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When looking at either the fruit, or the plant of either, is there a specific characteristic, or set thereof, of either group that distinguishes one from the other?

I am curious as to the classification of watermelon. I saw a listing of them with "Cucurbits", and am mostly just confusing myself with the little help Wikipedia is providing. Is there a taxonomical clarification someone could help me with to figure out how to sort watermelon, and know how the family tree works with respect to melons and squash?

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You mean beyond sweetness? – Peter Turner Mar 8 '12 at 18:45

2 Answers 2

up vote 10 down vote accepted

It's all genetic. Here is a list of the taxonomies of several common curcurbits:


  • Kingdom: Plantae
  • Phylum: Magnoliophyta
  • Class: Magnoliopsida
  • Order: Violales
  • Family: Curcurbitaceae
  • Genus: Citrullus
  • Species: lanatus


  • Kingdom: Plantae
  • Phylum: Magnoliophyta
  • Class:: Magnoliopsida
  • Order: Violales
  • Family: Curcurbitaceae
  • Genus: Curcurbita
  • Species: Pumpkin: maxima, Butternut type: moschata, Summer type: pepo

Cucumber + Melon:

  • Kingdom: Plantae
  • Phylum: Magnoliophyta
  • Class: Magnoliopsida
  • Order: Violales
  • Family: Curcurbitaceae
  • Genus: Cucumis
  • Species: Cucumber: sativus, Melon: melo

As you can see, the watermelon, squash, and melon are in the same family, But each has it's own Genus. Of course, every species of plant has its own set of characteristics. Watermelon vines are thinner and longer than squash vines, and the leaves are deeply lobed, compared with the squashes wide, flat leaves.

The fruit looks very similar when young, but when they are matured the watermelons have a dramatic decrease in starch content, and have low density flesh with extremely high moisture content, and a high level of fructose. The cucumber genus is lower in water content, but also store the energy supply as fructose rather than starch. The melons have more sugar than the cucumbers.

Notice that the ones with the higher starch ripen latest in the season, when animals need starch to build up fat for winter. The more sugary juicier fruits are ripened a little earlier, when the animals need quick energy.

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Don't forget, among probably other things, that there are other, but less common species out there, such as the following squash: Cucurbita mixta, Cucurbita ficifolia and Cucurbita ecuadoriensis. Cucurbita ficifolia is sometimes referred to as a melon or gourd (but it's actually a squash). Also, don't forget gourds, Luffas, bitter gourds and wax gourds (which some might classify as squash or melons, although I don't know that they really are either): Lagenaria siceraria, Luffa cylindrica, Luffa acutangula, Luffa operculata, Momordica charantia, and Benincasa hispida. – Shule Nov 19 at 22:35
Also, remember that although Pumpkins are usually C. maxima, sometimes you get them in other species that look and taste much like pumpkins (and are often named pumpkins). We probably don't have a real definitive definition of pumpkin to determine whether they really are pumpkins or just look-a-likes and taste-a-likes, however. – Shule Nov 19 at 22:46
@Shule Yeah feel free to go deeper with an additional answer if you wish. This is a basic guide for folks who will get lost in all the scientific names with all those less common relations. The species I named cover over 99.9% (by volume) of the squashes, melons, etc that people grow. – J. Musser Nov 19 at 22:54
I just wanted to point that out, since some people take things literally. Your answer was fine. :) – Shule Nov 20 at 7:46

The above answer is accurate. The simple gist of it is this:

There are two sensation categories involved: Flavor and Sweetness

There are two substance categories involved: Starch and Water

Listed below are the three fruits in question, by each of the above four items in the order of their volume from most to least:

  1. Cucumber: water, starch, sugar, flavor.
  2. Squash: starch, flavor, or flavor, starch, sugar, water.
  3. Melon: Flavor, water, or water, flavor, sugar but no starch
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Hi Pfero, thanks for the answer; I'm not sure I quite follow your explanation. Could you rephrase a bit? – mfg Sep 30 '12 at 23:54

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