Why Is Bitter Melon (Bitter Gourd) Bitter? Price and Grafting Technique Explained in Detail

They say good medicine tastes bitter and benefits the illness, and bitter melon is the best representative among foods. Bitter melon fruit tastes sweet-bitter, mainly used as a vegetable, and can also be candied; the ripe flesh and aril are also edible. So why is bitter melon bitter? What bitter melon grafting techniques are there? How much does bitter melon cost per jin in 2018? Details are as follows:

I. Why is bitter melon bitter?

The bitterness of bitter melon is caused by two substances. One is cucurbitacin, which is unique to cucurbit plants and mainly exists in the melon in the form of glycosides. The other substance is called elaterase. If both substances exist at the same time, bitterness appears. In fact, these are “natural pesticides” synthesized by the plant, used to resist adverse environments such as pests and diseases.

II. Bitter melon grafting techniques

Select suitable rootstock and scion varieties: choose cucurbit varieties with good affinity and strong stress resistance as rootstock. At present, Yunnan black-seeded pumpkin and local Mopan pumpkin are suitable; the scion varieties are generally local main cultivars, such as “Longdu Bitter Melon No. 1” bred by the Zigong City Agricultural Science Institute, large hemp-seed bitter melon, and local large white bitter melon are all acceptable.

1. Seed soaking treatment, preparation of nutrient soil, sowing at the right time

Seed soaking treatment: before sowing, crack the shell of the selected bitter melon seeds, taking care not to damage the seed kernel. Then soak the bitter melon and pumpkin seeds separately in warm water, immersing them in hot water at 55-60°C while stirring constantly so that the seeds are heated evenly; after 10-20 minutes, when the water temperature drops to about 30%, continue soaking. Bitter melon seeds are generally soaked for 8-10 hours, and pumpkin seeds for 8 hours, then rinse off the mucus with clean water. After soaking, scoop them out, spread them flat in a porcelain tray, cover with a double layer of wet cloth, and place them in a constant-temperature incubator at 28-32°C for germination. If there is no constant-temperature incubator, an electric blanket can be used for germination. During this period, take out the seeds and wash them 1-2 times a day to wash off the mucus and promote germination. Once the seeds germinate, they can be sown.

Preparation of nutrient soil: pumpkin sowing and seedling raising must use nutrient pots. The nutrient soil is prepared by mixing field soil that has not grown cucurbits for many years with decomposed barnyard manure or compost at a ratio of 3:1. For each cubic meter of nutrient soil, add 50 kg of decomposed human and livestock manure and 1.0 kg of superphosphate, spray with 50-fold 40% formalin solution or mix with 100 g of carbendazim or 200 g of chlorothalonil, cover with plastic film and pile for 10-15 days to allow full fermentation and disinfection, then spread out and turn over to air for 5-7 days, and fill into nutrient pots. Bitter melon sowing and seedling raising must use clean soil to prevent infection during the seedling stage.

Sowing at the right time: based on the climate characteristics of Zigong City over many years and farmers' cultivation habits, sowing before Awakening of Insects is generally preferred. If sowing and raising seedlings earlier, electric heating seedbeds or soil heating seedbeds must be used. Generally, pumpkin should be sown 3-5 days earlier than bitter melon.

2. Graft at the right time and strengthen the management of grafted seedlings: grafting can be done when the pumpkin has grown true (heart) leaves and the bitter melon seedlings have grown to one leaf and one heart. Cloudy days, windless days, and weather with relatively high humidity are most suitable for grafting. Before grafting, the seedbed should be watered appropriately. The grafting methods use the top insertion method and the needle grafting method.

For the top insertion method, first prepare two small bamboo skewers 8 cm long, 0.5 cm wide, and 0.25 cm thick, and sharpen one end of each skewer into a small slope about 1 cm long. When grafting, use a grafting blade to cut off the pumpkin true leaves, then insert the bamboo skewer obliquely at the top of the cotyledons in the same direction as the cotyledons, cut the bitter melon hypocotyl into a wedge shape, pull out the bamboo skewer inserted in the rootstock, insert the bitter melon hypocotyl into the cut surface of the pumpkin, place it as well as possible, and finally fix it with a grafting clip.

The needle grafting method is to first use a grafting blade to cut off and flatten the pumpkin true leaves, then cut off the lower hypocotyl of the bitter melon, and then use a special grafting needle with one end inserted into the bitter melon hypocotyl and the other end inserted into the top of the cotyledons of the pumpkin seedling whose true leaves have been cut off. The plane of the bitter melon seedling hypocotyl should contact and fit the plane at the top of the pumpkin seedling cotyledons as much as possible, and finally fix it with a grafting clip.

During grafting, cover while grafting. After grafting is completed, cover with black film for shading treatment. For 1-3 days after grafting, full-day shading and heat and moisture preservation are required. After that, depending on the weather, shade from 10 a.m. to 3 p.m. every day and allow light at other times; the temperature in the small arch shed should be controlled at 32°C during the day and 20°C at night, and the humidity should be controlled at about 90%. After 7 days, expose to light all day, and gradually carry out ventilation, cooling, and hardening treatment, keeping the daytime temperature at 25°C and the nighttime temperature at 15%.

III. How much does bitter melon cost per jin in 2018?