Helen's Hybrid banana is a cross between two varieties of high altitude bananas from the foothills of the Himalayas in the Sikkim region of India. One variety, the Chini Champa, is used as food and the other is a wild type usually referred to as the Darjeeling Banana. The report is that Helen's Hybrid could possibly be the closest thing to a cold-tolerant, edible banana that has been developed. The fruit is claimed to be sweet, yet have seeds. After the first few frosts of autumn the leaves die back. If the winter is especially cold the stalk will die back to the ground. The bulb at the base grows a new stem or two the following spring. If the winter is particularly harsh, protection in the way of a covering of dry leaves, straw or burlap may help keep it alive. In Medford, Oregon, there is a specimen that over-wintered in the garden without protection and came back beautifully to six feet the following summer. Keeping them in pots allows moving them to suitable locations and moving indoors for protection in winter. Pot size restricts growth. The bigger the pot, the bigger the plant. In the ground they can grow to be 10 to 15 feet high with 6 foot leaves. A 5 gallon pot would allow it to get about 6 to 8 feet depending on care and location. Banana plants shouldn't be allowed to dry out and should be well watered when the weather is hot. Care should be taken, especially when banana plants are kept in pots, to not over-water because this can cause the roots to rot. They need plenty of light indoors and can take full sun outdoors, but seem to do best with strong filtered light during hot weather.
They are heavy feeders, liking an application of high nitrogen, time-released fertilizer during the warm weather growing season. They tend to go dormant when the temperature drops below 45° Fand the leaves die back at about 30° F.The stalk and the bulb can take much lower temperatures if protected. As soon as the temperature goes above 50° Fthey start growing again. When grown in the house, they will continue to grow and do well in a brightly lit window area. A small plant should be grown indoors or in a heated greenhouse until it's large enough to be tried outdoors. The larger the plant, the hardier to cold it is.
To plant and grow them west of the Cascade Mountains of the Pacific NW, you will need to make a mixture containing 50% good potting soil, with 25% sand & 25% small gravel. (Never use beach sand in the soil mix)Try to plant in an area that will get morning sun but not the hot direct afternoon summer sun. I recommend using a water meter the first few years.