Bicolor Butterfly Bush Blooms: Colors, Timing and Season

A common mistake people make with Bicolor Butterfly Bush is treating the first flush of flowers as the whole show. The spikes fade in August, the plant looks tired, and the pruners come out, or nobody touches it at all. Then the shrub sits through the best fall weather with no color. Handled right, it keeps opening flowers into October, and the honey scent hangs around with it.

This article talks about bicolor flower color, bloom timing by zone and the deadheading that keeps new spikes coming, and answers the questions customers ask us most. Read on to learn what to expect each month, what to do this month, and how to set up next summer's flowers before the leaves drop.

Why Your Bicolor Butterfly Bush Stops Blooming Early

One of the most common questions we get is why a butterfly bush that looked wonderful in July is bare by late August. Nine times out of ten, the spent spikes were left on the plant.

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.

You can stop deadheading once flowering winds down, and that's fine. It's a choice, not a requirement. But if you want continuous fall color, keep at it until frost ends the show.

When Bicolor Butterfly Bush Blooms: The Full Season

Expect flowers from June to September in most regions, with a longer tail where fall stays mild. Here is how the season unfolds.

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, so even plants pruned a bit 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

Bicolor Butterfly Bush is winter hardy in USDA zones 5 through 9, but it behaves differently at the cold and warm ends of that range.

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. In zone 5 you can usually count on flowers from July through early September. In zone 8 the show often runs from early summer well into late fall.

What Bicolor Flowers Look and Smell Like

Each flower spike carries a two-tone mix, usually purple or lavender paired with a warmer rose or burgundy tone. The exact blend varies from plant to plant, since the bicolor form sold in most nurseries is often a trade strain rather than one fixed cultivar. For comparison, the species is lilac with an orange throat, while a cultivar like 'Attraction' is listed as purple/lavender and red/burgundy.

What bicolor plants share is the 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. Behind them 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, since the flowers seem to emerge from a silvery cloud. It's also why the spikes draw so many visitors, as we cover in our guide to butterflies, bees and birds on this plant.

How Bicolor Compares With Solid-Color Butterfly Bushes

If you're choosing between a two-tone plant and a single color, the timing matters as much as the look.

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.

Customers often tell us the bicolor feels more generous with rebloom, especially in fall. This might be observation bias, since the lighter two-tone spikes are more visible against green foliage and you notice them more. It might also be a real trait of the strain. Either way, the bicolor is a reliable bloomer if you deadhead and prune correctly.

Seasonal Tips for Right Now (October)

In our rows, October is about finishing the flower season well and not starting new work. These are the four jobs we tell customers to handle this month.

Extend the Show This Fall

If your Bicolor Butterfly Bush is still in flower now, keep deadheading. You've done the work all summer, so 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

You'll read advice to tidy butterfly bushes in fall so the stems don't whip around in winter wind. We don't follow it, and here is why.

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

Because the flowers are borne on new growth, what you do between now and spring decides how much bloom you get. We often see the same three causes of weak flowering, and you can fix all of them before next season. Our guide to when and how to prune a Bicolor Butterfly Bush goes deeper on the first one.

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.

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

This table shows what the plant is doing at each point in the year and the one job that goes with it.

Time Period	What to Expect	Care Task
Late Winter (Feb-Mar in zones 7-9, Apr in zones 5-6)	Plant is dormant and buds are breaking	Cut back hard to 12-18 in. from ground
Spring (Apr-May)	Vigorous new growth, no flowers yet	Light annual fertilizing and full sun
Early Summer (June)	First flowers on new growth, colors vivid	Begin deadheading spent spikes
Mid Summer (July-Aug)	Peak bloom with abundant, large flowers	Deadhead weekly and water if dry
Early Fall (Sep)	Blooms continue but lighter, and may slow	Continue deadheading for rebloom
Late Fall (Oct)	Flowers fade or stop with first frost	Stop deadheading once flowering ends and let the plant wind down
Winter (Nov-Jan)	Plant dormant, foliage drops or blackens	No action needed, plan spring pruning

Deadheading Checklist (Summer-Early Fall)

Print this list or keep it on your phone. It covers the weekly routine from the first flowers until frost.

• 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 when frost ends the flowering, so the plant can go dormant naturally
• Don't cut back the plant in fall, and wait until late winter

Keeping Bicolor Color Going Until Frost

Bicolor Butterfly Bush rewards steady attention more than heavy work. Deadhead weekly while spikes are still opening, leave the plant unpruned this fall, and cut it hard in late winter. Do that and you get honey-scented, two-tone flowers from June until frost.

Customers come back to us for this plant because the flowers keep coming after other shrubs have gone quiet, and because the butterflies show up right on schedule. We grow it on our own farms and sell only top-quality plants.