Garden-type gladiolus can be flowered in the greenhouse during spring from corms planted in February, but I prefer the baby or winter-flowering types that provide color and fragrance during bleak February days, from corms planted in November.
Use a mix of garden loam, humus, and sand, in pots large enough to plant several corms 1 inch deep and 1 inch apart. Water well to settle corms into soil, then water sparingly until growth starts. Stems about 2 feet high produce three to five blossoms; colors may be white, pink, or red.
After blooming, keep foliage growing until it dies back naturally. Clean and store corms for the next season. Offsets can be potted as new corms, but they must grow for several seasons to develop into corms sufficiently large to produce flowers.
G. tristis, delightfully fragrant yellowish-white flowers; G. X,Colvillei, small, very early scarlet flowers.