Tendergreen mustard seeds Seeds Brassica Rapa Vegetable Seeds. 45 days. . Milder than regular mustard greens, this variety has thick, smooth leaves on upright, heat and cold tolerant plants. Tendergreen is widely used both in stir fry and in salads. Its tender leaves, as well as its flowering stems, are used raw or are cooked and have a flavor between mustard greens and cabbage. A cousin to kale and collards, mustard is a tenacious leafy green but it's not as cold-hardy. Grow in clumps about 12-18 inches apart. Use straw mulch to hold in soil moisture. Start 4-6 weeks before the first frost for a fall harvest. For a spring harvest, start seeds 4 weeks ahead of the last frost. You can harvest and allow to regrow over a period of a couple weeks as long as the weather permits. Cut leafy greens 3-4 inches from the ground and allow sufficient time to regrow. Spinach Mustard Komatsuna Greens Brassica Rapa Vegetable Seeds. 45 days. Mustard-Spinach or Komatsuna. Milder than regular mustard greens, this variety has thick, smooth leaves on upright, heat and cold tolerant plants. Tendergreen is widely used both in stir fry and in salads. Its tender leaves, as well as its flowering stems, are used raw or are cooked and have a flavor between mustard greens and cabbage.