Shrub · Scrophulariaceae
Butterfly Bush
Buddleja davidii
Hand it full sun and a bold spring cut, and the butterfly bush fills up 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
Honestly, few shrubs draw in pollinators the way a butterfly bush does in full bloom. The long, tapering flower spikes open from summer into early fall and buzz with butterflies, bees, and hummingbirds going after the nectar. It grows fast and easy in full sun, takes dry spells in stride once its roots are settled, and barely asks anything of you.
Think of it as a big, sprawling shrub. Plants get up to 6 to 12 feet (1.8 to 3.7 m) tall and can spread even wider than that, with arching stems that bloom on the current season's growth. And that habit? It's the whole trick to growing it well: cut it back hard each spring and it pays you back with strong new shoots and the fullest flower show.
There's one real downside you'll want to know before you dig in. The common species seeds itself all over and has escaped from gardens to become a regulated noxious weed in states like Oregon and Washington. You can still grow it nicely, though, by going with a low-seed cultivar and clipping off the spent flowers before they get a chance to set seed.
Care
The short version: full sun and ordinary, well-drained soil, a deep drink only every once in a while once it's settled, a bold cut back in late winter, and some deadheading through summer to keep the flowers going and the seed under control.
Light
Butterfly bush really wants full sun, ideally 6 or more hours a day. It'll get by in part shade, but you won't love the result: leggy, thin growth and way fewer of the flower spikes that bring in the pollinators.
Water
Water new plants regularly through that first season so the roots can settle, then you can back off. Once it's established it's drought tolerant and only needs a moderate soak every 7 to 14 days. Keep the soil a touch dry rather than soggy, since wet feet are an open invitation to root rot.
Soil
It'll take just about any average, well-drained soil and handles a wide pH from 6.0 to 8.0. The one thing it really can't stand is poor drainage, so work some grit or compost into heavy clay before you plant.
Temperature
This is a tough, cold-hardy shrub that handles roughly -20°F to 100°F (-29°C to 38°C) across zones 5 to 9. At the colder end of that it often dies back to the ground each winter, then pops back up from the base come spring.
Humidity
Plain old outdoor air is all it asks for, so there's no humidity target to worry about. Good airflow matters way more than any number, since it helps keep mites and leaf problems from settling in.
Feeding
Keep it light. One feeding in spring is plenty, and too much fertilizer just pushes leaves instead of flowers. In halfway decent soil, it'll often be happy with nothing at all.
Pruning
Since it blooms on new wood, cut it back hard in late winter or early spring, down to about a foot off the ground, for the strongest growth and the biggest flowers. Then deadhead the spent spikes through summer to keep new blooms coming and stop the plant from seeding itself everywhere.
Repotting
Butterfly bush is a big shrub, so it rarely lives in a pot for long. If you do grow one in a container, repot only when the roots circle the pot, poke out of the drainage holes, or water runs straight through, all signs it's outgrown where it is.
Size & spacing
Give this shrub some real room. Plants get 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 space them well apart and keep them clear of paths and smaller plants they'd end up shading out.
When to plant
Butterfly bush sticks to a pretty simple yearly groove. Pop new plants in during spring once the frost is done, cut settled shrubs back hard before they start growing, and the flower spikes carry you right 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 healthy butterfly bush hardly causes any trouble, and what little it does usually comes down to wet feet, a dry spell, or a spring pruning you forgot. Match what you're seeing below to the cause and jump in before it knocks the plant back.
Wilting and dieback when the ground won't dry out
When soil stays wet, it sets up root rot, and that's why the top of the plant looks half-starved no matter how much you pour on. Start with the drainage and quit overwatering, then work in lots of grit if the bed runs to heavy clay. Out on sandy coastal soil, nematodes can leave the same mess behind, and a plant that's hit hard is usually better off pulled and replaced.
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, bronzed leaves with a thin webbing over them
So what's going on here? It's spider mites, and they tend to move in when a plant has gotten hot, thirsty, and stressed out. Hit the leaves with a strong blast of water to knock them loose, then keep the roots watered all through the dry weather. If a few stick around, dab some insecticidal soap or horticultural oil on the foliage.
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 flowering on long, leggy stems
When a butterfly bush barely flowers, it's usually begging for more sun or a real spring haircut. Find it a home with at least 6 hours of direct sun, then cut it back hard in late winter or early spring, because it blooms on new wood. Keep snipping off the faded spikes through summer and the fresh ones just keep coming.
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's the good news if you've got pets: the butterfly bush is not poisonous to cats, dogs, horses, or people, and it doesn't show up on the ASPCA toxic-plant lists at all. The real concern isn't toxicity, it's how invasive it is, since the common species spreads into the wild and counts as a regulated weed in some states. The sap can irritate skin too, so wear gloves when you prune.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
No need to worry if a nosy cat takes a bite, because butterfly bush isn't on the ASPCA toxic list. Sure, a huge mouthful of any plant can stir up a little drool or a queasy belly, but that sorts itself out soon enough.
Dogs Safe
Your dog can gnaw on the leaves and be totally fine, since the shrub carries nothing toxic for them. The one thing to keep an eye on is the same as with any plant, a mild tummy ache if a dog gobbles down a big helping.
Horses Safe
Nobody has recorded any toxicity in horses. They mostly skip the woody, bitter stems anyway and go graze somewhere tastier.
Rabbits Safe
A rabbit that nibbles a leaf or two will be perfectly okay, since there's no poison here for them. Just keep any green treat to a small bite so it doesn't edge out the hay and pellets.
Livestock Safe
Cattle, goats, and sheep can graze right next to a butterfly bush with no poisoning worries, and honestly the woody growth doesn't tempt them much to begin with.
Birds Safe
There's nothing toxic here for birds either. The nectar pulls in butterflies and hummingbirds, but it's the seed the plant scatters that carries it out into the wild where nobody wants it.
People Safe
No part of the butterfly bush is really poisonous to people, and there's nothing on it you'd want to eat anyway. The sap can bother sensitive skin, so grab a pair of gloves before you settle in for a heavy prune.
No special toxicity handling required; wear gloves if pruning to avoid skin irritation from sap.
Varieties
There are loads of butterfly bush cultivars out there, and the ones worth tracking down either show off a standout flower color or set so little seed they just stay put. Here are a few worth knowing by name.
Black Knight
A long-time favorite that folks keep coming back to for its deep, almost-black purple flower spikes.
Lo & Behold 'Blue Chip'
A tidy little dwarf that sets so few viable seeds it sails past Oregon's seedless butterfly bush rules.
Miss Molly
A hybrid cross with warm red-purple flowers, confirmed as non-davidii, which is how it slips out of Oregon's noxious weed regulation.
How to propagate
Butterfly bush makes more of itself easily, both from cuttings you take on purpose and from seed you'll usually want to stop.
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 your most reliable bet for making more butterfly bushes, and they hand you the exact same cultivar you started with. Take soft green tips in spring or early summer, or grab woody pieces while the plant is resting from late fall into early spring. Dip the cut end in rooting hormone, keep the soil moist, and softwood cuttings put down roots in about 2 to 5 weeks.
SeedEasy
Self-seeds readily in the garden · One growing season to a small plant
Leave the species to itself and it scatters seed everywhere, and a stray seed turns into a small plant inside one season. That's exactly the catch, though, because the wild species is invasive and regulated in parts of the country. Don't sow the straight species where it's a noxious weed, and deadhead so it can't seed itself out into the wild.
Myths
Butterfly bush is always a harmless choice for the butterfly garden.
Sure, the flowers feed grown butterflies, but the plant gives their caterpillars nowhere to live, so it only covers half of what they need. And here's the real problem: the common species seeds itself like crazy, with one flower cluster dropping over 40,000 seeds, and it has spread into the wild enough to be a regulated noxious weed in Oregon and Washington. So what helps? Plant a sterile or seedless cultivar, or a native nectar shrub, and deadhead the spent spikes so it can't seed itself all over the place.
Butterfly bush blooms on old wood, so you should never cut it back hard.
It's actually the other way around, because it flowers on new, current-season wood, which is why a hard cut does it a favor instead of any harm. Take it down close to the ground in late winter or early spring and you'll get strong fresh shoots and fuller flower spikes. And in the coldest zones it often dies back to the ground on its own anyway.