DAHLIAS
Growing dahlias from seeds is a rewarding, fun and easy project
1. When to Start Indoors
Start your seeds indoors about 4 to 6 weeks before your area’s last expected spring frost date. In Zone 7b, this is typically around late March to early April.
Dahlias need a long growing season to bloom well and produce roots/tubers before autumn, and starting them indoors gives them a head start.
2. Sowing the Seeds
Fill seed-starting trays or small pots with a light, well-draining seed-starting mix. Moisten the soil so it is damp but not soggy.
Press the seeds lightly into the soil surface or cover them with about 1/4 inch of soil, as they need a little bit of darkness or light contact to germinate, but cover helps anchor them. Space them a couple of inches apart if in a flat, or put 1–2 seeds per small pot.
Place the trays in a warm spot (around 70°F to 75°F). Cover the seeds with a plastic dome to retain humidity until sprouts appear The seeds will sprout in 2 weeks
As soon as the seedlings emerge, remove any humidity domes and place them under grow lights or in a very bright space south-facing window.
Dahlias need 14 to 16 hours of light daily to prevent them from becoming leggy and weak.
4. Hardening Off and Transplanting
When the temperature consistently stay above 50°F (usually late April to mid-May in Zone 7b), begin hardening off your seedlings. Gradually and gently move them to outdoor over 7 to 10 days by placing them outside in a sheltered, shady spot for a few hours at first, slowly increasing their exposure to direct sun and wind.
Plant them out in a sunny location that receives at least 6 to 8 hours of direct sunlight a day. Space them about 12 to 18 inches apart in rich, well-draining garden soil or large containers.
5. Ongoing Care and Summer Maintenance
Water deeply at the base of the plants rather than overhead to keep foliage dry and prevent powdery mildew. Seed-grown dahlias will have their first buds and opening flowers by mid-summer and will grow flowers the rest of summer
When the plants are about 12 inches tall and have 3 or 4 sets of true leaves, pinch out the central growing tip. This encourages branching, resulting in a bushier plant with significantly more flower stems.
Feed them with a balanced, low-nitrogen fertilizer (or compost) every few weeks to encourage abundant blooms rather than just massive green foliage.
By autumn, your seed-grown dahlias will have produced underground tubers. If you want to save them for next year, you can dig up and store the tubers after the first light frost blackens the foliage!
Dahlias planted from seeds will form underground tubers by the end of the growing season.
Even though they start from tiny seeds, as the plant grows and matures through the summer, it builds a root system that swells into a cluster of small tubers underground.
