Dahlia Seed Guide
Starting dahlias from seed requires care and attention for best results, but is achievable and so worth the effort! Each dahlia seedling is totally unique in the world, will flower profusely in it’s first summer, and will typically produce a tuber clump that can be harvested as usual. All named dahlia varieties originated this way, and Burfoot Flowers dahlia seed comes from the very same stock we use for our dahlia breeding program!
We would love to follow along on your dahlia seedling journey and see what you grow! Tag us on Instagram, or shoot us an email!
The recommendations below are simplified with the goal of balancing success with familiarity and ease for home gardeners. If you would like industry standard recommendations for the highest likelihood of success, I highly recommend the book ‘Dahlia Breeding for the Farmer-Florist and the Home Gardener’ by Kristine Albrecht, of Santa Cruz Dahlias!
WHEN: Start dahlia seeds indoors under artificial light and heat, 6 weeks before last frost date.
PREP: Fill 4” pots with high quality potting mix that has been lightly hydrated. It should feel damp but not wet. Place pots in seed starting tray and label with variety and seed starting date.
SOW: Germination will occur over 7-14 days, with a germination rate of 50-75%. Poke two holes in each pot with your finger, about 1” apart, 1/4” deep. Place one seeds per hole and cover lightly with soil.
GROW: Cover seed starting tray with a clear plastic dome lid. Place trays under bright grow-lights, keeping the seedlings 3-6” from light. Place trays on seed starting heat mats, aiming for a soil temperature of 70 degrees and no higher. Monitor and water as needed, allowing top layer of soil to dry between watering. Once the first set of true leaves emerge, remove humidity dome and turn heat mat down to 65 degrees. If needed, transplant seedlings to one per pot.
PLANT: It is best to harden off your dahlia seedlings, to prevent transplant shock. Seven to ten days before transplanting, start introducing your seedlings to indirect outdoor sun and mild (50-60 degrees) outdoor temperatures. Move them back inside at night. Gradually acclimatize them to outdoor life. After all risk of frost has passed, plant out seedlings into your garden. Dahlias need full sun, fertile, well drained soil, and consistent water. Space your dahlia seedlings 18-24” apart. Place a tall stake next to (or tomato cage over) your dahlia seedling at planting. Install drip irrigation or soaker hoses. Protect from slugs.
PINCH: When plants are 12-16” tall, pinch them by cutting just above a set of leaves. Remove 3-4” off the top of the plant, leaving a minimum of 4 leaf sets. This will force the plant to branch from the base and produce more flowers on longer stems.
TEND: Tie dahlia seedlings to the stake as they grow to keep them upright. Irrigate dahlias deeply, 2-3 times a week during the dry season. Always monitor for drought stress and water as needed. Dahlias appreciate a mid-season fertilization with a mild, balanced fertilizer of your choice such as compost tea, or worm castings. Avoid heavy nitrogen fertilizers during blooming.
HARVEST: For best vase life, harvest when the petals are unfurled, but still firm at the back, and the yellow center of the flower is flat and without loose pollen. If you want to keep your dahlia blooming all summer, keep harvesting consistently. If you loved your seedling and want to grow it again next summer you can dig up the tubers and store them like any dahlia, or take a gamble and leave the plant in the ground, doing your best to protect from frost and moisture.