“ALPHABET” (not an anagram, a logic puzzle)

1 – Melinis nerviglumis
2 – Encelia farinosa
3 – Kalmia latifolia
4 – Ophiopogon planiscapus
5 – Clematis dioscoreifolia
6 – Iris japonica
7 – Quercus rubra
8 – Geranium himalayense
9 – Astrantia bavarica

Ab, Cd*, Ef, Gh, Ij, Kl, Mn, Op, Qr

(* I went with the plant label, but learned after I made up the puzzle that Clematis dioscoreifolia is a synonym for Clematis terniflora)