Shrubs, trees and climbers

Butterfly bush

BuddlejaScrophulariaceae
Also: Buddleja, Summer lilac
AT A GLANCE
Full sun Water: little H6down to −20 °C 2–3 m tall · 2–3 m wide In a pot: yes
Flowering · UK
Flowering · Northern Italy
Flowering · Central Italy
Flowering · Southern Italy and islands

Cut back hard even in the first spring after planting — this genus flowers on new wood and responds well to a confident hard prune from the start.

Care

Light

Full sun.

Water

Drought-tolerant once established.

Soil

Adaptable, free-draining soil of low to moderate fertility; tolerates poor soil, even rubble or waste ground.

Pruning

Cut back hard in early spring, to a low framework around knee height — flowers on the current season's growth, so hard pruning produces a better display.

Feeding

Needs no feeding — it grows out of railway walls and rubble. On a garden soil the hard spring prune plus a light mulch is all the input it wants; fed, it makes enormous soft stems that break in wind.

Propagation

Hardwood cuttings in late autumn are almost comically easy: a pencil-thick length of the year's growth pushed into soil in a spare corner, left alone, roots by spring. It also self-seeds, sometimes to the point of nuisance.

Month by month

Months change with the climate: in southern Italy tomatoes go out two months earlier than in England.

  1. MarchCut back hard to a low framework. how ›
  2. AprilLight feed as growth resumes. how ›
  3. JulyDeadhead spent flower spikes to prolong flowering and prevent excessive self-seeding. how ›

Months based on climate: UK. Your choice stays on this device.

  1. MarchCut back hard to a low framework. how ›
  2. AprilLight feed as growth resumes. how ›
  3. JulyDeadhead spent flower spikes to prolong flowering and prevent excessive self-seeding. how ›

Months based on climate: Northern Italy. Your choice stays on this device.

  1. FebruaryCut back hard to a low framework. how ›
  2. MarchLight feed as growth resumes. how ›
  3. JulyDeadhead spent flower spikes to prolong flowering and prevent excessive self-seeding. how ›

Months based on climate: Central Italy. Your choice stays on this device.

  1. FebruaryCut back hard to a low framework. how ›
  2. MarchLight feed as growth resumes. how ›
  3. JulyDeadhead spent flower spikes to prolong flowering and prevent excessive self-seeding. how ›

Months based on climate: Southern Italy and islands. Your choice stays on this device.

Common problems

Self-seeding

How to spot it. Into unwanted places — a vigorous coloniser.

What to do. Deadhead before seed sets to control spread.

How to spot it. On soft new growth.

What to do. Encourage predators.

Powdery mildewfull sheet ›

How to spot it. In dry summers.

What to do. Improve airflow.

Popular varieties

Buddleja ‘Black Knight’AGM2.5–3 m × 2.5–3 m · July–SeptemberJuly–SeptemberJuly–SeptemberJuly–September
Buddleja ‘Buzz’1.2–1.5 m × 1.2 m · July–SeptemberJuly–SeptemberJuly–SeptemberJuly–September
Buddleja ‘Royal Red’2.5–3 m × 2.5–3 m · July–SeptemberJuly–SeptemberJuly–SeptemberJuly–September

Questions

Butterfly bush: is it hardy?

H6: Hardy in the vast majority of UK gardens. It survives down to −20 °C.

Can it grow in a pot?

For a season or two, though naturally a large shrub best suited to open ground.

Butterfly bush: when do you prune it?

Cut back hard in early spring, to a low framework around knee height — flowers on the current season's growth, so hard pruning produces a better display. In the calendar for UK, pruning falls in March.

Butterfly bush: when does it flower?

In the climate of UK it flowers in July–September.

When do you feed it?

Needs no feeding — it grows out of railway walls and rubble. On a garden soil the hard spring prune plus a light mulch is all the input it wants; fed, it makes enormous soft stems that break in wind.