Who says you can't fool Mother Nature? This is Den superbum ('Celle' x alba), growing in water culture. Since witholding water for the winter season to induce a rest period wasn't an option, we instead withheld all food and in addition put the plant outside in temps of 35-45f in full sun. After 6-8 treatments like this, the plant was apparently shocked enough for it to drop it's leaves. We resumed feeding as soon as the buds appeared.