Honesty, Jupiter's beard, Stonecrop - their country names alone are reason enough to grow these three common herbaceous plants, but they have further qualities. In any small patch of sunny ground, in ordinary soil, these utterly easy-to-grow plants will look after themselves season after season. From spring to autumn, one or more of them will be in flower - in shades of deep-pink, rusty-red and purple - and in winter there will be seedheads for the frosts to encrust. Best of all, their nectar-rich flowers are irresistible to insects - beloved by butterflies and bees.

The Honesty, Lunaria annua, flowers first, in late spring or early summer. It is a biennial plant which maintains its presence by seeding profusely, so that there are always new plants to continue the cycle. The cross-shaped flowers of "Munstead Purple" are deep reddish purple and carried 2ft to 3ft in the air on stems clothed with heart-shaped leaves, incised around their edges.

But, beautiful as the flowers are, Honesty is best known for its seed cases - papery discs, like translucent coins, which remain attached long after the stems have died. Their appearance has given Honesty its botanical name Lunaria, from the Latin word luna, the moon. Like the moon, these discs are commonly silver, but in this variety they are flushed purple.

Jupiter's beard, Cetranthus ruber, flowers next - profusely and over a long period. From late spring to late summer its blooms, pale pink to dark crimson, mingle with the purple-tinted moons. When this first flush has faded, a good trim with the shears usually ensures a second late harvest of flowers.

Finally, the Stonecrop, Sedum 'Autumn Joy'. Few herbaceous plants look so good for so long. Its succulent-like leaves, glaucous and pale, its solid air and bold outline, and its dense, flat-topped flower heads, all make it an excellent contrast and fine companion to almost anything you care to plant it with.

The wide, pale-green flower heads, like broccoli florets, form during the summer. They open in early autumn, a sheet of rich pink, tiny, star- shaped flowers - a platform of nectar for feeding insects. The flowers darken slowly to copper-red and then fade with the season until brown seedheads remain, supported on hollow, woody stems. If you don't cut them down they will accompany the seed capsules of the Honesty through the winter, and by the time you get round to it in the spring, new knobbly shoots will already be emerging.

John the Gardener