There are five commonly grown species of squash, three of these are well-known, cucurbita pepo, cucurbita maxima and cucurbita moschata, a bit lesser-known are cucurbita ficifolia and cucurbita argyrosperma.  I don’t intend to go into their history here, just know they are derived from wild species, cucurbita pepo comes from cucurbita fraterna and cucurbita texana, cucurbita maxima comes from cucurbita andreana, and so on...These forms did mix up with some other wild forms, and even between them, to come to these well-known species.  Originally the cucurbitas were probably selected for their edible grains, these are very nutricous.  The flesh of these original selection was bitter, the wild forms are still bitter-tasting, in fact, unedible.  Only later on, squash has been selected for better-tasting flesh, and nowadays the use of the hulless seeds has almost disappeared...

A very rare edible seed-pumpkin (bush form): rankenlose ölkurbis from Austria

Over the years, many selections of squash have been created, zucchinis are mostly cucurbita pepo (there are some vining cucurbita moschatas which can be eaten as zucchini as well), there are round, flat, long, thin,... forms and colours range from black to blue, green, white,...

My personnal favourite is a cucurbita pepo called sugarloaf, this one beats all other squaches.  It needs a bit more warmth to grow (and germinate), but it works outside in Belgium, give it a very good spot and you’ll have plenty! The fruits are small, the flesh isn’t thick, but it’s the finest taste ever! I only use it for stir-frying, because it’s too good to do something else with it. I like some of the hokkaido types as well, and moschata (yokohama and others) has some very good squashes too...

    sugarloaf

I intend to make a full page on seed-saving from squashes (the different species CAN cross, in contrast to what many seedsaving books say, and some good pictures to determine the difference between the species that are most commonly grown.