What Plant Is the Water Caltrop? An Introduction to the Plant Properties and Characteristics of the Water Caltrop
Water caltrop is relatively common in the south, but perhaps rather rare in the north. Many southerners buy some water caltrops in season to get a taste of something fresh, but northerners may not know what this is. So what plant is the water caltrop?
1. What is the water caltrop?
The water caltrop belongs to the family Trapaceae, genus Trapa. Also known as waist caltrop, water chestnut, and caltrop fruit, it is sweet in taste, cooling, and non-toxic. It is the fruit of the annual herbaceous aquatic plant water caltrop. The water caltrop has crisp skin and delicious flesh; it can be peeled and eaten after steaming or boiling, and can also be cooked into congee. Water caltrop is rich in protein, unsaturated fatty acids, and various vitamins and trace elements. It has the effects of promoting urination and lactation, quenching thirst, and relieving alcohol toxicity.
Water caltrop grows in lakes and matures around August each year. The water caltrop vine grows green leaves, and the leaf shape is rhombus-shaped, hence the fruit is called water caltrop. The stem is purplish red, and it bears bright small yellow flowers.
The water caltrop is an annual herbaceous aquatic plant, also called the “peanut in water”. Its fruit, the “water caltrop”, is a nut that hangs in the water beneath dense leaves, and it can only be seen by lifting the whole plant and turning it upside down. It matures after autumn, and the fruit becomes hard. If wild water caltrops are not picked, they gradually fall from the stem and sink to the bottom of the water, then sprout the following year.
There are many kinds of water caltrops. Cultivated ones can be as large as a matchbox, while wild ones are smaller, with the small ones only as big as a fingernail. They come in green, red, and purple. The skin is crisp and the flesh is delicious, and the taste is pleasant. They can be considered a fine fruit and can also be used as food grain. Generally they are eaten after steaming or boiling, or dried and chopped into fine pieces and cooked into congee.
2. Types of water caltrop
1. Wonton water caltrop, also called Nanhu water caltrop, is a famous product of Jiaxing, Zhejiang. It is a late-maturing variety, sown at Qingming and harvested from Qiufen to Shuangjiang. It is high quality and high yielding, sweet and glutinous in taste, with a yield of 1000-1200 jin per mu. The fruit skin is greenish white, with 40-50 fruits per jin. The shoulder horns point upward, the waist horns bend downward, and the belly of the caltrop is concave. The caltrop flesh is thick and solid, the skin is thin, and the ratio of fruit weight to flesh weight is about 1.5:1.
2. Small white water caltrop, produced in Wujiang, Suzhou, and other places in Jiangsu. It is a mid-to-late maturing variety, sown at Qingming and harvested from Bailu to Shuangjiang, with a yield of 600-1200 jin per mu. The flesh is firm and contains much starch, suitable for cooked eating. The fruit shape is relatively small, with 60-70 fruits per jin. The skin is greenish white, the shoulder horns extend slightly upward at an angle, the waist horns are slender and curved downward, and the belly is slightly raised. The ratio of fruit weight to flesh weight is about 1.4:1. The caltrop rosette is small, the stems and vines are tough, the growth vigor is strong, and the resistance to wind and waves is relatively strong. It has a relatively wide range of growth adaptability and is suitable for cultivation in deep water in lakes.
3. Large green water caltrop, produced in Wujiang, Wuxian, Yixing, and other places in Jiangsu. It is a mid-maturing type, with sowing and maturity periods the same as the small white water caltrop, and a yield of 1000-1200 jin per mu. The quality is medium, the fruit shape is large, with 20-25 fruits per jin. The skin is greenish white, the shoulders are highly raised, the shoulder horns extend horizontally and are thick and large, and the waist horns are also thick. They curve slightly downward. The fruit skin is thick, and the ratio of fruit weight to flesh weight is about 2:1.
4. Water red water caltrop, produced in Suzhou, Jiangsu, Hangzhou, Zhejiang, and the Jiaxing area. It is an early-maturing type, sown at Qingming, beginning to harvest tender caltrops at Liqiu, and harvesting old caltrops at Chushu and Shuangjiang, generally with a yield of 800-1000 jin per mu. The caltrop flesh has a high water content and slightly less starch, is sweet, and is suitable for raw eating. The leaf stalks, leaf veins, and fruit skin are all water red. The fruit shape is relatively large, with 25-35 fruits per jin. The shoulder horns are slender and extend horizontally, the waist horns are medium-long and extend slightly downward at an angle, and the ratio of fruit weight to flesh weight is about 1.5:1. It is not tolerant of deep water and not resistant to wind and waves.
5. Shaobo water caltrop, produced in the Lixiahe area of Jiangsu. It is an early and mid-maturing type, harvested from Chushu to Hanlu, with medium yield, 500-1000 jin per mu, and 40-50 fruits per jin. The skin is greenish white, the shoulder horns are relatively large, the waist horns are sharp, and the skin is relatively thin. The ratio of fruit weight to flesh weight is about 1.5:1.
6. Sand horn water caltrop, produced in Wujiang, Wuxian, and other places in Jiangsu. It is a mid-maturing type, sown at Qingming and Guyu, and harvested at Liqiu and Chushu. The yield is 400-600 jin per mu. The fruit shape is small, the shoulder horns are slender, sharp, and extend horizontally, the waist horns extend obliquely toward the side of the fruit, and the skin is greenish white and thick. The caltrop flesh is hard and rich in starch, suitable for cooked eating. The roots and stems are tough, the leaves are small and densely grown, and it is resistant to wind and waves and tolerant of deep water and poor soil.
The water caltrop symbolizes “sharp edges and distinct corners” and “showing one’s talent to the fullest”, and its appearance is also quite distinctive. When eating it, you must be careful, otherwise you may get scratched.