Dahlia imperialis 'Double White' (Tree Dahlia)

This double-white form has lots of crisp white petals, resembling a big, white pom-pom. The blooms lack the orange center of the original pink form, because of the fluffy petals and petaloid stamens. The plant tends to grow a bit shorter than the original form, topping out at about 5-6m tall. The attractive stems grow to 10cm thick and are hollow like bamboo. The stems were actually used by the ancient Aztecs as pipes to carry drinking water. This variety is sometimes referred to as Dahlia imperialis 'California Angel'. The single white variety is very rarely cultivated.

Cuttings available from April to September, only in limited quantity. The 1.5L plants are halfway through rooting. If you order these before end of October, please keep them in their pots for a few weeks before repotting or planting in the ground.

Dahlia imperialis (tree dahlia) is quite easy to propagate from stem cuttings. In New Zealand, spring to early summer is a good time, particularly once new shoots are actively growing.

INSTRUCTIONS FOR GROWING FROM CUTTINGS

Method 1: Detailed method

Optional: dip the base in rooting hormone (IBA). It isn't essential, but can improve consistency.

• Use a very free-draining medium (50% perlite + 50% coco coir or 70% perlite + 30% quality propagation mix)
• Insert 1–2 nodes below the surface
• Firm the medium gently around the stem
• Water thoroughly once
• Keep at approximately 18–25°C
• Bright light but no strong direct midday sun
• High humidity helps, but maintain ventilation to prevent fungal problems
• Keep the medium slightly moist, never saturated

Method 2: Easy method

• Insert the lower end of the cutting into any potting mix to about 1 or 2 nodes
• Keep moist and well watered

Method 3: Root in water

• Place the cuttings in a container of water with the lower 1-2 nodes below the water
• Keep the container in a sheltered area

It takes usually 2–4 weeks, although cooler conditions can make it longer. Gently tugging the cutting after about 3 weeks can indicate whether roots have formed—don't pull hard.

Once you see new growth and the cutting resists a gentle pull, transplant it into a small pot.