To propagate dahlias, you will need sharp scissors, potting soil in a container, and something to poke holes into the soil with like a dibber, a pencil, or a spoon handle. You can also use rooting powder to encourage root growth.
On a healthy dahlia plant, find a long side shoot with at least 3 leaf nodes.
Cut just under the last node you want to include. (The roots will grow from the bottom and the last node)
Keep your cuttings fresh in a container of water while you collect more.
Trim off the leaves on the last node, and remove any flower buds. You want the cutting to focus on growing roots instead of supporting flowers.
Dip the cutting, including the last node, into the rooting powder and tap off the excess. Be careful not to touch or inhale the rooting powder. Use gloves if necessary.
Note: it is not necessary to use rooting powder.
Make a deep hole into your potting soil with your poking device, and insert the dahlia stem. Use your poking device to push soil against the cutting so that it is buried.
Water your cuttings generously and put them in a warm location with indirect sunlight. They should be ready to transplant in 2-4 weeks.
Dahlia Propagation - Week Two
Dahlia Propagation - Week Three