Gardening is seldom described as an art form. It should be. Like a painter who squeezes different colours onto a palette, a gardener spots the plants that flower at the same time and then makes them bedfellows, especially if their flower colours complement each other. As I drove to work recently down the A44, I was greeted by huge swathes of blue-flowering common cranesbill on the road verges. A little further on, I noticed a great golden explosion of an evening primrose (Oenothera fruticosa, I think), in a cottage garden. The bright yellow cups of the latter would surely look very handsome in among a blue sea of one of the named varieties of blue cranesbill, such as Johnson’s Blue. Both these self-seeding plants have a long flowering period and such a mix would look all the more effective if planted on a large scale a useful solution on a grassy bank, perhaps?

During late summer, we can all be harvesting seed from flowers and vegetables. It has been a tradition in Europe since about bc10,000, the time when human beings opted for a settled, rather than nomadic, lifestyle. During those millennia, only seed from the strongest plants was selected, which resulted in gradual improvements in yield. There’s something very satisfying about collecting your own seed. In addition to the financial gain, it’s a way of life for the organic gardener, who is reassured of plant provenance. Don’t save the seeds from F1-hybrid cultivars as they will not come true. Runner and broad beans, especially on allotments, are often cross-pollinated with other strains: their offspring may vary in shape or colour, but this is of little importance to the amateur.

I spent a fascinating afternoon last year at Wakehurst Place, Sussex, the home of the Millennium Seed Bank. I was taken around by one of the botanists there, a distant cousin called Michael May. The tell-tale signs that seeds are ripe is when they rattle in their seed cases (for example, peas), when they or their cases have darkened in colour, or when the seeds cases split open. A viable seed will sink when placed in water. All you need to do is venture forth on a dry day armed with some old envelopes and a pencil, especially important if you’re collecting a lot of different seeds. When you get them home, they can be further dried for a few days, slowly and gently, on a tray or in an open paper bag in an airy, dry place. Larger seeds, such as those of beans and peas, benefit from one to two weeks out in the open air, or greenhouse/conservatory if rain threatens.

When it comes to tomatoes, they’re best cut in half when fully ripe, after which the seeds are gently squeezed or gouged out into a bowl of water. They are then flushed clean of detritus in a sieve and washed in a solution of soda crystals to remove the gelatinous layer (a germination inhibitor). Dry them (and other sticky seeds such as those of pumpkin) on a ceramic plate. When fully dried, seeds are easily placed in a tin or jar in labelled envelopes in a cool and completely dry room for the winter, where they shouldn’t come to any harm. Sachets of silica gel can be placed in airtight containers to ensure all seeds remain dry. Stored seeds last longer if kept in the refrigerator, but should be exposed to room temperature for a few days before sowing.

I was shopping for vegetables in the market the other day and the nice, smiley lady who sells them told me how one of her suppliers had lost 60 acres of broccoli and 160 acres of potatoes due to flooding, and that the price of vegetables is bound to rise. I’ve heard similar gloomy reports relating to allotment holders.It could be that seed will become scarcer as well. Make a note in your diary for next February to go to one of the ‘Seedy Sunday’ events. Started in Brighton about five years ago, this now famous seed-swapping event is spreading throughout the land consult www.seedysunday.org

For further reading, buy Sue Stickland’s Back Garden Seed Saving. And contact Garden Organic which used to be called the HDRA if you want to save seed of endangered species that are threatened by EU legislation.