Castor Bean flowers
Ricinus communis* / Euphorbia Family
I took this photo from the car window with a telephoto lens at a pull out on the highway going up to Big Bear Lake because it was pouring down rain (the only rain we saw on the 2 week trip). Castor bean plants are quite common in southern California. The fruits are the source of the deadly poison, ricin, so this would not be a good plant to have growing where children would have easy access to it.
Castor bean plants are non-native. The flowers are monoecious. It is easy to see the red pistillate flowers at the top of the flower stalk and the opening yellow staminate flowers below.