Dahlia Tubers vs. Seeds: Which Should You Plant?

Dahlias can be grown two ways, and the choice shapes your entire season — what you get, when you get it, and how much it costs.

The case for tubers

A tuber is a clone. Plant a ‘Café au Lait’ tuber and you get ‘Café au Lait’ flowers — the exact colour, form, and size you saw in the photograph.

• Flowers the same season, usually 8–10 weeks after planting.
• Predictable — essential if you are planting a colour scheme or growing for market.
• Established plants handle slugs and dry spells far better than seedlings.
• Higher cost, typically several dollars per tuber, and named varieties sell out.

The case for seeds

Dahlia seed is cheap, germinates readily, and produces flowering plants in a single season.

• Volume — one packet can yield 50 or more plants for the price of a single tuber.
• Variation — seed-grown dahlias are not identical to the parent. This is a drawback for a formal border and a delight for a cutting garden.
• No storage — seed keeps for years; tubers must be lifted and stored frost-free.
• Slower start — sow indoors 6–8 weeks before the last frost.

Which should you choose?

Choose tubers if you want a specific variety, are planting a designed border, grow for cut flowers to sell, or want the least fuss in year one.

Choose seed if you want a large cutting garden on a budget, enjoy the surprise of new colours, or garden in a short season where losing a few seedlings does not matter.

Why not both?

Many growers do exactly that: named tubers for the varieties they rely on, and seed for filler and experimentation. Seed-grown plants also make excellent cut flowers, and any seedling that performs outstandingly can be saved as a tuber for next year.

Planting tubers: the essentials

1. Wait until soil is above 12°C — dahlias rot in cold ground.
2. Plant 10–15 cm deep, 40–60 cm apart, eye pointing up.
3. Do not water until shoots appear; the tuber stores enough moisture.
4. Pinch out the growing tip at 30 cm for a bushier plant with more flowers.

Starting seed: the essentials

1. Sow indoors 6–8 weeks before last frost, at 20°C.
2. Cover lightly — dahlias need light to germinate.
3. Pot on when two true leaves appear.
4. Harden off over a week before planting out.

Overwintering

Tubers must be lifted after the first frost blackens the foliage. Cut stems to 10 cm, dry for a week, then store in a box of dry compost at 5–10°C. Seed-grown plants can be treated the same way — dig the tuber clump and store it.

Browse dahlia tubers for named varieties ready to plant.