Agapanthus ‘Double Diamond’

Agapanthus 'Double Diamond' (Agapanthus africanus hybrid) is a compact double white agapanthus that holds to about 50cm tall and 50cm wide, roughly half the size of the old roadside clumps. The pure white, fully double flowers sit just above an evergreen fan of strappy leaves through summer. Plant it when you want the flower without the bulk.

Why you'll love it

• Double white flowers. Densely petalled heads that read cleaner and last longer than a single flowered agapanthus.
• Compact enough for a small garden. It edges a path or fills a pot without taking the bed over.
• Genuinely tough. Drought, heat and salt tolerant, so a hot north facing strip or coastal front garden suits it.
• Evergreen structure. The strappy foliage holds the bed together for the nine months it is not flowering.
• Low maintenance. Cut the spent stems, feed once in spring, divide every few years.

Where it works best

Borders and edging. Plant 40cm apart. The clumps meet in the second season and the line stays even because every plant is the same compact form.

Mass planting. Also 40cm apart, about six plants per square metre, and reliable on a hot bank or nature strip where irrigation is not guaranteed.

Pots and coastal gardens. Happy in a 400mm pot for years and unbothered by salt laden wind. One caution: agapanthus sap and roots are toxic to pets, so think twice if you have a dog that digs.

Growing Agapanthus 'Double Diamond' in Australia

Position and climate. Full sun gives the most flower heads. Subtropical, warm temperate, cool temperate and Mediterranean gardens all suit it. It is rated for light frost only, so in cold inland and highland districts expect foliage burn in a hard winter; mulch the crown beforehand.

Soil. Almost any soil that drains, including poor sand and clay once the bed is raised. What it will not take is sitting wet through winter.

Water and feed. Water weekly through the first summer, then it carries itself on rainfall in most gardens. Feed a controlled release fertiliser in early spring; heavy nitrogen builds leaf at the expense of flowers.

Pruning. Cut spent flower stems at the base once the heads brown, tidy outer leaves in late winter, and divide congested clumps every four or five years to keep flowering strong.

What to expect when it arrives

It is grown in three sizes: tube stock, 140mm in packs of ten and 200mm in packs of six. Tubes are the value option for a long border; the larger packs give a fuller clump in the first season. Availability moves around, so check the size selector.

Expect a fortnight of stillness, then new leaves within a month in warm weather and the first flowering in the season after planting. Delivered Australia wide, with delivery from $29.95. Every plant carries our 30 day healthy plant guarantee.

Plant care guides and related reading

• Compare the full agapanthus range
• How to choose edging plants for a garden border
• Browse plants suited to mass planting
• Find coastal and salt tolerant companions

Common questions

Is it safe around cats and dogs?

No. Agapanthus sap and roots are toxic to pets if chewed, and the sap can irritate skin, so wear gloves when dividing.

Will it flower in shade?

It survives in part shade but gives far fewer heads. For a proper display give it at least six hours of direct sun.

Does it handle frost?

Light frost only. In cold districts the leaves may burn back over winter, though an established clump usually reshoots in spring if the crown is mulched.

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.