I am a peculiar person and sometimes I do peculiar things, and one of my favorites is to write on walls. I have the (admittedly mixed) good fortune to own a couple of rundown houses with incompletely finished interiors, and the temptation has been impossible to resist at times.
One of my casually marked inscriptions is my favorite cruciferous quote, from one of Louse Erdrich's books; "Only pull forth the nails."
On the rare occasions I have visitors, it's happened that someone has read this and asked; "WTF?"
It's a Christ reference, I respond. It's about giving yourself a break in life by taking yourself down off the cross.
Christ has had a lot of impact in botany too. Passionflowers are named as such because of a complex set of religious symbolism having to do with the various parts of the flower; see Wikipedia.
A more lowly and generally much less ornate group, the Cruciferae, also shares this distinction. They are named as such because of the four petals of the flowers of this family, also representing the Cross in question. The Cruciferae, however, lack all the extra parts and fringes and other bits and pieces ascribed to Christ's Passion that the passionflower includes. They must instead settle with being our simple cabbages and mustards, our Brassica species that have shown some solid evidence of helping keep us safe from some cancers, when we eat enough of them, however much that may be.
Well, good for them! And there's a lot of them, and they're rather intertwined in some cases. A rutabega, for example, is the result of crossing a cabbage and a turnip. Arugula (or rocket) is Eruca sativa, and not a Brassica species at all, which is awfully confusing considering that its leaves are hot like mustard leaves, its flowers look like mustard flowers, and it's generally a mustardy sort of plant critter, much more so than all those broccoli and turnips & cabbage.
But; who are we to question the vagaries of taxonomists? Brussel sprouts, kale, these are Brassicas too, also not looking all that much like mustard, especially some of those frilly-leaved kales. Poor arugula; left out of the crowd.
A whole bunch of these puppies are Brassica oleraceae. To give you a sense of the extent of the manic efforts of plant breeders; here's at least a partial list:
Broccoli, brussel sprouts, cauliflower, green cabbage (the light green head cabbage), red cabbage, savoy cabbage, (chinese cabbage is Brassica rapa), collards, kale, and kohlrabi.
Watercress is in the same family, but is from what I gather in the genus Nasturtium, which has nothing whatsoever to do with the flowers you grow in your garden you call nasturtiums (and yes, I too have at times come to hate all nomenclature of living things and wondered if it weren't better if we might all just call individual members "Harry" or something.)
Meanwhile, I note that Wikipedia is calling all of this the Brassicaceae; not the Cruciferae. Like I said.
I can understand that. There's an awful lot of these plants in the genus Brassica. But I think I'd rather miss the Cruciferae; and I'm not sure I'm quite willing to give it up on such short notice.
Now your leaf and seed mustards, which apparently haven't been so intricately interbred, involve a variety of Brassica species.
Leaf mustard - Brassica juncea
Other mustards (I think these are seed mustards)
Brassica nigra - Black mustard
Brassica hirta - Burgonde, French Brown, Tilney, white mustard.
Radishes are Raphanus sativus - at last, something not in Brassica! But there's no mistaking them for anything other than a Crucifer -- err, Brassicacer?
Rutabegas are Brassica napus, which is apparently how the taxonomists got around this misogenation between the cabbage (B. oleraceae) and the turnips (Brassica rapa, same species as Chinese cabbage; and I know, I know - why on earth not "B. Rapaceae? )
Now, you might ask; how do you grow any of this? Well, your humble desert grower here has had mixed experience with these, but we will note that London rocket, Sisymbrium irio, can get impressively invasive down here in Carlsbad during wet winters. It gets itself started in November or so, and with a lot of rain, one can wind up with a veritable London rocket lawn quite effortlessly.
However, that doesn't happen too often apparently, and I only had the opportunity to have one once, several years ago. This stuff looks like mustard except with lousy flowers. It makes great compost, and probably wonderful fodder for a variety of creatures. It also tells us that the Brassiculars like it wet and on the cold side, so keep that in mind. Don't underestimate them. I've had broccoli just cringe up in 15oF nights here and then be all bright and happy a few days later.
I think a lot of our American vegetable food crop Brassiculars come from California, which suggests you can grow them in the desert and thus in alkaline soil, but if you grow them in the desert when the sun is getting happy they will equally happily go to seed. Plant 'em in the fall, start early. August might not be a bad idea. I don't plant in August a lot down here because it never gets quite cool enough. But an interesting idea might be to have some kind of shaded open greenhouse to start them in.
Of course, the problem with that is that if you've got anything like that sort of space around in the late hot desert summer, it's likely to be pretty premium space and in high demand. I gotta say; anyone who moves out to this part of the country? I advise you; figure out how to make shade and start early. Be inventive, think about planting in containers, think about fast growing, drought-tolerant trees with big heavy leaves. And then, think about how to grow stuff that keeps people from getting cancer. I can't think of a better niche market.