Ampalaya (Momordica charantia) is a vine with delicate, lacy-looking foliage that produces unusual melons. The melons resemble warty cucumbers when young but turn orange and split open when they mature. Bitter melon, balsam pear and bitter cucumber are a few of its common names. It is a perennial plant in U.S. Department of Agriculture plant hardiness zones 10 and 11. In all other climates, it is grown as an annual, just like other types of melons, gourds and cucumbers.
Start the ampalaya seeds indoors three to four weeks prior to the last expected spring frost to give them the longest growing season possible. Pour soil-based potting soil into 4-inch-diameter peat pots. Moisten the potting soil with water. Plant one seed 1/2 inch deep in each peat pot. Put the planted peat pots in clear plastic bags and seal them. Set them in bright, indirect light in a room where the temperature is about 70 degrees Fahrenheit. Water the seeds if the top of the soil begins to dry. They should germinate within ten days.
Select a full-sun planting site where the ampalaya will be exposed to at least six hours of direct sunlight each day. The planting site must be large enough to allow for 5 feet of space for each hill. Spread compost, aged manure and sphagnum peat moss over the planting site to a depth of 3 to 6 inches. Mix the soil amendments into the soil thoroughly with a dirt shovel or tiller.
Test the soil pH. Ampalaya vines grow best in soil with a pH between 6 and 6.8. Mix iron sulfate or lime into the soil to raise or lower the pH, if necessary. The application rate will vary depending on how much the pH must be adjusted and soil type.
Dig 1 1/2-foot-deep holes where the ampalaya will be planted right after the last expected hard frost. Space the holes 4 to 5 feet apart. Pour 1/4 cup of bone meal into the hole. Fill the hole back in and construct a 6-inch-high, 2-foot-wide mound above the hole. Pour 1 to 2 gallons of water over the mound to settle the soil.
Plant three ampalaya seedlings per mound four weeks after the last expected frost. Leave them in their peat pots and plant them so the potting soil is at about the same level as the garden soil. Space them evenly around the outer edge of the mound.
Install a 6-foot-high trellis for the ampalaya vines to climb up, or grow them along a fence. Water them once a week with 2 to 3 gallons of water poured around the outer edge of the mound. Sprinkle 1 tablespoon of 33-0-0 fertilizer around the base of each mound one week after the vines begin to bloom and again three weeks later. Water the fertilizer into the soil. Harvest the ampalayas one to two weeks after the vine blooms before they ripen and turn orange.