The Rose of Castile plant provides the perfect shady spot for a wino to take a nap in after a drinking binge. That's one good reason for it to be all over the place in this novel, but there's gotta be more to it than that, right? Let's dig a little deeper.
We first hear about the Rose of Castile near the beginning of the novel, when Danny inherits his houses: "Danny and Pilon stood in front of the paintless picket fence and looked with admiration at the property, a low house streaked with old whitewash, uncurtained windows blank and blind. But a great pink rose of Castile was on the porch, and grandfather geraniums grew among the weeds in the front yard" (2.2).
Sounds kind of nice, right?
The house Pilon takes as a renter has its own Rose of Castile (3.1), too. While the houses themselves are unkempt and kind of dumpy, the plants, in particular the rose of Castile, give it a little bit of life. With the splash of color, the houses suddenly don't like quite so sad and boring. In fact, the Rose of Castile is doing what later Danny and his friends will do themselves: like them, it brings the sad old place to life.
And it's not just the house that is brought to life. When the friends are at their happiest and their partying reaches its peak, the rose of Castile shows up again: "The sun glistened in the pine needles. The earth smelled dry and good. The rose of Castile perfumed the world with its flowers. This was one of the best of times for the friends of Danny" (14.12).
Sure, Danny and his friends are trying to make the most out of a drab old house, but they're also trying to make the most out of lives that are drab and kind of going nowhere. The Rose of Castile, you could say, is like the visual manifestation of these guys' efforts to make their lives a little better and a little more interesting.
A Rose by Any Other Name...
There's no denying that this plant has one funky name. Did you think it was a rose? We sure did.
We were so wrong. As it turns out, the Rose of Castile isn't a rose at all: it's a kind of flowering shrub or tree called a fuchsia. Most people these days do call this plant a fuchsia, but you can also call it a Rose of Castile or a Damask rose.
So why would Steinbeck choose one of these names over the others? Well, Castile is a region in Spain, which is where Steinbeck says the paisanos claim to be from. So maybe the Rose of Castile is meant to represent their heritage.
Still, there's something a little ironic about giving the fuchsia plant such a grand name, and maybe Steinbeck is poking gentle fun at the paisanos here, since they're Californians more than anything else. They're not Mexican, not Native American, and not pureblood Spanish. They're the colorful people who populate the novel, they bring the impoverished Tortilla Flat some beauty, and they go by a name that doesn't quite fit them but is their name nonetheless.