Sure that's not a form of D. natalensis?
I have some plants grown from seed labelled as D. madagascariensis from Mpumalanga that look very much like this plant.
You keep it dry. Bone dry.
For more control I'd place it in a ziplock bag in a cool place indoors and let it do what it wants. When it begins to grow repot and water. If you're lucky it'll hold back until next autumn.