The F2 seeds will produce various crosses that you will have to select from, grow out those F3 seeds, select from them, grow those F4 seeds, select, etc.

It can take several generations to produce a stable cross. Many of those on the Hybridizing forum here are working on 7th and 8th generation of various types of crosses.

Dave

So will the F1 seed all throw the same melons? or will they be like the F2 and F3 and so on and so forth?

I know this is an old thread, but I have stuff to say and the last post was a question. Anyway, yes. The F1 seeds should all be the same (they will express all the dominant traits between both parents), unless one or both of the parents weren't stabilized. When you cross-pollinate a female Congo flower with Moon and Stars pollen, if that fruit grows and produces seeds, those will be F1 seeds (and all the crossed plants resulting from those seeds should have stars on the leaves, since that's a dominant trait; if they don't have stars, then something else pollinated those Congo seeds; one unit of pollen corresponds with one seed; so all the seeds in a single fruit do not necessarily have the same father). If you grow out your F1 cross and save seeds, those will be F2 seeds, and that's when every seed should be less predictable.

Anyway, I know the stars are dominant, because I grew Moon and Stars last year, for the first time, along with about 14 other kinds of watermelons, and I saved seeds. This year, several of them have stars on the leaves (e.g. Fairfax, Wondermelon, King Winter, Ledmon, Tom Watson, Weeks NC Giant, Daisy and maybe others). Anyway, I'm pretty excited about all the crosses (especially since I know exactly what some of them are; Ledmon and Fairfax may have been crossed the year before with something else, too). My Moon and Stars last year didn't have any moons, though (it just had stars). We'll see if any get moons, this year.

I'm growing Congo this year, from saved seeds (but I didn't grow it last year with Moon and Stars; I grew it the year before with some other melons).

The stars are a really nice trait for breeding F1 hybrids, since it's a dominant trait you see when the plant is very young, and it's an easy way to see if your cross was successful.

I just noticed the question title, though, which indicates Moon and Stars is the mother (e.g. Moon and Stars x Congo). It'll be harder to tell if the cross took there, since the F1 leaves should have stars no matter what pollinates it. (The F2 leaves could have stars or no stars, though. If it has no stars, and you save the seeds from one without stars, then all its descendants should have no stars, unless they're crossed again with something that has stars, or unless it's a mutation or something.)

I let my plants cross naturally. I just plant them close together with lots of varieties in hopes of getting lots of crosses. In my crossed plants, it seems (where a cross happened) just 1 or 2 of the seeds in a group out of maybe 15 seeds turned out to be crossed with Moon and Stars. The other seeds might be crossed with other watermelons (or else pollinated by the same plant).

It's good to know that the stars aren't from something like mtDNA or cpDNA, though (which should normally be passed from the mother, rather than the father—the trait didn't come from the mother plants on my crosses). Some tomato variegation can be from that sort of DNA; so, that's why I mention this.