Agapanthus Cool Steel

Agapanthus 'Cool Steel' (Agapanthus 'Cool Steel') holds steel blue flower heads on stiff upright stems above a clump of strappy evergreen leaves. It reaches about 90cm tall in flower and 60cm across, small enough for a front border but substantial enough to plant in drifts. The colour is cooler and greyer than the common garden agapanthus, and it holds rather than bleaching out in summer heat.

Why you'll love it

• Stems that stay standing. The flower scapes are strong and straight, so a summer storm does not leave the display lying across the path.
• Green through winter. The foliage is evergreen, so the bed still reads as planted when nothing is in flower.
• Genuinely hard to kill. Frost hardy, drought tolerant, salt tolerant and content in poor soil, so it suits beds nobody waters.
• Busy with bees. Each head opens dozens of small trumpets over several weeks, and bees and butterflies work them steadily.

Where it works best

Mass planting. Plant 50cm apart and the clumps knit into continuous foliage within about two seasons, the flower heads reading as one blue band rather than separate plants.

Borders and edging. The same 50cm spacing suits a single line along a path, set back 40cm from the edge so the leaves do not sprawl over paving.

Coastal gardens and pots. Salt tolerance suits exposed coastal blocks, and a pot 400mm or wider holds a clump for years.

Growing Agapanthus 'Cool Steel' in Australia

Position and climate. Full sun brings the most flower stems; in part shade you get good foliage and fewer heads. It suits cool temperate, warm temperate, subtropical and Mediterranean gardens, and is frost hardy once established. In humid tropical gardens crowns can rot over a long wet summer, so drainage matters more there.

Soil. Almost anything that drains. It performs in sand, gravel and tired clay alike, though compost through the planting hole speeds it up.

Water and feed. Water weekly through the first summer, then only in long dry spells. A handful of complete fertiliser in early spring is the only feeding it asks for.

Pruning. Cut spent flower stems off at the base once the colour has gone. That keeps the clump tidy and stops seed setting, which matters where garden agapanthus has spread into bushland.

What to expect when it arrives

This one is grown as tube stock, so the plant in the box is young: a small fan of leaves and a developing root system, not a flowering clump. That is why tubes are the sensible way to plant a long border. Expect leaf growth in the first season and the first real flush of stems in the second summer.

The tough foliage travels well. 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
• Choosing edging plants for paths and driveways
• Plants that suit mass planting
• Salt tolerant plants for coastal gardens

Common questions

How far apart should I plant it?

Fifty centimetres apart for mass planting or a solid edge. Closer than that and the clumps compete for light, which thins the foliage at ground level and costs you flower stems.

How long until it flowers from a tube?

Usually the second summer. A few throw a stem in the first season, but the clump needs a year to build the roots that support a proper display.

Is it safe around cats and dogs?

No. Agapanthus sap and roots are toxic to cats and dogs, and the sap can irritate human skin as well. Wear gloves when you divide it.

Can I grow it in a pot?

Yes, and it flowers well slightly crowded. Use a pot 400mm or wider with free draining mix, then lift and divide every three or four years.