Growing Bittermelon

By H. Dale Sato

Some people love it; others can’t bear the taste of it, despite its health benefits.

I’m talking about bitter melon — the green vegetable Okinawans refer to as göyä. In Japanese, bitter melon is known as nigauri. Its scientific name is Momordica charantia. In Hawai‘i, it is an especially popular vegetable among older Okinawans, and is credited with contributing to the longevity many Okinawans enjoy.

Bitter melon is used in many Asian dishes: Okinawans make göyä champuru, stir-frying it with belly pork or Spam or tuna, töfu and egg; Chinese people stuff it with pork hash; and Filipinos use it in their adobo. Some Filipinos also cook the leaves. Other preparations include baking, steaming or pickling.

There are generally two types of bitter melon. The Chinese variety, which tends to be bitter, is smooth and has longitudinal ridges, while the Indian variety has “delicate spines” and is much more bitter. A somewhat different weedy type, known as Momordica charantis var. abbreviate, can be found growing along roadsides and is often harvested by local Filipinos.

The bitter taste is like that of a not-yet-ripe grapefruit or very dark chocolate. It can be traced to the quinine content within the plant. The bitterness can be reduced by blanching the bitter melon slices in boiling water for two to three minutes, or try salting the sliced pieces for about an hour and squeezing out the liquid. The riper fruits are also less bitter as are those whitish or lighter green in color.

There are many varieties of the Chinese bitter melon. Seeds are available locally at Fukuda Seed Store, Don Quijote and Koolau Farmers. Different varieties are also available at Kitazawa Seed Company and Evergreen Seeds. Unfortunately, seedlings are rarely available at local nurseries and garden centers.

Another alternative is to harvest seeds from a good fruiting plant. Seed variation can occur if different types of bitter melon are grown in close proximity to each other.
A fully mature fruit will oftentimes turn yellow and begin to split, showing the red arils and even the seeds. Remove the seeds from the arils and air-dry them. If you process the seeds and store them properly, they can last a year or two.

Select a site with abundant sunlight and good-draining soil for your bitter melon plant. The soil should have a pH of 5.5 to 7.2. Add 3 to 5 inches of well-rotted organic matter and a handful of bone meal and mix it into the top 6 to 12 inches of soil. For conventional soil preparation, add organic material along with a fertilizer like 10-30-10 or super phosphate mixed well into the top 6 to 8 inches.

Bitter melon plants can also be grown in containers that are between 5 and 15 gallons — the larger the container, the more productive the plant.

Seeds should be planted about 1 inch deep and spaced about a foot apart. Thin to 2 to 3 feet apart. Seedlings can also be planted 2 to 3 feet apart.

You should fertilize the plant every three to four weeks using such fertilizers as 10-20-20, 10-5-20 or 16-16-16, or a similar analysis fertilizer. If you do organic gardening, a fertilizer like 8-8-8 can be applied every two to four weeks. Applying products such as H-B 101, worm castings or compost tea are also helpful for organic culture.

I advise frequent watering for hot and dry climates. Feel the upper 1 to 2 inches of the soil. If it feels dry or looks light-colored, water the soil thoroughly.

Bitter melon vines will grow 10 to 15 feet long, so I suggest that you grow it on some type of trellis, be it a fence, a table or a hoop trellis. Trellising the vine ensures long and straight fruits. An ideal fence trellis is about 5 feet tall; a good hoop trellis should be 6 to 7 feet tall, which will make it easier to walk under the vines to harvest the fruits. If you are growing bitter melon in a container, consider using a tall tomato trellis or an extendable vertical trellis.

The short, warty fruit type doesn’t require a trellis — you can let it crawl on the ground or even over small plants. However, in order to contain the growth of a bitter melon vine, you should probably prune it after the first female fruits.

Yellow-colored flowers should begin forming 45 to 60 days after initial planting of the seed — male flowers first, and then a few days to two to three weeks later, female flowers with a swollen base. Male flowers will open in the morning and fall off in the afternoon.

Honeybees are the primary pollinators of bitter melon flowers. The fruits usually reach the harvestable stage about seven to 10 days after pollination.

I suggest you harvest the fruits according to your tastes. If you are eating bitter melon for the first time, you might want to harvest the fruit when it is a bit more mature, as it won’t be as bitter.

Overly mature fruits may contain the red-fleshed part called the aril, which can split in storage. The fruits need to be harvested every two to three days. Frequent harvesting will promote higher fruit production. The harvested fruits can then be placed in plastic bags or wrapped in paper and refrigerated for three to five days.

Shoot tips 6 to 8 inches in length can be harvested when the plants begin to flower and soon thereafter. The harvested tips are bundled, wrapped in paper and stored in the refrigerator.

The most common pest problem you are likely to encounter when growing bitter melon is the melon fly, which “stings” the fruits, causing premature discoloring. The sting can also affect the shape of the fruit and, in some cases, cause the fruit to rot.

The best and easiest way to protect the fruit from melon flies is to package it soon after the female flowers have pollinated. Fold a piece of newspaper to 3-by-14 inches and cover the pollinated fruit like a sleeve. Secure it with a toothpick or a bamboo skewer 3 to 4 inches long and leave the bottom end of the paper sleeve open. Adjust the newspaper size accordingly for larger and longer fruits. There are other ways to avoid fruit fly infestation, such as pheromone traps or GF-120 fruit fly bait.

In terms of diseases, powdery mildew is a common one affecting bitter melon. That’s why it’s important to plant bitter melon in an area with good air circulation and sunlight and avoid evening watering. Also, dispose of infected leaves immediately.

If you develop the powdery mildew, sulfur and bicarbonates are approved organic pesticides that can be applied to minimize the problem. For root knot nematode problems, consider crop rotation, fallowing, soil solarization or planting a green manure crop such as Sunn hemp to reduce the nematode population.

Bitter melon plants are most productive during their first six months, although it will give fruit for over a year.

If the thought of bitter melon’s bitter taste makes you cringe, consider this bit of information from the National Bitter Melon Council: Bitter melon is rich in iron and has “twice the beta carotene of broccoli, twice the calcium of spinach, twice the potassium of bananas, and contain[s] Vitamins A, C, B1 to B3, Phosphorus.” It is also a good source of dietary fiber. Maybe it’s a taste you can acquire over time.

H. Dale Sato has worked in the field of horticulture for over 50 years. As a teenager, he operated his family farm in Pähoa on the Big Island of Hawai‘i. Sato retired from a 30-year career as an extension educator with the University of Hawai‘i’s College of Tropical Agriculture and Human Resources, but remains involved in horticultural research and educational activities.