The seeds contain ricin. Pretty easy to cut off the seed pods before something/one eats them.

The seeds sprout fast.
I'm trying to get some going this spring.

... a castor "tree" at San Antonio Botanical Gardens.

If your garden is a mass of green, these purple leaves offer great relief.

Thanks for the photos!

I can't think of what the advantage would be to "winter sowing" these seeds. You'd have lowered germination due to winter cold and wet, plus the possibility of dead seedlings if there's a late hard frost. Much better to direct sow after the safe planting date or start indoors 3 weeks or so before setting plants out (fast growers don't need a lot of lead time).