F1 vs Heirloom Seed: What Actually Matters

"F1The first-generation offspring of two specific, deliberately chosen parent plants, bred for a predictable, uniform result but not worth saving seed from. Full definition →" on a seed packet means the seed comes from crossing two inbred parent lines. F1 hybrids give especially uniform plants with good vigour and yield, but the seed costs more and seed you save will not come true. Open-pollinated varieties, which include heirlooms, breed true and the seed is cheap, but plants are usually less uniform, vigorous and productive. Pick by what you need.

What F1 means

F1 hybrids are produced by crossing two stable seed lines, called inbred lines, that give rise to especially uniform progeny with good vigour, yield and other properties. It says on the seed packet if a variety is F1. The greater vigour is called hybrid vigour (heterosis), and hybrids are more robust and better able to overcome adverse growing conditions. Uniformity of flowering, stature, yield and maturity period matters most to commercial growers, but hybrids offer worthwhile advantages to home gardeners too.

The catch is the cost and the seed. F1 seed is expensive because it has to be recreated by crossing the inbred parent lines again, and preventing self-pollination of the inbred lines, which leads to poor-quality plants called "selfs", is complicated and costly. Because breeders control the inbred lines, other seed companies cannot grow the hybrids, which keeps costs high. Seed saved from F1 plants will not produce plants that are true to the parent type. Maintaining the lines also means hybrids are often offered for only a few years before coming off the market, leaving gardeners to seek a replacement for a favourite.

What open-pollinated means

When a group of selected plants are grown together and allowed to pollinate each other, by insects, wind or by hand, the seed is open-pollinated. It will grow a variety that breeds true to type, and the plants carry their parents' characteristics. Open-pollinated varieties are also inherently genetically variable: each plant is slightly different from every other, and that variation allows them to respond to different growing conditions. Before hybrids, all seeds were open-pollinated. They are the only option for plants that cannot be easily inbred, such as lettuces, peas and runner beans, and open-pollinated seed is available for all crops offered as hybrids, though it is usually significantly less uniform, vigorous and productive.

The trade-off is cross-pollinationPollen moving from one plant to a different, compatible variety, needed for fruit to set on any variety that isn't self-fertile. Full definition →. Pollen moved by bees or wind from another variety can cause quite significant variations from the parent plant, particularly in brassicasThe cabbage family: cabbage, kale, broccoli, cauliflower, Brussels sprouts, kohlrabi, swede, turnip and more, sharing the same pests, diseases and rotation rules. Full definition → and squashes. Peas and French beans generally do not cross-pollinate.

At a glance

F1 stands for first filial generation, the first generation from crossing the two parent lines. Heirloom is not a separate breeding category: the word usually means an open-pollinated variety with a long history of saved seed, often older than the first modern hybrids. An open-pollinated variety grown and saved in the same spot over several seasons can adapt to it, which a remade F1 cannot (Garden Organic). Seed swaps only work with open-pollinated seed, and the realistic crossing risk is a neighbouring plot-holder's variety flowering at the same time. Hybrid vigour depends on the specific cross, and some open-pollinated varieties are valued for a flavour that hybrids have not always matched, though that varies by variety.

Which to choose

Choose F1 when uniformity matters: a crop meant to mature together, or a variety bred for a named disease resistance. Choose open-pollinated when you want to save seed, when the cost of buying seed every year is not worth it, or when you are growing lettuces, peas or runner beans, where open-pollinated seed is the only option. Choosing on principle, all F1 or all heirloom, rather than crop by crop usually means the wrong tool for some jobs. For example, the tomato 'Sungold' is an F1 and 'Moneymaker' is open-pollinated. In a short Scottish season, uniform ripening can help a crop finish before the first autumn frost, which matters for borderline outdoor crops such as tomatoes and squash. Salad leaves and courgettes are different: staggered cropping suits them better than one glut, so uniformity buys little.

Blight resistance

Blight is most common in warm, wet weather, and the tomato growing guide explains why outdoor tomatoes in Scotland are at risk. For tomatoes, check for resistance in a named cultivar rather than assuming it from the F1 label. 'Crimson Crush' and 'Mountain Magic' performed very well at Wisley in 2021, when blight was extremely widespread and susceptible cultivarsA plant variety that arose or was bred under cultivation and is kept true by deliberate propagation, rather than a naturally occurring wild species. Full definition → were severely affected (RHS), but new strains of the pathogen could overcome resistance at any time. Seed potatoes are tubersA swollen underground stem or root a plant uses to store energy, which can also grow into a new plant, the classic example being a potato. Full definition →, not seed, so potato resistance sits outside the F1 choice: Athlete, Alouette, Carolus and the Sarpo cultivars are currently thought to show good resistance, while older cultivars such as 'Cara', 'Kondor', 'Orla', 'Markies' and 'Valor' no longer do. See the tomato blight page.

The Scottish-linked tomato 'Ailsa Craig' was introduced in 1908 by Alan Balch, but accounts differ on where he bred it, and its name may come from the island or from a motor yacht.

Common questions

Sources