Taking dahlia cuttings is one of the easiest ways to increase the number of plants in your cut flower patch. Propagating these plants by cuttings is also a great way to get the most for your money. The process is relatively simple and only requires some very basic equipment. 
First, we’ll need to select a stem to use for our cutting. I like to use cuttings that are nice and large, so that I can divide them into multiple cuttings. Taking cuttings from your existing dahlia plants will not harm the plants. Since dahlia plants need to be pinched back anyway (to encourage more growth), the pinchings can be used to make more plants. Remember, you’re not allowed to take cuttings from patented varieties. 
To make the cutting, I use a blade to cut the stem. Avoid using scissors, if possible, as they can damage the stem of the plant. Make the cut just above the leaf joint of the plant. Ideally, our new growth will begin from the leaf joints of the cutting. 
After making the cut, there are a couple options. You can definitely dip the cuttings into a rooting hormone to help the cutting take root. I personally never use rooting hormone and always have really great success. 
Now that the cuttings have been placed into the tray of moist potting soil, it will be important that conditions remain consistent. Since I’m taking cuttings in the spring, I’m going to leave the tray outdoors in the shade or in a very sheltered location. For the first week, I’ll make sure to mist them with water on a daily basis. Within 2-3 weeks, roots should have started to form on the plants.
If the weather is still cold where you live, this process can be done with the use of a milk jug or 2 litre bottle. The jug, when left in the sun, will act as a miniature green house propagator. This process of taking plant cuttings always relies heavily on trial and error and simply finding out what works best for your garden.
