A   B O U N T I F U L   G A R D E N

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Going Bananas in the Desert

by Dick Gross,
Master Gardener

Banana trees may not be plentiful in Phoenix and surrounding areas, but if you take the time to look you will occasionally notice their broad leaves peeking over a back fence or adorning a sheltered enclave in a front yard. Most of these banana plants will be of unknown or unnamed varieties, grown more for their appearance than anything else. For the sake of this discussion, however, it can also be assumed that many of their titled cousins, the varieties you see in local supermarkets, will flourish here as well.

Temperatures over 100 degrees and the occasional frost can take their toll, but with a little luck and a bit of acquired know-how you can raise banana plants successfully here. You can enjoy the sight of their beautiful, tropical leaves growing next to your saguaros and palms and, better still, you can treat yourself to a banana split made with your own homegrown bananas.


DESCRIPTION
The banana is not a tree, but an herb. Julian W. Sauls, Extension Horticulturist with the Texas A&M University Agricultural Extension Service, describes it as a tropical, herbaceous plant consisting of an underground corm and a trunk (pseudostem) comprised of concentric layers of leaf sheaths. A true stem, with a terminal inflorescence (flower) that bears fruit, is the last thing to emerge from the center of the pseudostem. The flowers appear in groups called "hands" along this true stem. They are covered by purplish bracts, which roll back and shed as the fruit stem develops. Generally, a bract rolls up and sheds to expose a new hand of flowers almost daily.

PROPAGATION AND GROWTH
A single banana pseudostem will live only 2 to 3 years, or until its fruit is harvested and it is cut down. But the corm from which it grew can survive for many years, and every one of the dozens of pups it produces has the potential to develop a stalk of bananas. The corm will continue to enlarge and store energy to nurture an endless supply of pups.

To harvest the pups for purposes of starting new plants, allow them to reach about 2 feet in height and then sever them from the mother corm by inserting a sharp, clean 12-inch to 15-inch narrow shovel to its full depth vertically all the way around the pup's stem. Worry the base out while inflicting as little trauma as possible, and wash off all the soil. To conserve moisture in the corm, lop off all the leaves about 2 inches above the tip of the stem. If a pup has no roots at all, it probably won't survive. Toss it. Even if there are roots they won't survive the trauma. Cut them off close to their point of emergence from the corm, and new roots will grow from dormant eyes at the right time. Let all wounds scab off in full shade for several days before planting at the same depth. Keep the soil on the dry side until active new growth appears.

Although you should grow banana plants in full sun, even in the summer, shade can be an important factor where young transplants are concerned. Normally, new shoots arising naturally from underground buds in an established corm receive nourishment from the corm during their first few months of existence. During this period the other members growing from the same mat provide necessary shade. However when you sever a young plant from its mother and plant it with its few roots cut off, you must be prepared to provide shelter and water until it can grow new roots, adapt to the new environment, and eventually build a colony of its own.


Strong winds tend to shred the leaves of bananas, but the green tatters will still photosynthesize and manufacture food. You should keep each individual leaf attached to the plant until at least two-thirds of it has turned brown. The unattractive dead leaves don't need to be removed after that, but if you wish to do so for cosmetic purposes you can shred or chop them up and layer the debris around the base for mulch.

A single banana pseudostem has a short lifespan, producing one stalk of bananas in about 18 months in ideal soil and climate conditions. In a less-than-perfect environment, however, you may have to wait 2 years or longer to sink your teeth into your own homegrown, tree-ripened banana.

Banana plants multiply rapidly. One plant will form a grove in 2 or 3 years, and will need to be restrained to remain attractive.

FLOWERING AND FRUITING
Bananas frequently bloom in Phoenix, but fruit is often stunted and limited to 3 or 4 hands with rather bland flavor. Tasty fruit can be produced here, however.

Poor fruit quality may be a function of genetics, but more likely it is the result of nutrient deficiency and inadequate water. Quality can also suffer when the flowering stem is engulfed in a dense banana grove, or grows in close proximity to other hungry, thirsty vegetation. Fruiting exacts a large energy toll from the corm, requiring a lot of food and water to sustain it. Competition for the available nutrients is not helpful. Fertilizers high in potassium (K) are recommended to enhance quality, and are evidently a part of a healthy banana's diet.

Strictly speaking, there is there is no such thing as one "banana plant" in nature. Multiple stems emerge from a corm that continually enlarges and sends up new shoots. With adequate food and water, you will always have a "herd," ranging in size from large to small, popping through the soil. To get the best and most fruit, especially under less than ideal conditions, you should limit the population of any group to three stems, staggered in size. You will need one adult (that will be chopped down to a 2-foot stub after the stalk of bananas is harvested), one juvenile, and a baby. Remove all other growth.

