Shrub · Scrophulariaceae
Butterfly Bush
Buddleja davidii
Give it full sun and a brave spring trim, and the butterfly bush rewards you with flowers and fluttering wings all summer.
Full sun
Every 7–14 days
USDA 5–9
6–12 ft · 1.8–3.7 m
Overview
Few shrubs make a beginner look so good as a butterfly bush in full bloom. The long, tapering flower spikes open from summer into early fall and fill with butterflies, bees, and hummingbirds chasing the nectar. It grows fast and forgiving in full sun, copes with dry spells once its roots settle in, and asks almost nothing of you in return.
Picture a big, easygoing shrub. Plants climb to 6 to 12 feet (1.8 to 3.7 m) tall and often spread wider still, their arching stems flowering on the current season's growth. That habit is the kindest part of the deal, because a hard cut each spring brings strong new shoots and the biggest, fullest flowers, and any clumsy cut grows right back.
There is one honest catch worth knowing before you plant. The common species seeds itself freely and has slipped out of gardens to become a regulated noxious weed in states like Oregon and Washington. You can still grow it happily by picking a low-seed cultivar and clipping off the faded flowers before they ever set seed.
Care
The short version: full sun and ordinary, well-drained soil, a deep drink only now and then once it has settled, a confident hard cut in late winter, and a little deadheading through summer to keep the flowers coming and the seed in check.
Light
Butterfly bush is happiest in full sun, ideally 6 or more hours a day. It will soldier on in part shade, but the reward is slim, with leggy, sparse growth and far fewer of the flower spikes that pull in the pollinators.
Water
Give new plants steady water through that first season so the roots can settle, then you can ease right off. Once it is established it turns drought tolerant and wants only a moderate soak every 7 to 14 days. Keep the soil on the dry side rather than soggy, because wet feet invite root rot.
Soil
It is forgiving about almost any average, well-drained soil and copes with a broad pH from 6.0 to 8.0. The single thing it won't tolerate is poor drainage, so dig grit or compost into heavy clay before you plant and it will thank you.
Temperature
This is a tough, cold-hardy shrub that takes roughly -20°F to 100°F (-29°C to 38°C) across zones 5 to 9. Toward the colder end it often dies back to the ground each winter, then springs up cheerfully from the base when warmth returns.
Humidity
Plain outdoor air suits it just fine, so there's no humidity number to chase. Good airflow helps far more than any reading, keeping mites and leaf troubles from gaining a foothold.
Feeding
Go easy here. One feeding in spring is all it needs, and too much fertilizer pushes leaves at the cost of flowers. In decent soil it will often be perfectly content with nothing.
Pruning
Since it flowers on new wood, cut it back hard in late winter or early spring, down to about a foot from the ground, for the strongest growth and the biggest blooms. After that, snip off the spent spikes through summer to keep fresh flowers coming and to stop the plant seeding itself around.
Repotting
Butterfly bush is a large shrub and rarely stays in a pot for long. If you do grow one in a container, repot only when roots circle the pot, push out of the drainage holes, or water runs straight through, all gentle signs it has outgrown its home.
Size & spacing
Give this shrub plenty of elbow room. Plants reach 6 to 12 feet (1.8 to 3.7 m) tall and spread 4 to 15 feet (1.2 to 4.5 m) wide, so set them well apart and clear of paths and smaller plants they would shade out.
When to plant
Butterfly bush keeps to a gentle, year-by-year rhythm that is easy to follow. Tuck new plants in during spring once frost has gone, cut settled shrubs back hard before they wake up, and the flower spikes carry you from summer into early fall.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Late winter to early spring (8-10 weeks before last frost) if growing sterile-permitting seed; species seeding is discouraged where invasive.
- Plant: Spring after last frost
- Harvest: Summer through early fall (June to September)
Hardiness
USDA hardiness zones: 5–9
Temperature: down to -29°C
Troubleshooting
A happy butterfly bush gives you very little grief, and the few troubles it does meet usually trace back to wet feet, a dry spell, or a missed spring trim. Match what you see below to its cause, step in early, and the plant bounces back without fuss.
Drooping and dieback where the soil stays wet
Don't worry, this one is fixable: ground that stays soggy invites root rot, and that is why the top looks starved even as you keep watering. Sort the drainage out, hold back on the water, and work plenty of grit into the bed if it leans toward heavy clay. On sandy coastal soil nematodes can cause the same look, and a plant hit hard is kindest to lift and replace.
Fix:
- Improve drainage and stop overwatering
- Plant in well-drained soil; amend heavy clay before planting
- Remove and replace severely affected plants in infested ground
Speckled leaves and a haze of fine webbing
If you spot this, take heart, because it is just spider mites, and they show up when a plant has been hot, thirsty, and stressed. A firm rinse from the hose washes most of them away, and keeping the roots watered through the dry weather does the rest. Should a few hold on, a little insecticidal soap or horticultural oil on the leaves clears them up.
