Impatiens grandis is a native to India and Sri Lanka. It flowers in the winter and a flower here and there through out the year. I would think semi-shade would be to its liking. What are the temps like? It likes to be around 75f with a good amound of humidity. I have grown it outside under part shade and it lived, it grew a couple of flower buds but only one opened. Are you growing it in a pot or the ground? You might have good luck in a pot. I have 3 different clones of it, all in pots and all doing well though one is getting yellow leaves from being to dry. This one is a clumping form which may be hookeriana which is said to be the same as grandis. Out of flower the plants look different but flowers are similar when in bloom.
I would give it morning sun, it can take a good amount of sun, and grow it in a pot with tasty compost mix. It does not like cold temps close to freezing. It will survive 40f but all the flower buds will drop. It also make a good greenhouse plant. It is also a very rare plant in cultivation and may be endangered in the wild.
Hope this helps

Thanks Mr Impatiens. Our temperature range is currently around 75 to 90 degrees, with considerable humidity. It is currently in the ground, and by your description of yellowing leaves, I suspect it may have been a little on the dry side, growing under a fairly large leopard tree.