Selection of heirloom varieties by observation has ensured the entirety of them is more-or-less right, for example, that the plants are easy to grow, the yield looks nice, tastes great, stores well and so on. They may not have as big a yield or such huge flowers as modern varieties but, in compensation, they generally don’t fail completely or need pesticides.

Like modern gardeners, those of old who bred our heirloom varieties needed crops which yielded well over a long season – for their home, as head gardeners serving a large house or as market gardeners supplying local customers. To do this, the plants generally needed to keep on producing new buds, because flowers are modified buds, for example, in the axils of new leaves (see left) or at the tip of stems. This means the plants had to keep on growing. Such indeterminate plants also generally become tall.

Many heirloom varieties have this trait, for example amongst peas, Hurst Green Shaft and the Victorian Colossal pea. Well-known heirloom climbing beans like Blue Lake common bean or Scarlet Runner bean easily make it up 2m canes.

As well as a long yielding season, such tall varieties also produce larger yields than dwarf types! Dwarf bean and pea varieties are generally grown by gardeners only as early short-season crops (or by commercial growers so they can be mechanically harvested).

But heirloom varieties don’t have to grow tall or sprawling to keep on yielding. Courgette (zucchini) varieties continue to produce young leaves but the inter-nodal (between leaves) length has been bred to be short. In this way, they can keep on producing the young fruits whilst remaining bushy,  unlike their sprawling cousins.

Even for the humble cabbages and cauliflowers, gardeners prefer the longer cropping season of genetically-variable, open-pollinated heirloom varieties to the modern, uniform F1 hybrids.

This long harvest period of heirloom varieties has another benefit: households have a long time to judge their yields and to reject bad ones. The complex flavour of old sweet corn varieties compared with modern super-sweet F1 hybrids is particularly notable.

Gardeners of old also needed reliability, so they could provide adequate food, to supply the cook of large households or paying customers. Modern householders still value this reliability because they have space for only a single variety of each crop in their small gardens. One year (2020), my over-wintered broad bean crop failed (a long story!) and replacement beans were virtually unavailable in shops; we bought spring cabbage and broccoli instead, OK but not so different from what we’d already been eating them all winter.

Heirlooms also often have ‘hidden’ strengths, appreciated only from long observation by gardeners. For example, Coco Sophie, an heirloom variety of beans, has a superior ability to combine with bacteria in the soil to ‘fix’ nitrogen and so can grow vigorously even under infertile soil conditions.

And another very important aspect of heirloom varieties is that, because they’ve been around a long time, pests and diseases have had many opportunities to break down their resistances and failed. This has resulted in most of them not utilising the strong, single gene (vertical) resistances of many modern varieties, possibly because such resistancesmay have been overcome long ago. But their weaker multigenic (horizontal) resistance can cope with most pests and diseases, maybe with a little help from their gardener.

I have grown Scarlet Runner beans for over 40 years; I’ve had to replant some after slugs attacked very young plants, especially transplants. But it was only when I tried modern varieties that I experienced mass attacks on mature plants by the black bean aphid, making a horrible sticky mess and killing plants when it was too late to replant.

It is these kinds of properties of heirloom varieties that ensure they more-or-less fit all the purposes of gardeners. And it is this fit for purpose property that participatory plant breeding can ensure is included in modern varieties, by selecting new varieties with gardeners and in their gardens!