Fix:
- Spray foliage with a strong jet of water to dislodge mites
- Keep plants adequately watered to reduce drought stress
- Apply insecticidal soap or horticultural oil to affected foliage if needed
Thin blooms on long, reaching stems
A shy bloomer is almost always asking for more light or a proper spring trim, and both are easy gifts to give. Settle it somewhere with at least 6 hours of direct sun, then cut it back hard in late winter or early spring, because the flowers form on new wood. Snip off the faded spikes through summer and fresh ones keep arriving.
Fix:
- Move or site in full sun
- Cut back hard in late winter or early spring since it blooms on new wood
- Deadhead spent spikes to encourage continued bloom
Toxicity
Here is reassuring news for a worried pet owner: butterfly bush is not poisonous to cats, dogs, horses, or people, and it never appears on the ASPCA toxic-plant lists. The thing to mind isn't poison but spread, since the common species escapes into the wild and counts as a regulated weed in some states. The sap can nip sensitive skin, so pop on gloves when you prune.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
You can relax around a curious cat here, since butterfly bush isn't on the ASPCA toxic list and a nibbled leaf does no harm. A really big mouthful of any plant might bring a bit of drooling or a queasy tummy, but that settles by itself.
Dogs Safe
A dog can chew the leaves without coming to any harm, because the shrub holds no toxin that affects them. The only thing to watch is the ordinary one with any plant, a mild upset stomach if a dog gulps down a large helping.
Horses Safe
Horses have nothing to fear from this plant, with no toxicity on record. They usually pass over the woody, bitter stems and graze happily elsewhere.
Rabbits Safe
A rabbit that tries a few leaves will be just fine, as there is no poison here for them. Keep any green nibble small so it doesn't push out the hay and pellets that matter most.
Livestock Safe
Cattle, goats, and sheep can graze beside a butterfly bush with no risk of poisoning, and the woody growth seldom appeals to them anyway.
Birds Safe
Birds are in no danger from the plant at all. Its nectar welcomes butterflies and hummingbirds, though the seed it drops is the part that carries it into the wild where it isn't welcome.
People Safe
No part of butterfly bush is truly poisonous to people, and there's nothing here meant for eating either. The sap can leave sensitive skin a little irritated, so slip on gloves before a serious pruning session.
No special toxicity handling required; wear gloves if pruning to avoid skin irritation from sap.
Varieties
Plenty of butterfly bush cultivars are out there, and the ones worth hunting down either offer a knockout flower color or set so little seed that they stay put. Here are a few friendly names to remember.
Black Knight
A much-loved old favorite, treasured for flower spikes so deep a purple they look almost black.
Lo & Behold 'Blue Chip'
A neat, compact little plant that makes so little viable seed it meets Oregon's seedless butterfly bush rules with room to spare.
Miss Molly
A cross-bred beauty with warm red-purple blooms, confirmed as non-davidii and so free of Oregon's noxious weed regulation.
How to propagate
Butterfly bush makes more of itself with very little effort, both from cuttings you take on purpose and from seed you will usually want to head off.
Stem cuttingsEasy
Softwood cuttings in spring to early summer; hardwood cuttings during dormancy in late fall through early spring · Softwood cuttings root in about 2-5 weeks
Cuttings are the kind, reliable way to make more of a butterfly bush, and you get the very same cultivar you started with. Snip soft green tips in spring or early summer, or woody pieces while the plant rests from late fall into early spring. Dip the cut end in rooting hormone, keep the soil gently moist, and softwood cuttings take root in about 2 to 5 weeks.
SeedEasy
Self-seeds readily in the garden · One growing season to a small plant
Left alone the species sows itself far and wide, and a stray seed grows into a small plant in just one season. That very ease is the trouble, since the wild species is invasive and regulated in parts of the country. Please don't sow the straight species where it counts as a noxious weed, and deadhead so it can't seed itself into the wild.
Myths
Butterfly bush is always a harmless choice for the butterfly garden.
Its flowers do feed grown butterflies, yet the plant gives their caterpillars nowhere to live, so it carries only half of their life. The bigger snag is seeding, with one flower cluster scattering over 40,000 seeds, enough that it has slipped into the wild and become a regulated noxious weed in Oregon and Washington. The happy fix is simple: choose a sterile or seedless cultivar, or a native nectar shrub, and snip off the spent spikes so it can't spread itself around.
Butterfly bush blooms on old wood, so you should never cut it back hard.
Quite the opposite is true, because it flowers on new, current-season wood, so a bold cut helps it rather than setting it back. Take it down close to the ground in late winter or early spring and it rewards you with strong fresh shoots and fuller flower spikes. In the coldest zones it often dies back to the ground by itself anyway, so there is little to fear.