A singular concern

Oh dear, rather a long time since I posted.  It's been a migraine/insomnia/backache sort of week, with lots of work stuffed in between the inoperable periods, so that may explain the gap.

I have plenty to post about, mostly about seeds and seed catalogs (went to a fun seed exchange yesterday, got to meet Ira Wallace and hear her speak, got all my seed orders in after collecting the freebies of which there were plenty) but today, while putting together the data that will hopefully allow me to create a coherent map for the demo garden (mapping my own garden is a luxury I will not have time for, I suspect), a linguistic puzzle occurred to me, trivial to be sure, but I'll share it anyway.

So, when we're making lists of vegetables (and other plants too, I think, but I'll stick with veggies for now), whether in a catalog or for planning purposes or whatever, why do we state some of them as singular and some as plural?

I give you some gratuitous (and singular) Swiss chard, and carry on, citing from the Southern Exposure catalog in Ira's honor, as I think their usage is completely typical.

Singular vegetables:
Cabbage
Cauliflower
Celery
Chard
Corn
Eggplant
Garlic
Kale
Kohlrabi
Lettuce
Mustard
Okra
Rhubarb
Squash
Watermelon

Gratuitous plural tomatoes

Plural vegetables:
Artichokes
Beans
Beets
Carrots
Cucumbers
Leeks
Onions
Parsnips
Peas
Peppers
Radishes
Tomatoes
Turnips

Some oddities: broccoli is an Italian plural that's treated as both singular and plural in English; collards doesn't really have a singular; Southern Exposure makes the choice to list "Muskmelon" in the singular, but I usually see "Melons" (and often "Watermelons" too).

So why these default choices?  I considered the idea that plural vegetables are those that bear multiple product on one plant, so you can't really have just one (although I have had tomato plants like that), but then one hopes to get more than one okra per plant and squash are notorious for overproducing.  You can have just one plant of cabbage or chard, but one corn plant is not good strategy.  Radishes produce one root per plant, as do all the other root vegetables in the plural list, and artichokes, if you can get them to bear at all in this climate, usually have one flower bud, but are always plural in catalogs.

Most but not all of the cabbage family plants end up on the singular list, including all the leafy ones (if you discount collards as above).  In fact leafy things are generally singular, unless you call them "greens."  Leeks and onions are always plural, but you never hear "garlics."  Eggplant, the fruiting nightshade family plant, is routinely singular (even if you call it aubergine), whereas peppers and tomatoes are always plural.

So I really have no answer other than "tradition" though I expect it could be investigated.  I can tell you that an excerpt from "Landreth's Companion for the Garden and Farm" of 1884 (conveniently provided in the fancy new catalog) gives us much the same usage except that carrot, leek, onion, pepper and tomato are singular.  I'd have to burrow around a bit to find older sources than that.

Probably I should be concerning myself with more important matters (like making the damn map) but distraction gives life savor.  Along with vegetables.  (Please ignore implied lack of verb-subject agreement.  Vegetables are usually plural, and somehow not so appealing when not.)