60 days. The Rainbow Mixture Swiss Chard seed mix is a blend of colored. The crops can grow in zones 6 and up, and the leaves can be harvested after fifty days. The Rainbow Mixture Swiss Chard leaves have a bitter taste, similar to spinach. Our own blend of colored chards including red, yellow, orange, white, and vivid pink stems that merge into dark green savoyed leaves. Slow to bolt and quite lovely in bunches.