The primula family comprises a number of hardy perennials including Primula veris, the cowslip, and P. vulgaris, the primrose. The polyanthus is a hybrid of these two.

The mallow, Malva alcea, is a tall, bushy plant particularly useful on poor soils. It bears abundant mauve trumpet-shaped flowers all summer.

Pulmonarias are ideal plants for a shady part of the garden, where they will spread their handsome oval leaves to make dense ground cover. In early spring clusters of drooping bellshaped flowers appear, held clear of the foliage on erect stems

A native of California, Mentzelia lindleyi is distinguished by stunning, bright yellow flowers 5cm/2in wide with glossy heart shaped petals. Numerous fine gold stamens cluster in the centre of each flower.

Astilbe species come from China and Japan. From these the garden hybrid A. x arendsii (above) has been developed to display the best qualities of the family

Ageratum houstonianum is a native of Mexico and is sometimes listed as A. mexicanum. It produces mounds of small, soft-looking, daisy-like flowers amid heart-shaped leaves.

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.

The bellflower family includes a great number of attractive species including Campanula medium, the well-loved biennial Canterbury bell, and several exquisite alpine plants.

Commonly known as snapdragon, Antirrhinum majus is a perennial usually treated as an annual, although in very favoured areas it may survive the winter.

Native to North America, the coreopsis is an accommodating plant, producing cheerful yellow star-shaped flowers throughout the summer even in polluted atmospheres.