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Forcing dahlia: more bang for your buck by starting tubers early

Dahlia forced tuber

To give your dahlias a head start and especially to multiply them through cuttings before the final planting, forcing is a practical and effective method. Simply pot up your tubers in a heated area starting from February-March.

Also read:

A surprising flower

Splitting dahlia to get moreGardeners generally all know about dahlia. Yet, seeing their subtle hues and surprising shapes for the first time always amazes.

Did you know dahlias originally grew for tuber consumption? They reached Europe only in the late 18th century. Today, this Asteraceae family member, native to Mexico, has thousands of cultivars mainly for ornamentation!

Its head might resemble a simple or double flower, like that of a daisy. It might have the grace of an anemone or water lily flower. But forms like cactus dahlias turn into stunning spiked balls. Dahlia sizes vary in stem height and flower size. This flexibility makes them perfect for flower beds, planters, or as cut flowers.

Growing dahlias yourself lets you enjoy them more and even share them with friends. Often sold individually or in threes as large tubers, they can get pricey if you’re planning to create a display across your entire garden. Plant them in sun-warmed soil around April or May (refer to our planting days calendar for more details).

2- Forcing steps

In February and March,

  1. Forcing young dahliaSmall crates or large polystyrene containers that stand about 8 inches high (20 cm) are perfect. Make sure water can easily drain out through the drainage holes. Fill them with sand or a lightweight soil mix, and be sure to moisten it well.
  2. Take the tubers out from their packaging and give them a little squeeze between your fingers. It’s important to make sure they’re firm enough. If any tuber feels dehydrated or rotten, set them aside. Got a tuber that’s much larger than the rest? Divide it into smaller sections. Just make sure each section has a shoot or eye bud.
  3. Splitting a dahlia root clumpWith a sharp and clean knife, get to work splitting the tuber bunches. Sprinkle any cuts with crushed charcoal. You can multiply a single dahlia into 4 or 5 depending on tuber size. But if you’re planning to prepare cuttings later on to get even more, it’ll help to keep the tubers rather on the large side.
  4. Bury the tubers about 6 inches apart (15 cm) and stand them up in the sand-filled crates with the shoot just peeking out of the soil. Keep everything between 60 and 65°F (between 15 and 18°C) in a well-lit spot, like a not-too-warm lean-in or sunroom.

3- Continue with cuttings

Once shoots start appearing, you can start taking cuttings nearly immediately. To avoid weakening your plant, stick to taking weaker shoots, those on the side. They wouldn’t produce flowers on the main plant anyways as they are, so turning them into self-standing plants will give them a chance to bloom.

But patience! Wait until they’re about 3 inches long (7-8 cm) before cutting.

  1. Dahlia cuttingsGently brush away soil to reveal tubers and use a grafting knife to pull or cut the shoot, taking a chunk of tuber with it.
  2. Bury it immediately about 1 inch (2-3 cm) deep, either directly in ground or in a pot, after removing base leaves.
  3. Water your cuttings moderately and keep them in a location with at least 59°F (15°C). When they show signs of growth, pinch them above the third leaf. This will bulk up the base.

These cuttings will grow as strong as their parent plant and bloom together with them. Once there’s zero chance of frost, typically around April or May, transplant your rooted cuttings in the garden:

  • Spacing of 20 inches (50 cm) for larger varieties and 8 inches (20 cm) for dwarf ones is ideal.
  • Pick a sunny, open spot away from walls.
  • Loosen soil deeply using a digging fork, enriching it with well-decomposed manure, compost, or organic fertilizer. Ensure proper drainage to steer clear of rot.

→ More Dahlia insights:

Images: adobestock: Екатерина Сулина; Nature & Garden contributor: Eva Deuffic; iStock: Andrea Obzerova; Pixabay: Michael Kauer

Written by Eva Deuffic | Eva is passionate about gardens and gardening, and her talented words –and sharp camera– take us away on beautiful adventures.
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