The first filial generation (first-generation hybrid) produced by cross-pollinating two compatible parent plants is known as the F1.
The F1 often brings together the best of desirable qualities from both parents. The second generation is referred to as an F2 hybrid.
Many plants we buy from garden centres and breeders are F1s. These have a range of appealing characteristics, as discussed above. They are often sterile, but even if they are not they rarely breed true.
Producing hybrids offers the opportunity to mix the genes of two or more different plants, combining their desirable traits or creating new characters. Their diverse genetic make-up means hybrids are usually very vigorous plants, often highly floriferous or heavy-cropping, making them important in the vegetable and seed trades.
How to Write Hybrid Names
Plants produced by crossing different species, for example Viburnum farreri and V.grandiflorum. Indicated by an x before the species name. Can occur in the wild but are more common in cultivation. (Note here that Viburnum is the genus.)
Viburnum x bodnantense
Plants derived from crosses between two or more genera, such as Heuchera and Tiarella. Indicated by an x before the composite genus name.
x Heucherella ‘Stoplight’
Mostly used to refer to annual and vegetable cultivars produced by crossing two stable seed lines that give rise to uniform progeny:
tomato ‘Cristal’ F1, sunflower ‘Harlequin’ F1
Plants grown from F1 hybrids are called F2 hybrids and display much greater variation than their parents.
Pelargonium ‘Speedy’, mixed F2
Seeds harvested from garden plants will not always come true to their parent, particularly if the parent is a hybrid or there is a related plant nearby it could have hybridised with, but can be a valuable means of raising new cultivars.
If this is a new area for you, you might like to begin with this interesting short introductory film from BBC4: