Hydrangeas (gouache style)

Mophead hydrangeas are forms of Hydrangea macrophylla, a shrub originally from Japan. Their rounded heads are made mostly of showy sterile florets, while lacecaps, the other main form, have a flat centre of tiny fertile flowers ringed by larger ones. On many coloured varieties, flower colour depends on the soil: blue on acid soil, where aluminium is available to the plant, and pink on alkaline soil. White kinds stay white.

Plant in autumn or spring in moist, fertile soil, ideally with morning sun and shelter from cold, drying winds. They're thirsty shrubs, so water well in dry spells and mulch in spring. Leave the faded heads on through winter to shield the buds below, then in March or April cut each stem back to the first strong pair of buds. Every few years, take out a few of the oldest stems at the base. To keep potted plants blue, use ericaceous compost and rainwater.

Mophead hydrangeas in blue, mauve and pink are painted here in loose brushwork. The three shades echo the way one variety can change colour with its soil, and that's part of their appeal. Loose strokes suit the soft, rounded flower heads, catching them in full colour at the height of their season.