Microgreens Seeds- Oakleaf Lettuce This is a green loose-leaf variety famous for its re-growth. Harvest the outer leaves and they will be replaced with tender new leaves in a week of two. A real producer that works equally well in the garden or a container. 90% Germination. These greens should be harvested when the plants are 10 to 14 days old. They can be grown in moist paper towels (bleach-free) or in a soil mix.