Ornamental onion, Allium, single purple spherical flower on a stem isolated in shallow focus against green leaves.

Rose mallow, Hibiscus syriacus 'Blue Bird', purple blue flower and bud growing on a shrub against a green background.

Ornamental onion, Allium, single purple flower on a stem isolated in shallow focus against green leaves.

Rose mallow, Hibiscus syriacus 'Blue Bird', single purple blue flower growing on a shrub.

Rose mallow, Hibiscus syriacus 'Blue Bird', purple blue flower and buds growing on a shrub against a green background.

Rose mallow, Hibiscus syriacus 'Blue Bird', single purple blue flower growing on a shrub against a green background.

Iceland poppy, Papaver nudicaule, close-up detail of a single orange flower with yellow stamen against a green leafy background.

Boston ivy, Parthenocissus tricuspidata, close-up detail of a single fallen red leaf on grey stone in the autumn.

Plants, Flowers, Tulipa, Single closed tulip flower growing in a garden in spring.

Plants, Flowers, Tulipa, Single closed tulip flower growing in a garden in spring.

Plants, Flowers, Tulipa, Single closed tulip flower growing in a garden in spring.

Plants, Flowers, Helleborus orientalis, Hellebore, Backlit pink flowering hybrid Lenten rose.