Irises (gouache style)

Bearded irises take their name from the fuzzy strip, or beard, on each of the three lower petals, called falls. Above them stand three upright petals known as standards. They grow from thick rhizomes and have sword-shaped leaves arranged in fans. Gardeners group them by height, from dwarf to tall bearded. The name iris comes from the Greek word for rainbow, which suits a flower bred in almost every colour.

Plant or divide rhizomes from July to September, after flowering, with the top half sitting above the soil so the sun can bake it. They need full sun and good drainage, and they don't want a mulch covering the rhizomes. A low-nitrogen feed in early spring helps, since too much nitrogen leads to soft, floppy growth. Cut off faded flower stems in early summer. Every three to five years, lift congested clumps, discard the old woody centre and replant healthy pieces.

Tall bearded irises in deep purple and pale blue are the subject here. The two shades show something of the iris's range, from rich, dark tones to soft and pale ones. They're painted at full height in flower, the brief early summer moment that the whole year's growth builds towards.