Mustard Seeds - Tsa Tsai Round Stem. Heirloom. Brassica juncea var. linearfolia. 120 days. Cool season annual. Tsa Tsai is a popular and unique mustard variety from Southwest China and called Szechuan or Sichuan vegetable. It is also known as swollen stem mustard or pressed stem mustard because the stem enlarges into thick tuber-like bumps just below the petioles. ~18,400 seeds / oz.