Quick Guide: summer, hardy, semi-shade, height: 60cm/24in, width: 30/12in

The oenothera family of North America includes the evening primrose, O. biennis. Most species bear yellow flowers, though some are white. Lightly scented, they are funnel-shaped at first but open almost flat. They bring prolonged and brilliant colour to the border, and because they s&-seed freely are also good for wild gardens.

GROWING Set out small groups of young plants in the autumn, on light, free-draining soil. Oenotheras like an open, sunny site but will tolerate light shade. Water well in dry weathcr and dead-head regularly unless you want plants to self-seed. Cut down the stems after flowering.

PROPAGATION Divide established plants between autumn and spring. These perennials are short-lived but self-seed freely and successfully.

SPECIES O. perennis, syn. O. pumila, small, yellow flowers, pale green leaves, mid-summer; 0. missouriensis, suitable for rock gardens or the front of the border at 15 cm/6in high, abundant yellow flowers all summer; O. fruticosa, the variety `Yellow River' bears a profusion of deep golden yellow flowers, mid-summer; O. tetragorra 'Fireworks' (above) bears ye11ow flowers throughout the summer.

POSSIBLE PROBLEMS Heavy, waterlogged soil encourages root rot.