Herbaceous perennials are the mainstay of many a garden throughout the summer.

Non-woody, flowering plants that die down in winter and come up afresh each spring, they are tough, reliable, and easy to look after, requiring only a moderately fertile soil, an occasional topdressing with organic material, and their dead stems cutting down in winter.

None of us should be without a good sprinkling of these stalwarts, since they are guaranteed to flower for several months each year.

Garden centres and nurseries have good stocks in spring and, although they can be planted at almost any time of year, planting now will give them plenty of time to settle in to your garden before they become dormant next winter.

Faced with a choice of buying either one large plant or three smaller plants for the same money, I would always go for the three.

A group will look better than a single plant and, because perennials generally grow quickly, the smaller plants will soon make up.

On the other hand the larger plant will probably flower more profusely in its first year and, if you are careful, you can often manage to divide it into three before planting anyway.

You pays your money and takes your choice...

An even cheaper way of acquiring groups of perennials is to grow your own from seed.

This takes a bit longer than a trip to the nursery, but it's much more satisfying in the long run and should provide you with enough material to plant in large drifts.

Seeds can be germinated on a windowsill, in the greenhouse or simply in a sheltered spot out of doors.

Sow them as for any other seeds - in seed compost in shallow pots, covering the surface of the pots with a thin layer of gravel or grit.

Perennials can take a bit longer to germinate than annuals do; the grit helps prevent the compost from drying out, and stops annual weed seeds blowing in.

This year at Brockhole we have sown seeds of the perennials Eryngium, Echinacea, Oenothera and Dicentra.

If germination is slow or erratic, we gently prise out any seedlings big enough to pot up, leaving the rest of the pot undisturbed.

This means that any seeds left in the pot can come up in their own good time.

The seedlings are potted up into two or three inch pots grown on in the cold frame until they are big enough to plant out.

To give the small plants a good start, it helps to add a generous amount of organic material to the soil before planting.

Thereafter they should be quite capable of looking after themselves.