In web sites and other writing I constantly come across questions about whether something is a "squash or a pumpkin," or references to "true pumpkins" but with little useful information to back up the lingo. So I thought I'd take a moment to clear up some of the confusion about the many different words we use to refer to all these plants.
So what's the difference between a squash and a pumpkin? Botanically, absolutely none. Huh?
There are four species of the genus Cucurbita that we commonly refer to as pumpkins and squash (Brits, we'll get to you in a moment): C. pepo, C. maxima, C. moschata and C. argyrosperma. The first two are incredibly diverse in shape, color and texture while the third tends to have bottle-shaped fruits, usually striped, with a slightly bulbous top and swollen lower portion. Think of a grossly overweight bowling pin.
The confusion comes from the fact that all these plants come from the New World, and so English originally had no word for them. The American Indians on the other hand were very familiar with them and had as many words for them as they did languages. The first Native Americans that the early English settlers came into contact with were Algonquins, who called them askutasquash. According to the Online Etymological Dictionary, means "green things that may be eaten raw." The last part, =asquash, is the "edibles" part of the word, and the English shortened it to "squash." Which I suppose to an Algonquian speaker would sound like"dibles."
To the likely dismay of the Algonquins, the English stayed in the New World, and the Algonquian word fragment stuck, so Americans use the word "squash." However, the squash did not stay in the New World; it traveled back to the Old World, and to England among other places. And not having many Algonquins around to help them out, the inhabitants of Merrie Olde England had to find another word. So they likened the strange new food to something they did know, the "pumpion," which was an old word for a melon that they got from the French, who called them pompon. It eventually morphed (probably with or influenced by the diminutive/endearing ending -kin) into "pumpkin." And as more English came to America, now familiar with at least one variety of squash, they added their own new word to the mix. Most likely they had a round, orange variety, because in the US, the only thing that distinguishes what is called a pumpkin is a basically round shape, usually with vertical grooves, and an orange color. Never mind that there are white and green ones around too. These orange round(ish) pumpkins can be either C. pepo (mostly) or C. maxima (especially the giant pumpkins). For the rest of them, which were probably still less familiar to the newly arriving English, the term "squash" remained in use. This is not the case in England today, where "pumpkin" refers to a much broader range.
So what about "winter squash" and "summer squash?" Surely there must be some botanical distinction there?
Only sort of. C. pepo is a remarkably diverse species. Pretty much everything we call "summer squash," the generic term for squash that are picked while immature and includes what we call zucchini (Do we want to go there? We will.), yellow crookneck, etc., are varieties of C. pepo. But so are the orange pumpkins. And so are the vast majority of the decorative gourds, which are nothing more than pretty - but tasteless or bitter - varieties C. pepo. (The bottle/dipper gourds are of another genus altogether, Lageneria, and are old-world plants. Some of their fruits are also eaten immature; when mature they are incredibly bitter.)
Basically, the plants we call "winter squash" are the ones, regardless of species, which we allow to ripen and harden off, and which are more or less storable. Though out of the three species, C. pepo is the least storable, which is why you have to eat acorns and delicatas early, while you can keep a butternut or a hubbard around for months or even a year or more. The "summer squash" then, are simply varieties that we eat during the summer, while they're still immature. Some squash varieties can be eaten both ways, by the way.
When the members of the genus Cucurbita traveled to Europe, they didn't all go the same way. Some came directly to England, while others went through France. The French used the word courge for squash, and the immature ones were referred to as courgettes, which is what the English call them today. Only they also call them - or at least the variety C. pepo fastigata - "vegetable marrows." Which is just silly, but there is probably a perfectly logical explanation for it. Does anybody know?
Meanwhile, a similar variety that was now being grown (or had developed) in Italy returned to America with Italian immigrants. They called the squashes zucca (except for some which they called cucuzzi but just never mind) and their word for the immature ones was zucchini. These are the courgettes of England. The marrows are not as well known in the US, but they should be - though the English tend to grow them larger, they are at their best when about 8 inches long and light green, and are more flavorful than zucchini.
So in the end, the only clear distinction between all these varieties is their actual species. So now that I've confused you completely, here's a selection of some of the better known varieties of squash/courgette/pumpkin/marrow/zucchini according to species:
Most of these tend to have some fiber when mature, so more are eaten immature.
Most jack-o-lantern pumpkins
Most ornamental gourds
Some of the best winter squash, many with smooth, dry flesh and little or no fiber. They tend to make better pumpkin pie than most of the ones we call "pumpkins;" commercial pumpkin pie filling is actually made from Gray Hubbard.
Pink banana squash
Gray banana squash
Winter keeper squash
This includes some eminently edible squashes as well as several watery, stringy varieties.
Long Island Cheese pumpkin
Winter crookneck, Pennsylvania Dutch crookneck
These are not very popular in the US due to their stringy texture but some are not so bad if you run the cooked flesh through a food mill.