We usually think of lush tropical gardens when Hawaii comes to mind, but much of our land — especially on the leeward side — is desert.
There are, however, many delectable fruits that actually do best where conditions are hot and dry. Figs, pomegranates, papaya and dates are just a few that come to mind, but mangoes are by far the most popular.
Mango trees will grow almost anywhere on the island, from sea level to 2,500 feet elevation, but where conditions are too wet the fruit is often damaged by fungal diseases. There are literally scores of varieties that can produce delicious fruit from early spring to late fall.
If you already have one or more mango trees in your garden, you might have noticed some things that reduce the quantity or quality of your fruit. If we have wet weather when the trees begin to flower in December and January, the blossoms will abort because of one or more fungal diseases. If this happens, the trees will tend to flower again, but most commercial growers will apply a recommended fungicide to keep the flower set and get an early crop.
As the fruit matures we might have wet weather that will make ideal conditions for anthracnose, which is caused by a fungus and streaks the fruit. This also might be avoided by applying a fungicide.
The main insect that damages fruit is the mango seed borer. This causes the flesh to be mushy around the seed. Sanitation is the key by removing rotting fruit from the ground. Another cause of mushy flesh is calcium deficiency in our volcanic acid soils. Addition of dolomitic lime with the fertilizer schedule will avoid this problem. Trees can be fertilized two to three times per year with a formula low in nitrogen and high in phosphorus and potassium.
Another easy fruit for drier areas or well-drained soils in high-rainfall regions is actually not a tree but a big herbaceous plant.
Papaya plants are a natural for almost any garden. They are prolific and nutritious. Probably no other plant supplies the home gardener so much for so little effort. This tropical America plant will grow and produce fruit the year round with a minimum of care. Green, unripe papayas are high in papain that helps digestion. The leaves also are high in papain and used in cooking. Ripe fruits are high in calcium and vitamins A and C.
Start with good plants, pay proper attention to fertilizer and moisture needs and keep insects under control. You will harvest some very good fruit that will repay you for your trouble.
There are several varieties, from the big watermelon fruit to the small Solo types. Most folks prefer the bisexual, or Solo, strain of papaya. This type produces a high percentage of top quality fruit. Seeds from the large watermelon types produce male, female and bisexual trees.
Most of the male trees must be eliminated as soon as they are detected. They are identified by means of their bloom stems. These are sometimes up to more than a foot in length and have many flowers. Female blooms are produced close to the stem but have no pollen bearing stamen. Bisexual flowers have ovary and stamen, thus can self-pollinate.
Occasionally, garden shops and nurseries offer Solo papaya plants for sale, and the gardener who needs a few plants will do well to buy his plants rather than attempt to grow them from seed. For larger numbers of plants, you can grow seed from selected fruit. Seed order forms are available from the University of Hawaii Cooperative Extension Service.
The papaya is a relatively short-lived herbaceous plant, reaching a height of 15 feet or taller in five years. A top quality plant should produce more than 150 pounds in a two year period. But commercial growers often harvest up to 300 pounds from a plant during a three year period. After that, the plant becomes so tall it is difficult to pick fruit. Production drops rapidly.
Here are some tips for successful papaya production:
Select seeds from a fruit that you like or purchase UHCTAHR seed. Plant three of four seeds in individual containers, preferably those from which the plants and soil can be removed without injury to roots. Paper potting cups are OK for planting as long as they have good drainage.
When seeds begin to sprout, fertilize with a soluble fertilizer once a week, mixing according to the manufacturer’s directions. It takes six to eight weeks to raise plants large enough to set out in permanent locations.
Set plants in permanent sunny locations at least 8 feet apart. The area should receive as much sun as possible. Put about three plants to a hill, 1 foot apart in the hill. Keep them there until you determine the sex, and then remove the males and weak females.
If the soil in which you are to set young papaya plants is poor, prepare it two weeks ahead of planting by spreading complete garden fertilizer such as 8-8-8, 16-16-16, or 10-30-10 over a 4-square-foot area about the site of each hill and dig the fertilizer into the soil. Wet it down so the fertilizer will dissolve and mix well with the soil.
Soil also must be free of nematodes, microscopic worms that feed on papaya roots, which cause root knot damage in papaya. Good fertilization practices and mulching will minimize nematode damage.
Fertilize newly set out plants once a week with soluble fertilizer for the first month. Then begin fertilizing with a regular dry garden fertilizer, applying once a month.
The papaya requires large amounts of fertilizer for best production. Spread the fertilizer out over an area roughly covered by the leaves.
A papaya plant won’t thrive in soil that is too dry or poorly drained. Young plants must be kept well watered until they are established, then watered every four or five days during the dry season. Mulching will help to conserve moisture. In wetter areas of the island, irrigation will only be necessary during drought periods.
Pests can give papaya growers trouble. The worst pests are aphids, mites and fruit flies. There has been no insecticide that will give satisfactory control of the fruit fly in dooryard plantings. Harvesting fruit before they become over-ripe will help keep damage to a minimum. Sanitation also is important. Do not leave fruit to rot in the garden, thus allowing fruit flies and other unwanted pests to proliferate.
Mites, almost microscopic spider-like creatures, sometimes cause visual damage. This does not usually affect the taste of the fruit.
With little effort your papaya plants should reward you with abundance.
For more information about growing tropical fruit, call the Master Gardener helpline. The phone number in Kona is 322-4893. The number in East Hawaii is 981-5199. We also have a tropical fruit association that assists folks in growing fruit commercially. Meeting times and places cam be found by an easy web search or by calling the Master Gardener helpline.