Shrub · Scrophulariaceae
Butterfly Bush
Buddleja davidii
Give it full sun and a hard spring cut, and the butterfly bush turns a summer border into a haven of flowers and wings.
Full sun
Every 7–14 days
USDA 5–9
6–12 ft · 1.8–3.7 m
Overview
Few shrubs set a summer scene the way a butterfly bush in bloom does. Its long, tapering spikes open from summer into early fall and become a gathering place for butterflies, bees, and hummingbirds drawn to the nectar, a living centerpiece for the back of a sunny border. It grows fast and easy in full sun, takes dry spells in stride once rooted, and asks little upkeep in return.
Plan for a generous, loose-limbed shrub when you place it. Plants reach 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 secret to keeping the look sharp: a hard cut each spring brings strong new shoots and the fullest flower display, season after season.
There is one honest consideration to weigh before the spade goes in. The common species seeds itself with abandon and has slipped beyond garden walls to become a regulated noxious weed in states such as Oregon and Washington. You can still feature it beautifully by choosing a low-seed cultivar and clipping the faded flowers before they ever set seed.
Care
The short version: full sun and average, well-drained soil, a deep watering only now and again once it has settled in, a hard cut back in late winter, and steady deadheading through summer to keep the flowers coming and the seed in check.
Light
Butterfly bush belongs in full sun, ideally 6 or more hours a day, where it earns its place at the heart of a border. Part shade will keep it alive, but the result disappoints: leggy, sparse growth and far fewer of the flower spikes that bring in the pollinators.
Water
Water new plants regularly through their first season to settle the roots, then ease right off. Once established it is drought tolerant and asks only a moderate soak every 7 to 14 days, which makes it a forgiving choice for a low-fuss garden. Keep the soil on the dry side rather than soggy, since wet feet invite root rot.
Soil
It accepts almost any average, well-drained soil and tolerates a broad pH from 6.0 to 8.0, so it slots easily into most beds. The one thing it won't forgive is poor drainage, so work grit or compost into heavy clay before planting.
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, an easy fit for most climates. Toward the colder end it often dies back to the ground each winter, then resprouts from the base come spring.
Humidity
Ordinary outdoor air suits it perfectly, so there's no humidity target to manage. Good airflow matters more than any reading, helping keep mites and leaf troubles from taking hold.
Feeding
Keep it light. A single feeding in spring is plenty, and too much fertilizer pushes leafy growth at the expense of flowers. In a decent bed it often needs nothing at all.
Pruning
Because it blooms on new wood, cut it back hard in late winter or early spring, to within about a foot of the ground, for the strongest growth and the biggest flowers. Then deadhead the spent spikes through summer to keep fresh blooms arriving and to stop the plant seeding itself around.
Repotting
Butterfly bush is a large shrub that 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 signs it has outgrown its place.
Size & spacing
Give this shrub real room to settle into the design. 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 simple yearly rhythm that suits an easygoing garden routine. Set new plants out in spring once frost has passed, cut established shrubs back hard before growth begins, and the flower spikes carry the border 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 well-placed butterfly bush gives little trouble, and what does arise usually comes down to wet feet, a dry spell, or a skipped spring cut. Match what you see below to its cause and act early, before the look of the planting suffers.
Slumping and dieback in a bed that holds water
A spot that stays waterlogged sets the stage for root rot, and that is why the canopy looks famished even as the watering can keeps coming. Put the drainage right and pull back on water first, then fold a generous helping of grit into the bed wherever it runs to heavy clay. Along sandy coastal sites nematodes can leave the same mark, and a plant past saving is best lifted out 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 foliage veiled in fine webbing
The culprit here is spider mites, and they tend to move in when a border has been hot, parched, and short on water for a stretch. A firm pass with the hose sweeps most of them off, and steady watering through the dry weeks keeps the shrub from inviting more. For the stubborn few, a light coat of insecticidal soap or horticultural oil on the leaves finishes the job.
