Sun is much better - you are likely to produce a taller plant too with full sun.

Hope this helps,
Maggie

Do you mean Ricinus communis or Fatsia japonica? If you mean Fatsia, half sun half shade is best.

I'll admit that I've never heard of Fatsia being called Castor Oil Plant. Was it grown from seed, or found among the shrubs at the garden center, Amb?