7-14 Days to maturity. Raphanus sativus. Purple Plum Radish Microgreen Seeds. This variety of radish microgreens is known for its distinctive purple and sometimes pinkish stems with bright green leaves. Radish seeds germinate quickly and easily without the need for soaking, which makes them an excellent choice for beginners. Growing purple plum radish microgreens is an accessible and rewarding venture. ~3,500 seeds/oz.