Timing your indoor seed starts is one of the most important aspects of cut flower gardening. Start too early and seedlings become leggy and pot-bound; too late and you lose weeks of potential harvest. This schedule is based on your last frost date—adjust all timing accordingly.
Lisianthus needs the earliest start of any common cut flower. Sow now.
Snapdragons, stock, eucalyptus, delphinium. These are slow growers that need time.
Rudbeckia, dusty miller, ageratum, scabiosa.
Strawflowers, celosia, marigolds (if transplanting).
Cosmos (if transplanting), amaranth.
Zinnias, sunflowers, cosmos, nigella, marigolds. These do best sown directly in warm soil.
Use a seed-starting heat mat for tropical species like celosia. Provide strong light (a grow light 2–4 inches above seedlings) to prevent legginess. See hardening off before transplanting anything outdoors.