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 tall, reaching stems
When the display falls flat, the shrub is usually craving more light or carrying too much old growth. Find it a position with at least 6 hours of direct sun, then cut it back hard in late winter or early spring, since the blooms arrive on new wood. Clipping the faded spikes through summer keeps a fresh wave of flowers on the way.
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
Reassuring news for a household with pets: butterfly bush is not poisonous to cats, dogs, horses, or people, and it stays off the ASPCA toxic-plant lists. The real consideration is invasiveness rather than toxicity, since the common species escapes into the wild and counts as a regulated weed in some states. The sap can irritate skin, so wear gloves when you prune.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
A household cat can share the garden with this shrub at ease, as butterfly bush sits nowhere on the ASPCA toxic list and a nibbled leaf does nothing. Should a cat work through a large mouthful of any plant, a touch of drooling or a queasy stomach may follow, and it clears on its own.
Dogs Safe
The family dog can mouth the leaves with no cause for concern, since the shrub holds no toxin that troubles them. The only thing worth a glance is the everyday one with any plant, a mild upset stomach when a dog bolts down a large helping.
Horses Safe
Horses have nothing to worry about, with no toxicity on record. They generally pass over the woody, bitter stems and graze contentedly somewhere else.
Rabbits Safe
A rabbit that tastes a leaf will come away fine, as the plant carries no poison for them. Keep any leafy treat modest so it never crowds out the hay and pellets that anchor the diet.
Livestock Safe
Cattle, goats, and sheep can graze around a butterfly bush with no poisoning risk, and its woody growth rarely catches their interest to begin with.
Birds Safe
Birds face no toxic risk from the plant. Its nectar invites butterflies and hummingbirds to the garden, while the seed it casts off is the part that carries it into wild places where it isn't welcome.
People Safe
No part of butterfly bush is meaningfully poisonous to people, and it offers no edible crop to harvest either. The sap can irritate sensitive skin, so reach for gloves before settling in to a thorough pruning.
No special toxicity handling required; wear gloves if pruning to avoid skin irritation from sap.
Varieties
Butterfly bush comes in many cultivars, and the ones worth seeking out either bring a striking flower color to a planting or set so little seed that they behave themselves. A few are worth knowing by name.
Black Knight
A long-standing garden favorite, valued for flower spikes in a purple so dark they read as nearly black.
Lo & Behold 'Blue Chip'
A tidy, compact selection that produces so little viable seed it satisfies Oregon's seedless butterfly bush rules.
Miss Molly
An interspecific hybrid in warm red-purple, confirmed as non-davidii and therefore exempt from Oregon's noxious weed regulation.
How to propagate
Butterfly bush multiplies readily, both from cuttings you take with intent and from seed you will generally 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 surest route to more butterfly bush, and they hand you the very same cultivar you began with. Take soft green tips in spring or early summer, or woody stems while the plant is dormant from late fall into early spring. Dip the cut end in rooting hormone, hold the soil evenly moist, and softwood cuttings settle in roots in about 2 to 5 weeks.
SeedEasy
Self-seeds readily in the garden · One growing season to a small plant
Left unchecked the species sows itself in every direction, and a single stray seed becomes a small plant inside one season. That very ease is the drawback, because the wild species is invasive and regulated in parts of the country. Avoid sowing the straight species where it ranks 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.
The blooms do nourish adult butterflies, but the shrub offers their caterpillars no home, so it serves only half of the life cycle. The larger problem is seed: one flower cluster releases over 40,000 seeds, and the common species has spread into the wild far enough to earn regulated noxious weed status in Oregon and Washington. The graceful answer is to plant a sterile or seedless cultivar, or a native nectar shrub, and remove the spent spikes so it never seeds itself across the landscape.
Butterfly bush blooms on old wood, so you should never cut it back hard.
The shrub flowers on new, current-season wood, which is precisely why a hard cut serves it well rather than harming it. Bring it down close to the ground in late winter or early spring and it returns with vigorous fresh shoots and fuller flower spikes. In the coldest zones it tends to die back to the ground of its own accord regardless.