Iris Louisiana Mauve

Iris Louisiana Mauve (Iris x louisiana 'Mauve') is the iris for ground that stays wet. It grows to about 90cm tall and 60cm across, lifting broad mauve and purple flowers above the strappy foliage in spring. Most garden plants sulk in a boggy corner. This one treats it as home, so it is the obvious choice for a pond margin or a bed that never quite drains.

Why you'll love it

• It thrives where drainage is poor. Damp beds, dam edges and pond margins in up to 100mm of standing water all suit it. It also grows in ordinary garden soil, provided it never dries out.
• Big spring flowers. Broad blooms on tall stems that read from across the garden.
• Frost hardy and heat tolerant. It handles cold southern winters and hot subtropical summers.
• It spreads into a colony. Rhizomes multiply steadily, so a small planting thickens into a solid clump within two or three seasons.

Where it works best

Mass planting and water margins. Plant 40cm apart. The clumps merge into a continuous band in two seasons, which is what a pond edge or drainage swale needs.

Borders and edging. The upright leaves give structure to a mixed border all year, and at 90cm it sits in the middle rank.

Feature planting and pots. A single clump makes a strong vertical accent beside water. Use a pot 400mm or wider; drainage is not a concern, since this is one of the few plants happy to sit in a saucer of water.

Growing Louisiana iris in Australia

Position and climate. Full sun gives the best flowering, though it takes a few hours of shade in hot inland gardens. It suits warm temperate, cool temperate, subtropical and Mediterranean climates, and is frost hardy enough for cold southern winters.

Soil. Rich, heavy and moist is ideal, and clay is an advantage. Slightly acidic soil gives the strongest colour, so avoid lime. Mulch 50mm deep over the rhizomes without burying them; they sit at or just below the surface.

Water and feed. Keep the soil damp, especially from bud formation through flowering. Feed with a complete fertiliser in early spring and again after flowering. Louisiana irises are hungrier than most and reward feeding with bigger blooms.

Pruning and division. Cut spent flower stems at the base and trim tired foliage in late summer, when growth slows and the leaves die back in cooler gardens. Lift and divide every three to four years, replanting the outer rhizomes and discarding the woody centre.

What to expect when it arrives

These are grown in 180mm pots and sold in packs of six, the right quantity for mass planting. Each pot holds an established clump of rhizomes with foliage, ready to plant at 40cm spacing.

Foliage can arrive creased or yellowed at the tips, and the plant grows through it within weeks. Depending on the season you may receive plants with cut back foliage, which is normal and does them no harm. Expect flowers in the first or second spring after planting. Plants are delivered Australia wide, with delivery from $29.95, and every plant carries our 30 day healthy plant guarantee.

Plant care guides and related reading

• Best water plants for Australian garden ponds
• Managing a waterlogged garden bed
• Plants for consistently damp ground
• Compare options for mass planting

Common questions

How far apart should I plant them?

Forty centimetres apart, roughly six plants per square metre.

Is it safe around pets?

No. Iris rhizomes are toxic to cats and dogs if dug up and chewed, and can cause vomiting and drooling. Plant them where a digging dog is unlikely to reach.

Why has mine stopped flowering?

Usually a crowded clump, too much shade, or dry soil through spring. Divide every three to four years, feed in early spring, and keep the water up while buds are forming.