Quote from my old book - "A natural, tender hybrid found in Tenerife. Height 6-10 ft; spread 5-7 ft; as a short term pot plant, height 18 in., spread 12 in."
It goes on to say they need JI no 2 or to plant in the greenhouse border. Overwinter at 7-10C for February flowering. They may be stood outside from June to September but need a shady spot in the greenhouse. Water well but in winter keep just moist.
Hope this helps, it is a very old book so plants may be a bit hardier now.