15 to 20 minutes. Tiegun yam is a specialty of Jiaozuo City, Henan Province. It has extremely high edible value. It can be eaten after steaming it for 15 to 20 minutes. It contains cellulose, amino acids, trace elements, etc., and has extremely high nutritional value. high. Tiegun yam is a perennial vine with long cylindrical tubers that can reach more than 1 meter in length. The stems are right-handed, hairless, and have single leaves. They are alternate at the lower part of the stem and opposite above the middle. The leaves are ovate-triangular to broadly ovate. Or halberd-shaped, apex acuminate, base deeply heart-shaped, broadly heart-shaped or nearly truncate, edge often 3-lobed to 3-lobed, dioecious, male inflorescences are spikes, 2 to 8 borne in leaf axils. The female inflorescence is a spike, with 1 to 3 borne in the leaf axil. The capsule is not reflexed, and is triangular and oblate or triangular in shape. The flowering period is from June to September, and the fruiting period is from July to November.