You can sever suckers at their base as soon as possible after emergence. Scoop out a hollow and fill the cavity with kerosene to kill the bud that will otherwise continue to grow and consume energy. After the inflorescence has emerged, lop off the flower head as soon as the hands fail to set. The immature, tiny fruits will fall off naturally. Bananas are believed to flower only after a certain number of leaves have been produced. Guesstimates run to 60 leaves, but the number of months it takes to reach the magic number depends upon the plant's immediate environment. You can count them if you really wish to satisfy your curiosity.

After a stalk of bananas has developed, it may be 5 to 7 months before the fruit is mature and ready to pick. During this period you can protect the stalk from the direct summer sun by covering it loosely with a reflective lightweight material such as an old T-shirt. Harvest by cutting the stalk at the yoke when the ribs on the bananas have practically disappeared and have the appearance of a supermarket banana. Hang in a dark sheltered spot to ripen, or leave it protected on the plant. Pick a "hand" at a time, as desired, and let it ripen on the kitchen counter like any other banana.

WATERING
The banana needs well-drained, rich organic soil. In warm weather the plant needs plenty of water, but during the winter months when morning temperatures drop to about 55 degrees Fahrenheit, growth virtually shuts down and very little moisture is required. During this time the soil around the plant should be damp, but irrigate only enough to keep it that way. When thirsty, banana leaves tend to fold together to conserve moisture. If you study them, you will soon learn their sign language.

Before planting your banana, you should test the soil's ability to drain. Dig a post-size hole about 2 feet deep and fill it with water. If it empties within 2 hours, the drainage is ideal. It is very important to note that there is a danger of overwatering once a banana plant has been put in the ground. If you irrigate a banana to the extent that the soil becomes saturated, the roots won't get air and rot will set in. Learn to adjust the irrigation frequency to the rate at which the water permeates through and out of the root zone with a flushing action. Wet feet can kill bananas any time of the year, but winter is a particularly crucial period; water should not be added until the soil is quite dry during these months. This herb is susceptible to diseases associated with cool, wet, soggy soil. (Our climate does not appear to harbor numerous other diseases that tend to plague the banana in the tropics).

Banana feeder roots can reach as far away from the pseudostem as the tips of the leaves extend outward. A common tendency is to irrigate in a basin tightly encircling the corm, but under those conditions the plant often languishes from malnutrition. Roots will not penetrate into dry soil, and a restricted root system will retard every other feature of the banana plant. So if at all possible, water deeply and feed to the edges of leaves and just beyond.

FERTILIZATION
It is often said that an old compost pit is the perfect spot to plant a banana; however, you would still have to fertilize the plant. Bananas can be fed by foliar application weekly with a balanced, soluble fertilizer. Apply by drenching the leaves on both sides during a cool part of the day. It is better to provide frequent light feedings to these herbs only when actively growing, than to supply sporadic, heavy doses of nitrogen that is quickly leached away.

During the active growing season, apply 1/4 cup of ammonium sulfate every 2 weeks on non-fruiting plant groups, and 1/4 cup weekly on fruiting plants. Blend the dry fertilizer into damp soil in a shallow trench at least 18 inches from the clump, and water it in until a probe can be easily inserted 18 inches into the ground. Do not fertilize bananas when the morning temperature drops below 55 degrees. In cold weather, growth has virtually shut down and they cannot use the additional nutrient.

FROST PROTECTION
The average mild Phoenix frost of moderate duration will never kill the corm and roots, but the tender leaves will freeze readily unless they can be covered or otherwise protected. The length of the freeze is often forecast. That information is critical to determine the extent of protection you put in place. One hour at 32 degrees Fahrenheit may inflict minor injury; three hours at 33 degrees could kill every tender thing in your yard.

The shock suffered from losing its foliage will delay fruiting and set the development of a banana back several weeks, thus making the energy you spend saving it a worthwhile effort. Assume that this winter will bring a frost and prepare for it in advance. Depending on the frost severity expected, one or all of the following protective measures can be used if the plants are too tall to be simply covered with a sheet or frost cloth.

First, remove any heavy mulch from the basin until needed again for preserving moisture. You can plug in an air fan and direct the air into the leaves. Use one with the largest volume output you can find. An industrial oscillating fan on a stand works great. You can protect stems by wrapping them with old jackets or blankets. You can drape Christmas tree lights on the leaves, or place floodlight or other heat source underneath. Remember to use electrical devices with caution.

In summary, you should grow bananas in full sun in well-drained soil rich in organic material. Water and feed them well during warm weather, let the plants rest during the winter, and protect them from the 2 or 3 mild frosts that occur each year. After that, you can mount a sign in your front yard that reads: TROPICAL FRUIT GROWN HERE.



Maricopa County Master Gardener Volunteer Information
Last Updated January 23, 2004
Author: Lucy K. Bradley, Extension Agent Urban Horticulture, University of Arizona Cooperative Extension, Maricopa County
© 1997 The University of Arizona, College of Agriculture and Life Sciences, Cooperative Extension in Maricopa County
Comments to Maricopa-hort@ag.arizona.edu 4341 E. Broadway Road, Phoenix, AZ 85040,
Voice: (602) 470-8086 ext. 301, Fax (602) 470-8092