Agapanthus ‘Cool Steel’

Agapanthus 'Cool Steel' (Agapanthus africanus hybrid) is the pale silvery blue agapanthus, a long way from the harsh purple most gardeners picture. Flower stems reach about 1m over a clump 60cm across, and the heads open a soft steel blue that fades almost to white at the throat. The stems are strong enough to stand through summer storms rather than lying across the path, which is what separates a maintained border from a messy one.

Why you'll love it

• A softer, more refined blue. The silvery tone sits comfortably with white, grey foliage and rendered walls where a strong purple would fight the scheme.
• Evergreen structure. The strappy clump stays green year round in most gardens, so the border still reads as planted through winter.
• Hard to kill. Frost hardy, drought tolerant, heat tolerant and salt tolerant, which covers most difficult front garden conditions.
• Bees and butterflies love it. Each head works as a landing platform for weeks through the flowering season.

Where it works best

Mass planting. Plant 50cm apart through a bed or across a bank. At that spacing the foliage closes over within two seasons, shading out weeds and giving an even wall of flower stems in summer.

Borders and driveway edging. The same 50cm spacing gives a clean repeated line, and the 60cm clump width fills the space without spilling onto the concrete.

Coastal gardens and pots. Salt and heat tolerance suit exposed beachside blocks, and a 400mm pot holds a single clump that flowers just as heavily.

Growing Agapanthus 'Cool Steel' in Australia

Position and climate. Full sun produces the most flower stems. It performs across subtropical, warm temperate, cool temperate and Mediterranean gardens, and it is frost hardy, so cold southern and tableland gardens are fine. In the humid tropics flowering is less reliable.

Soil. It grows in almost anything that drains. Sandy coastal soil and thin, poor ground are both acceptable. On heavy clay, raise the bed and work compost through it so the crown never sits in water.

Water and feed. Water weekly through the first summer, then only during long dry spells. It is genuinely drought tolerant after two seasons. Use a complete slow release fertiliser in early spring and skip high nitrogen feeds, which push leaf at the expense of flower.

Pruning. Cut spent flower stems at the base as they brown, which keeps the clump tidy and stops seed spreading into bushland. Divide crowded clumps every four or five years.

What to expect when it arrives

It is grown in three sizes: single tubes, 140mm pots in packs of ten and 200mm pots in packs of six. Tubes are young divisions with a small fan of leaves and take two summers to flower properly. The 140mm and 200mm plants are established clumps and many flower in their first season. Both pack sizes are currently on backorder.

Strappy foliage travels well, and a few bent leaves on arrival will grow out. Delivered Australia wide, with delivery from $29.95 and a minimum order of $300 before delivery, and every plant is covered by our 30 day healthy plant guarantee. One caution stated plainly: agapanthus sap is toxic to cats and dogs and can irritate skin, so wear gloves when dividing.

Plant care guides and related reading

• See the full agapanthus range
• Plants suited to mass planting
• Building a waterwise garden
• Salt tolerant plants for coastal gardens

Common questions

How far apart should I plant it?

Fifty centimetres apart for a border run or mass planting. Each clump reaches about 60cm across, so at that spacing the leaves just overlap and the bed reads as continuous rather than spotty.

Is it safe around pets?

No. Agapanthus sap is toxic to cats and dogs if chewed. The risk is low in practice, but it is not the plant for a pet that grazes on foliage.

Why is my agapanthus all leaf and no flower?

Usually too much shade, too much nitrogen, or a congested clump. Move it into full sun, switch to a complete slow release fertiliser in early spring, and lift and divide it if it has not been split in five years.