F1 hybrids are the first generation of a hybrid cross, F2 is the next generation created by collecting seed from an F1 hybrid.

Annual F1 hybrids are a special case where two lines of plants are bred for a number of generations to create very inbred plants, usually quite weak in a number of areas. Then these two plants are crossed and the seed produces very vigorous plants, all of them very very similar. This way the grower can control very precisely the characteristics of the plants grown from seed. The ones that are sold have very desirable flowers, growth habits, insect resistance, etc. F1 seed is quite expensive because the weak inbred lines of plants must be maintained and crossed very carefully. It is good to choose an F1 where you need a well-defined growth pattern, height, or precise flower colours.

If you take seed from this type of F1 hybrid you get an F2 hybrid, with variation in the plants that are produced. Some will be quite similar to the F1, some will be like one or other of the parents of the F1, and some will be in between. Sometimes, these F2 hybrids are good enough for sale. They are much cheaper than the F1 because you just grab masses of seed off the F1s and grow them. If you are establishing a mixed border and need a lot of decent plants with different colours, then F2 is a good way to go.

I ll try to explain you in english....
FI and F2 is about crossing ...
Imagine you have two plants (example : one is white and the other is red )that you cross. This two parents will make two "babies" whith uniform caracteristics (pink flowers). This babies are named F1.
Afterwards, when you cross this babies (F1), they will produce hybrids named F2 (second generation). These F2 could be like the initial parents (red or white), or as the F1 generation (pink), or there could be a mix between them all.
You could obtain great variation.

What the differents in their culture???

F1 are very resistants from illness or little animals and very performant. But, they all make flowers at the same time and seeds are more expensive.
F1 procuce more seeds than F2

F2 give you more "original" flowers....because there are a mix of more different plant.

I hope that you will understand my explications.

Maybe, someone will be able to explain more fluently if my explications are not great.

Camille.

In french :
La premiere génération d'hybrides est uniforme. Si l'on croise à nouveau les hybrides F1, la seconde génération, F2,produit toute une gamme de formes diverses reflétant les traits : des parents, de la génération F1 et autres. Un éventail de formes plus ou moins éloignées des traits respectifs des parents originaires et de leurs hybrides F1.

It's very easier to explain it in french! ;-))

F1 indicates that your impatiens seeds is a cross (hybridized) but that you can count on the outcome, e.g. a package of red impatiens seeds will come out red.

F2 indicates that the seeds are harvested from F1 plants. you can not be sure of the outcome. E.g. because the seeds are harvested from a red impatiens, it does not guarantee that the new flowers will be red also.

If you buy plants (not seeds) then it really does not matter a whole lot. sometimes, F1 plants are more vigorous than F2 plants, but often the color is the main difference when it comes to impatiens.