Last year, I collected and propagated seed from my black mondo grass. I now have about a hundred healthy starts which are green in color, with leaves thicker than those of the parent black mondo plants. Is this just their immature color, or do they not come true from seed?
Most of the resources I consulted recommend propagating Ophiopogon planiscapus ‘Nigrescens’ by division of clumps in fall or late winter, but The Plantfinder’s Guide to Ornamental Grasses by Roger Grounds (Timber Press, 1998) says the following:
“The flowers are mauve, but the berries are black, and if sown will produce about one-third black seedlings, the rest being green.”
If all of your plants came up green, I would guess they will stay that color (in other words, they must have reverted to the species, Ophiopogon planiscapus, which has wider green leaves).