterfly Bush Bloom: The Full Season
Bicolor Butterfly Bush blooms roughly from June through September or October, depending on your zone and how you prune. In zones 7-9, where the plant grows as a fully woody shrub, you'll see flowers from early summer through the first frost. In zones 5-6, where the plant dies back to the ground each winter and regrows as a woody-based perennial, the bloom window is compressed into a shorter, more intense peak.
Early Summer (June-July)
The first flowers appear on new growth in early June in most regions. If you cut your plant back hard in late winter to about 12 to 18 inches from the ground, the new shoots that emerge in spring will flower by June. This is intentional: butterfly bushes flower on new wood, not old wood, so spring pruning is essential. The early blooms are usually the most abundant and the most vivid in color.
Mid to Late Summer (July-August)
By July, the plant is in full flower. Growth is rapid (established plants typically add 2 to 3 feet per year), so even plants pruned late may still flower. This is when deadheading matters most. If you let spent flowers fade and set seed, the plant sends energy into seed production rather than new blooms. Snipping off faded spikes every 5 to 7 days redirects that energy and encourages rebloom.
Fall (September-October)
This is where the bicolor form earns its keep. With consistent deadheading through summer, most plants will still be flowering in late September and into October. The flowers may come in smaller, lighter flushes than midsummer, but they're there. In warmer zones, you might get blooms right up to the first hard freeze.
Why Bloom Time Varies by Zone
In zones 7-9, the Bicolor Butterfly Bush is a woody shrub that survives winter. The woody framework stays in the ground, and pruning in late winter removes the previous year's growth. New shoots emerge and flower the same season.
In zones 5-6, the plant dies back to the ground each winter and regrows from the rootstock as a woody-based perennial. This means the plant starts from lower energy in spring, takes a few extra weeks to build enough growth to flower, and the bloom season is tighter. You may not see flowers until mid-June, and the plant may stop blooming earlier in fall.
Regardless of zone, the farther north you are, the shorter the warm season, and the narrower the window for reliable bloom. A zone 5 gardener usually sees reliable flowers July through early September. A zone 8 gardener might have color May through November (though this particular plant doesn't typically start quite that early).
The Role of Deadheading in Extending Blooms
Deadheading spent spikes through summer is not optional if you want fall flowers. Here's why: the plant's biological goal is to make seeds. Once a flower spike has ripened and dried, it has accomplished its goal. The plant can then slow flowering and focus on ripening more seed. If you remove spent spikes before they set seed, the plant keeps trying to reproduce and produces more flowers to make seeds.
To deadhead, simply pinch or cut off the faded spike just below where the flowers have dried. You'll see new flower buds forming along the stem, or the plant will flush new growth that flowers. Deadheading takes 10-15 minutes per plant if you do it weekly. If you skip it for 3-4 weeks, the flowers become fewer and smaller. If you never deadhead, you'll still get flowers, but far fewer than the plant is capable of producing.
Some gardeners prefer to skip deadheading in late August or September to allow the plant to set seed naturally and wind down for winter. That's fine. It's a choice, not a requirement. But if you want continuous fall color, deadheading through September is the most effective tactic.
Seasonal Tips for Right Now (Late September)
Extend the Show This Fall
If your Bicolor Butterfly Bush is still in flower now, keep deadheading. You've done the work all summer; finish strong. Remove any spent spikes and you should see new buds within 5-7 days. Even if the flowers are smaller or fewer than they were in July, they're still worth having.
Don't Prune Now
Resist the urge to cut back the plant before winter. Late-summer or fall pruning sends new growth that won't have time to harden off before frost. In zones 5-6, this new growth will be killed anyway. In zones 7-9, it can reduce hardiness. Wait until late winter, when the plant is fully dormant and buds are about to break. Then cut it back hard to 12-18 inches or a low framework of woody stems.
Water if It's Dry
If September or early October has been dry where you are, water your butterfly bush if the soil is dry 2 inches down. The plant is drought-tolerant once established (typically after the first full growing season), but it still benefits from water during bloom. Flowering takes energy and water.
Note the Peak Colors for Next Year
Pay attention to which weeks had the most or best flowers this year. In your zone, that's roughly when you can expect peak bloom again next year. Take a photo so you remember the flower color and how it paired with anything planted nearby. This information helps with garden design.
Planning Peak Blooms for Next Year
The most common reason for reduced flowering is skipping the spring pruning or cutting the plant back too lightly. The plant gets leggy (tall and sparse) and produces flowers only at the branch tips. To guarantee abundant flowers in 2027, mark your calendar now for late February or very early March (zones 7-9) or early April (zones 5-6). Cut the plant back hard to about 12 to 18 inches from the ground or to a low framework of woody stems. This triggers vigorous new growth that will flower heavily.
The second most common reason for reduced flowers is light. Butterfly bushes need full sun, which means at least 6 hours of direct sunlight. In part shade, blooms decline noticeably and the plant may become leggy. If your plant is in shade and flowering poorly, plan to move it or thin nearby trees or shrubs to let more light in.
Third, avoid over-fertilizing. Light annual feeding with a balanced fertilizer in spring is sufficient. Too much nitrogen promotes leggy growth and fewer blooms. If you haven't fertilized this year, you don't need to now. If you did fertilize in spring, you're done.
Bicolor Blooms vs. Other Butterfly Bush Colors
The solid-color cultivars like Black Knight (deep purple), Pink Delight (bright pink), and Royal Red (crimson) follow the same bloom timeline as the bicolor. However, gardeners often report that the bicolor form feels more generous with rebloom, especially in fall. This might be a matter of observation bias (bicolor flowers look lighter and more visible against green foliage, so you notice them more), or it might be a real trait of the strain. Either way, the bicolor is a reliable bloomer if you deadhead and prune correctly.
Connecting Bloom Timing to Your Growing Guide
For a complete picture of how to grow your Bicolor Butterfly Bush through the entire year, including detailed pruning, soil, watering, and pest management, see our Bicolor Butterfly Bush Care: A Complete Growing Guide. That resource covers everything beyond bloom timing.
Quick Reference: Bloom Timeline and Deadheading Checklist
| Time Period | What to Expect | Care Task |
|---|---|---|
| Late Winter (Feb-Mar in zones 7-9; Apr in zones 5-6) | Plant is dormant; buds are breaking | Cut back hard to 12-18 in. from ground |
| Spring (Apr-May) | Vigorous new growth; no flowers yet | Light annual fertilizing; ensure full sun |
| Early Summer (June) | First flowers on new growth; colors vivid | Begin deadheading spent spikes |
| Mid Summer (July-Aug) | Peak bloom; flowers abundant and large | Deadhead weekly; water if dry |
| Early Fall (Sep) | Blooms continue but lighter; may slow | Continue deadheading for rebloom |
| Late Fall (Oct) | Flowers fade or stop with first frost | Stop deadheading; allow plant to set seed |
| Winter (Nov-Jan) | Plant dormant; foliage drops or blackens | No action needed; plan spring pruning |
Deadheading Checklist (Summer-Early Fall)
- Inspect the plant weekly, or at least every 10 days
- Pinch or cut off any spike that has dried or faded
- Leave spikes that still have open flowers
- If reblooming slows, check that the plant gets at least 6 hours of sun
- Stop deadheading in late September to allow the plant to go dormant naturally
- Don't cut back the plant in fall; wait until late winter