I have a bunch of banana trees in a greenhouse that are turning brown. Some are totally brown and others are turning brown at the ends of the leaves. The trees are about 10 feet tall. Any idea why they are turning brown and what can I do to fix them?
Are you growing Musa basjoo, Musa ensete, or another species of banana? Also, I wonder if your greenhouse is heated or not. Here is a link to comments on growing Musa basjoo outdoors in the Northwest on the University of British Columbia Botanical Garden Forums.
According to this site, leaves which have browned from the cold can simply be removed in the spring. Here is a link to another discussion of browned banana leaves, from Houzz’s Forum.
Since your plants are under cover, there are probably different issues to consider, such as the humidity and temperature level in the greenhouse, and the amount of water the trees receive. They need to be kept moist but not waterlogged. Here is a link to general cultural information from California Rare Fruit Growers.
According to the book Exotic Gardening in Cool Climates by Myles Challis (Fourth Estate, 1994), Musa ensete [now referred to as Ensete ventricosum] is best overwintered in a greenhouse. It needs a large amount of water during the growing season to match the evaporation from its huge leaves, and it is a heavy feeder. Musa basjoo is the more ‘hardy’ banana. Here is what the Royal Horticultural Society (now archived) says about overwintering Musa ensete, or Ensete:
“To overwinter Ensete, our glasshouse is kept at 16C (61F) by day and 12C (53F) at night – at lower temperatures, lifted plants are prone to rotting. The lower the overwintering temperature, the earlier Ensete should be lifted and established in their winter containers, and the drier they should be kept subsequently. If only frost-free winter quarters are available, permanent container culture may be wiser. Musa species and cultivars are more forgiving of this operation, and can even be stored in a shed or garage.”
If you do not think that cultural conditions are the cause of the problem, you might look at this description of a disease affecting bananas.
Purdue University’s New Crop page has some information about diseases of banana.
You might also bring sample leaves to a Master Gardener Clinic if you suspect a disease is causing the leaf problems. For information about Clinic hours see their website (Plant Clinic Schedule).