[UPDATED 2/19/13: added a few more comparisons, and by popular request, appended the list of non-a produce from WordNet.]

On Facebook today, I saw several people referring to a meme "Name a fruit or vegetable that does not contain the letter 'a'." with the comment "not that easy" above it. My immediate thought was that this was silly. Lots of non-a words occurred to me (cherry, lime, plum, beet, celery, turnip, etc., etc.)

But easy or not, the implication behind the challenge is that fruits and vegetables have the letter a so often that counterexamples are hard to think of. That's a testable proposition. We want to know what percentage of English terms for fruits and vegetables contain an a, and how that compares to the overall percentage of nouns with a. In other words, is searching for a non-a item of produce any more difficult than searching for a non-a noun in general.

I wrote a quick Python script to find all the produce (fruits and vegetables) in WordNet* and count how many contained an a compared to the overall frequency of a-containing words. [UPDATE] I also checked a couple of other categories to see how produce compared with medicine names and (non-human) animals. Here are the results:

Type	Has-A	No-A	Total	%-A
Fruits/Vegetables	410	196	606	67.7%
Medicine	726	323	1049	69.2%
Animals	5290	2113	7403	71.5%
All Nouns	80700	37098	117798	68.5%
All Lemmas	97360	49946	147306	66.1%

So not quite 68% of produce terms in English contain the letter a, a clear majority, but essentially identical to the proportion of all English nouns with an a. It should be no harder to find a non-a containing produce term than a non-a containing noun of any other type. Nothing to see here. Move along.

* I counted as a fruit/vegetable any noun that had one of the following synsets in its hypernym path: produce.n.01, edible_fruit.n.01, vegetable.n.01, vegetable.n.02.

[UPDATE: Appendix]
Here are all the non-a-containing produce terms identified as such in WordNet. You may thing that some of these terms are "cheating." For example, it contains variant spellings, specific varietal terms for types of fruit where the generic term does have an a, and a few processed foods (e.g., french fries). But I'm not going to skew the list by imposing my own judgment, and the a-containing terms have a similar spread of terms, so I don't think their inclusion really affects the overall percentages, although you may get complaints if you try to use them in response to this question.

beet	beet green	beetroot	bell pepper
berry	bibb lettuce	bilberry	bing cherry
blueberry	bok choi	bok choy	bosc
boston lettuce	boxberry	boysenberry	broccoli
brussels sprouts	buttercrunch	celery	celery root
celtuce	checkerberry	cherry	chicory
chile	chili	chili pepper	chilli
chilly	chinese celery	chinese gooseberry	chinese jujube
chipotle	chips	chop-suey greens	chou
citron	citrous fruit	citrus	citrus fruit
clementine	cling	clingstone	coco plum
cocozelle	cole	common beet	common sorrel
cos	cos lettuce	coss	courgette
cowberry	cress	crookneck	cucumber
cuke	curly endive	delicious	dewberry
dried fruit	edible fruit	eggfruit	elderberry
emperor	empire	endive	fennel
fig	finocchio	florence fennel	fordhooks
freestone	french endive	french fries	french sorrel
fries	frijole	genip	gherkin
globe pepper	golden delicious	gooseberry	green
green goods	green groceries	green onion	green pepper
greens	grimes' golden	gumbo	hog plum
home fries	honeydew	honeydew melon	hot pepper
huckleberry	iceberg	iceberg lettuce	jujube
julienne	juneberry	kentucky wonder	key lime
kiwi	kiwi fruit	leechee	leek
legume	lemon	lentil	lettuce
lichee	lichi	lime	lingonberry
litchee	litchi	litchi nut	lychee
mcintosh	melon	mombin	morello
mulberry	murphy	mushroom	muskmelon
net melon	netted melon	newtown wonder	northern spy
nutmeg melon	onion	pepper	persimmon
pigweed	pimento	pimiento	pippin
plum	plumcot	pomelo	potherb
produce	prune	pulse	pumpkin
purple onion	quince	red delicious	red onion
red pepper	ribier	scuppernong	seckel
serviceberry	sloe	sorb	sorrel
sour cherry	sour gourd	soursop	soy
spiceberry	spring onion	sprout	spud
summer crookneck	sunchoke	swede	swedish turnip
sweet cherry	sweet cup	sweet melon	sweet pepper
sweetsop	thompson seedless	truffle	turnip
turnip greens	ugli	ugli fruit	veg
veggie	white turnip	whortleberry	wild plum
winter cress	winter melon	wintergreen	witloof
yellow delicious	yellow mombin	yellow turnip	zucchini