Propagating Dahlias from Cuttings
The new shoots from dahlia tubers root very easily in the spring. The best time to take cuttings is early spring, around late February early March. For the best results the shoots should be young and vigorous and not yet become hollow.
To take the cuttings you will need a box or pot of compost to start the tuber into grown, a sharp knife or very sharp secateurs, a clean pot or tray filled with a mixture of free draining compost (made with two parts compost to one part sharp sand or grit) and a small dibber.
A propagator is best for rooting cuttings quickly but if you don't have a propagator you can still root the cuttings by placing a proprietary clear cover or clear plastic bag over the cuttings to maintain high humidity.
The general method for taking 'Dahlia Shoot' cuttings is as follows:
- Select a healthy tuber that has swelling buds at the neck.
- Place the tuber, upright, in a box or pot and cover with moist potting compost, ensuring that the buds are clear of the soil.
- Place it in a warm (7-10°C / 45-50°F), well lit but sheltered position, such as a windowsill or greenhouse to encourage it into growth.
- Once the buds start to show, water well and keep the temperature warm and even.
- Once the shoot(s) reach 7.5 cm (3 in) long or have two or three leaf nodes, they are ready to make cuttings.
- Using a sharp knife or secateurs sever a healthy shoot 7.5 cm (3 in) long, cleanly just below a leaf joint.
- Place the cutting on a flat surface and remove the lower leaves with a sharp knife, leaving two or three small leaves at the top.
- Dip the base of the cutting in rooting hormone.
- Make deep holes in your pot or tray of compost mix with a dibber. If you are putting the cuttings in a tray, allow plenty of room between cuttings to allow air to circulate, ideally spaced at 7 cm (3 in) intervals, so the leaves are NOT touching each other. Insert the cuttings, and firm them in.
- Stand the pots or trays in a tray of water for 30 minutes to allow the compost to draw up enough moisture but do not let the cuttings get waterlogged. Do not feed the cuttings at this stage.
- Place in a propagator or cover with a clear plastic cover or bag to retain moisture. Make sure that the cover or plastic bag does not touch the leaves.
Note: If you are covering a pot with a clear plastic bag to retain moisture, put some sticks around the edge of the pot to keep the plastic away from the leaves.
- Keep the cuttings in a warm (7-10°C / 45-50°F), light position but not in direct sunlight.
- Ensure the cuttings stay moist and remove any flower buds which form while the cuttings are rooting.
- After about 2/3 weeks, once the cuttings have rooted and started to form new shoots, acclimatise them to normal conditions by slowly increasing ventilation over a few days, until the cover is completely removed.
- Once a strong root system has developed pot the young plants up in a 7.5 cm (3 in) pots and water with a weak solution of tomato feed.
- Harden them of in a cold frame and plant outside once all danger of frost has passed, in May.
Dahlias can also be propagated by dividing the tubers.
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