Larkspur can easily be propagated by seeds - which you can also collect yourself. If you don't want to do much work, just wait until the plant has seeded itself.

Collect Larkspur Seeds
It is usually advised to cut off the faded larkspur stems in the summer to allow a second bloom to develop in the fall. Alternatively, you can just leave them there and wait until the narrow follicles are ready to be harvested. In these - usually each flower forms up to three of these seed pods - are the also narrow, winged seeds. Harvesting can take place as soon as the fruits are brown but have not yet opened.
Store self-collected seeds
So collect the fruit that has not yet burst from the plant and open it at home on your work table. At best, catch the seeds on a cloth or a piece of kitchen paper, which you can use to clean them thoroughly. Allow the seeds to air dry in a dark, cool place for a day or two, then place in an airtight container. They can stay there until next spring. However, keep in mind that seeds germinate less well the older they are.
Larkspur is a cold germ
Larkspur is not only a light germ, but also a cold germ. That means, self-collected seeds should be stratified before sowing to improve the germination rate. Although this measure is not absolutely necessary, it increases breeding success. Commercially purchased seeds, on the other hand, are usually pre-treated in such a way that stratification is not necessary.
Stratify delphinium seeds correctly
Prepare Delphinium for sowing by storing the seeds in a cool place for a few days, with temperatures between 0 and 5°C being optimal. However, you should definitely avoid frost. Stratification can take place from March outdoors or in the vegetable compartment of the refrigerator. Then soak the seeds in lukewarm water for 24 hours and then sow them.
tips and tricks
You can choose to grow the plants as early as March or sow them directly between May and September. Do not cover the seeds with soil, or cover them only very thinly. You should also use a net or similar to protect them from birds. The sowing site must be kept moist at all times.