Double Blue Boy Agapanthus

Double Blue Boy Agapanthus (Agapanthus 'Double Blue Boy') takes the most reliable performer in Australian landscaping and doubles the payoff: full, layered heads of rich blue double flowers on strong 80cm stems above tidy strappy clumps. It masses like any agapanthus, at 40cm spacings into an unbroken summer border, and survives like one too, handling frost, drought, heat, salt and poor soil without complaint.

Why you'll love it

• Double the petals. Each head is a dense sphere of layered blue trumpets, noticeably fuller than common agapanthus and a magnet for bees and butterflies.
• The proven survivor. Agapanthus line Australian driveways for a reason: almost nothing kills an established clump.
• Neat between shows. The glossy strap foliage stays a tidy 40cm to 50cm mound all year, smothering weeds as it thickens.
• Made for repetition. Rows and drifts read beautifully: one variety, planted rhythmically, is the cheapest designer trick in landscaping.
• Cut flowers by the bucket. The tall stems last well over a week in a vase.

Where it works best

Borders and edging. Plant 40cm apart along paths and drives for a continuous flowering ribbon; a 4m edge takes 10 or 11 plants.

Mass planting and slopes. Drifts across banks and retaining wall tops bind soil and suppress weeds while they flower.

Coastal beds. Front line salt wind is no obstacle.

Pots. Clumps flower generously even slightly potbound in a 30cm to 40cm container.

Growing Double Blue Boy in Australia

Position and climate. Full sun brings the most flowers; light shade is acceptable with fewer stems. It thrives in subtropical, warm temperate, cool temperate and Mediterranean climates and is frost hardy once established.

Soil. Almost any soil with basic drainage. Improve pure sand with compost for faster clumping.

Water and feed. Water weekly for the first summer; after that, rainfall is generally enough, with a deep drink in long dry spells to keep flowering strong. A spring feed of controlled release fertiliser lifts the display.

Maintenance. Cut spent flower stems at the base after the show, and divide crowded clumps every four or five years in autumn. As a sterile double form it sets little to no viable seed, so it stays where planted rather than seeding about.

What to expect when it arrives

Double Blue Boy ships in 140mm pots in packs of 10, the format built for borders and drifts. It is grown to order and shows as backorder: we confirm timing with you before anything is charged or shipped. Plants establish quickly, usually flowering their first summer and hitting full stride by the second. Delivery is Australia wide, from $29.95, and every plant carries our 30 day healthy plant guarantee.

Plant care guides and related reading

• Browse the agapanthus range
• Plants for mass planting
• Plants for retaining walls and slopes

Common questions

Will it become a weed like old agapanthus?

No. The double flowers are effectively sterile, setting little to no viable seed, so it delivers the classic look without the self seeding older strains are criticised for.

When does it flower?

The main display runs through summer, typically December to February, with the odd bonus stem either side in warm gardens.

Why has my clump stopped flowering?

Usually deep shade or overcrowding. Move it into sun or lift and divide in autumn, replanting the strongest outer divisions, and flowering returns the next summer.

Is it safe for pets?

No. Agapanthus sap is an irritant and the plant is toxic to cats and dogs if chewed, so plant it away from pets that graze and choose from our pet safe range for those areas.

Western Australia: this plant is listed as an environmental weed in WA, where it escapes from gardens into bushland. We do not recommend it for WA gardens. Please choose a local alternative.