Double Diamond Agapanthus

Double Diamond Agapanthus (Agapanthus 'Double Diamond') is a compact white form that carries layered double flowers rather than the usual single trumpets. The clump holds at about 50cm tall and 50cm wide, so it edges a path or fills a pot without the sprawl of an old fashioned agapanthus. Pure white heads over dark green strappy foliage are the reason to choose it.

Why you'll love it

• Double flowers, fuller heads. Extra petal layers give a rounder, denser head than a single agapanthus, and it reads clearly from across a garden.
• White that works at dusk. White flowers hold their brightness in low light, which makes this a good choice beside an evening entertaining area or a lit path.
• Compact and tidy. At 50cm it stays where you plant it, so a border edge keeps its line instead of collapsing outward each summer.
• Genuinely tough. Frost hardy, drought tolerant, heat tolerant and salt tolerant, which covers coastal blocks, hot courtyards and cold southern gardens.

Where it works best

Borders and edging. Plant 40cm apart for a continuous run. The clumps close within two seasons and stay even, since every plant reaches the same modest size.

Mass planting. Hold the same 40cm spacing across a bank or a nature strip. Once closed, the foliage shades the ground and takes most of the weeding out of the job.

Pots, balconies and coastal gardens. Three plants fill a 400mm pot, and salt tolerance means an exposed balcony or a front fence line is no trouble.

Growing Double Diamond agapanthus in Australia

Position and climate. Full sun brings the most flower heads. It tolerates part shade, though the trade is fewer flowers on longer stems. Subtropical, warm temperate, cool temperate and Mediterranean gardens all suit it, including frosty inland and southern districts.

Soil. Undemanding, provided the bed drains. Sandy and rocky ground is fine. What it will not accept is soil that stays sodden through winter, which rots the fleshy roots. Mulch 50mm deep and keep it off the crown.

Water and feed. Water weekly through the first summer, then only during long dry spells. Apply a complete slow release fertiliser in early spring for flower numbers, and avoid high nitrogen feeds that push leaf growth instead.

Tidying and division. Cut finished flower stems off at the base to keep the planting clean. Every four or five years, lift crowded clumps in autumn, split them and replant at the same spacing.

What to expect when it arrives

It is sold as tubestock, as 140mm plants in packs of ten, and as 200mm plants in packs of six. Tubes are small divisions with a few leaves that usually need two summers before flowering well, which makes them the economical choice for a long border. The 140mm and 200mm plants are established clumps and most flower in their first full summer.

Fleshy roots carry their own reserves, so agapanthus travels well and settles quickly. Plants are 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
• Low maintenance plants for full sun
• Plants that suit a balcony
• Plants for coastal gardens

Common questions

What makes it a double agapanthus?

Each flower carries extra layers of petals instead of a single set, so the head looks fuller and rounder. It is a selected garden form, not a different species, and it grows like any other agapanthus.

Is it safe around cats and dogs?

No. Agapanthus is toxic to cats and dogs if eaten, and the sap can irritate skin. Wear gloves when dividing clumps, and keep it away from a pet that chews at foliage.

Can I grow it in a pot long term?

Yes, and it flowers well when slightly crowded. Use a pot at least 400mm wide with drainage holes, and split the clump every three or four years before it pushes the pot apart.