smeash

Instead of ground cover you may want to consider heavily mulching with grass cliippings, wood chips, straw etc. They add organic material and retain moisture, which bananas need. Bananas are extremely heavy feeders, so nutrients may be taken from other plants. Shade that the bananas put off can be another issue for companion plants. If you really want to grow a companion crop, i would focus on vining varieties like cucumber, melons, etc. They can be planted far enough away from the banana to get their own sun and nutrients, but can be trained to sprawl in the general area of your nana patch.