How to Plant Dahlia Tubers and Bulbs
Dahlias are garden showstoppers, blooming with vibrant color all season long. While often treated as annuals in colder zones (USDA 3–7), dahlias actually grow from dahlia tubers—perennial roots that can be lifted, stored, and replanted.
Whether you’re new to planting dahlia tubers or looking for a refresher on how to plant dahlia bulbs, this guide walks you through everything from timing to depth to storage.
When to Plant Dahlia Tubers or Bulbs
Knowing when to plant dahlia tubers (or when to plant dahlia bulbs) is key to success. Dahlias are warm-season plants that thrive in soil temperatures between 60°F and 75°F.
In cool climates, plant outdoors about two weeks before the last expected frost. For a head start, begin planting dahlia bulbs indoors in pots about a month earlier under grow lights or in a greenhouse.
In warmer USDA zones 7–10, dahlias can be planted directly outdoors from April to early June. Keep in mind that blooms may slow down in temperatures above 90°F.
Pro Tip: Dahlias like the same conditions as tomatoes. If it’s tomato-planting season, it’s time for planting dahlia tubers too.
Where to Plant Dahlia Tubers or Bulbs
Choose a sunny location—dahlia tubers need 6 to 8 hours of direct sunlight daily. In hot regions, some light afternoon shade helps. Avoid windy spots that can damage tall stems.
Soil should be rich, well-draining, and slightly moist. Add aged compost to enrich both garden beds and potting containers.
Match dahlia variety size to garden placement:
- Tall dahlias (up to 5 ft): Great for back borders
- Medium dahlias (30–40 in): Ideal for flower beds
- Short dahlias (12–18 in): Perfect for containers and low borders
How Far Apart to Plant Dahlia Tubers
Dahlias look best when grouped in clusters of five. Space each dahlia bulb or tuber 12 to 36 inches apart, depending on mature plant size.
Allow 2 to 3 feet between tubers and surrounding plants to avoid overcrowding and ensure access for watering, feeding, and deadheading.
How Deep to Plant Dahlia Tubers
One of the most common questions is how deep to plant dahlia tubers. Here’s your answer:
- Tall varieties: 6–7 inches deep
- Short varieties: 2–3 inches deep
Recommended Method:
- Dig a 12-inch hole
- Backfill 6–9 inches of soil
- Place the tuber with the “eye” (like a potato sprout) facing up
- Cover with the remaining soil
Tip: For dahlias over 4 feet tall, plant shallowly at first and add soil as the sprout grows. This supports tall stems better. Install stakes at planting time to avoid damaging the tubers later.
Watering After Planting Dahlia Bulbs
Water newly planted dahlia bulbs or tubers only if the soil is dry—overwatering can cause rot. Once sprouts emerge, water enough to keep the soil evenly moist.
- In-ground dahlias: About 1 inch of water per week
- Potted dahlias: May need more frequent watering
How to Divide Dahlia Tubers for Replanting
Each season, a single tuber multiplies. To save and replant your dahlia tubers, lift and divide them after the first fall frost.
How to divide and store:
- Dig around the stem (1–1.5 ft out, 6–12 in deep)
- Lift the plant gently
- Find the “eye” near the main stem
- Use a sharp knife to cut each tuber with an eye and a bit of stem
- Let tubers dry in a shaded, warm place
- Store in containers with slightly damp sphagnum moss
- Keep in a dark, frost-free space at ~45°F
- Check monthly—discard any that rot or turn black
Tip: If preferred, wait until spring to divide—buds are easier to spot when they begin to swell.
Final Thoughts
Whether you’re learning how to plant dahlias, curious about how deep to plant dahlia tubers, or wondering when to plant dahlia bulbs, this guide has you covered.
With the right timing, soil, and care, you’ll enjoy stunning blooms season after season. Happy planting!
