Taking dahlia cuttings

Bright, showy dahlias are a highlight of the late summer garden. You can increase your stock by taking basal cuttings from tubers in spring. Each tuber will give you around five new plants for free that will flower in summer.

Now we are in March this is a good time to pot up dahlia tubers (from storage or buy new ones), to bring them into growth, so you can have new shoots sprouting after a few weeks. Once healthy shoots have grown, leave some on the original tuber so that the plant can grow away strongly. Cuttings may wilt initially, but pot them up quickly and water well, and they’ll soon recover.

Rooting will occur after a few weeks, after which you can expect more substantial plants which will need potting on. Harden them off before planting in late spring after the danger of frosts has passed and give young shoots protection from insects and particularly slugs, which love to eat them.

You Will Need

· Dahlia tubers

· A sharp knife

· Multi-purpose, peat-free compost

· Seed trays or pots

· Hormone rooting powder.

· Horticultural grit

1. When stems reach 7 to 8 cm long, they should make good cuttings. Take a good look at the stems coming from your tuber and choose which stems to cut. You may need to push the compost aside so you can see where the stems emerge from the tuber. Stems that can be severed from the parent with a small amount of tuber intact are the first to try. This is because the growth hormones needed for good root development are concentrated in the tuber.

2. Take a sharp knife. This can be a gardener’s knife but a kitchen knife will also do. Ideally the knife should be clean and some growers advocate sterilisation through a flame. Hold the chosen stem and push the knife into the tuber and under the stem to cut it away.

3. If some of the light brown woody tuber comes with the stem, you have a perfect specimen. If not, don’t worry as the stem can still be used but you will need to cut the stem under a leaf node as shown in the first picture below. A leaf node is simple to spot as there is a swelling on the stem from which the leaves emerge. It should root anyway as there is also a concentration of growth hormones in the leaf node. If you want to you could dip the cut stem into some hormone rotting power or gel but this is not essential.

4. Carefully tear or cut away any lower leaves on the stem and cut the top leaves in half to reduce the amount of surface area through which moisture can be loss.

5. Fill a pot with compost. Place a pencil into the compost at the edge of the pot to make a hole and put the stem in, gently firming the soil around it. Three cuttings can usually be fitted around the edge of a 9cm pot.

6. Water the cuttings. They usually root without covering but if you have a propagator (plastic tray with or without bottom heat and with a clear plastic lid) you could use this. You could also try putting clear a plastic bag over the pot, held in place with a rubber band. Both methods reduce the moisture loss from the cutting but have the potential for the cutting to rot if the atmosphere is overly damp – so do not overwater.

7. Cuttings will take 2-4 weeks to develop roots. Resist the temptation to pull the stem to see if it has taken. You will know when it has worked as the stem will begin to grow new leaves. Alternatively, if you have some, use the see-through pots used by orchid growers, or even the plastic cups from children’s parties (with drainage holes punctured in the bottom) as you can see the roots growing without disturbance.