The melons, members of the gourd family
, can be divided into two sub
s and watermelon
s. The muskmelons
can be further subdivide
d into rough
-skinned and smooth
The rough-skinned muskmelons include the cantaloupe, yellow on the outside and orange on the inside, and the Persian, a larger, grey-green melon. The smooth-skinned varieties include the honeydew of cream-colored shell and green flesh; the large, yellow-rinded Crenshaw, and the pale yellow Casaba.
Watermelons, actually a relative of the cucumber, are usually green on the outside and deep red on the inside. They can range in weight from a mere 5-pound spheroid to well over 100 pounds. Certain "seedless" varieties exist; these are not truly seedless, but contain small white undeveloped seeds instead of the inedible black seeds of the "normal" melon.
Melons tend to be at their peak in late summer and early fall. Watermelons start to get good in June and tend to stop in September in most places. Locally grown cantaloupes can be found starting in early July. Honeydews can be found from July to October, overlapping the August-September season of the Crenshaw and the September-October availability of the casaba.
In general: They should smell sweet, but if you're standing in front of a tableful, it's hard to tell if the individual melon in your hand is the one with the lovely fragrance. The other myth is that the blossom end will be soft in a ripe melon; however, everyone before you has heard the same thing and an unripe melon may have a soft spot from all those people pushing it to test.
Cantaloupes: When locally grown, look under the webbing for orange to yellow-orange color. If not local, just make sure they're not squishy.
Honeydew: The color is the most important; they should be yellow to yellowish-green. The skin should be relatively smooth, and shouldn't be spotty.
Casabas and Crenshaws: should have no green showing. Since the Crenshaw is usually sold in halves, you should be able to just tell by looking at the flesh (which should be pale pink].
Watermelons: are tricky. Some people will tell you that they shouldn't have stems, or the stems should be dried. These people are wrong. Not that you should run out and buy only watermelons with stems attached, but it's just not a reliable method. People also tell you to avoid those with yellow bottoms. This is just a result of its being on the ground while it's growing. The most reliable method is to thump FIRMLY on the rind; it should sound just barely hollow. Too hollow means it's green; too dull means it's overripe. Got that?
I said it was tricky...
Cantaloupes will ripen if bought green; if so, store them at room temperature until they're orange. Afterwards, they'll keep in the refrigerator for about a week, preferably wrapped so as not to absorb odors.
Casabas and Crenshaws will also ripen in the open, provided they are whole. Honeydews should immediately go in the fridge. Watermelons can be left out for a few days in a cool, reasonably dark area if whole and refrigerated if cut. (For that matter, any cut melon should be refrigerated.) Watermelon also freezes well in chunks; those chunks can be later pureed into slush which is nice in the summer.
Invaluable help provided by LadySun
and by Irena Chalmers' The Great Food Almanac