Extension Educator, Horticulture
Sesame Street's cookie monster says "cookies! give me cookies!" gardeners say "plants, give me plants!". The easiest and quickest way to get more perennial flowers is to divide existing plants in spring. Gardeners are very generous with their plants. In addition most perennials perform better if they are divided periodically. Plus divisions have the advantage of maintaining the parent's characteristics. If you need many plants and have some patience, perennials can be started from seed.
Seeds may be required to obtain some perennials that are not readily available as plants. There is also something quite satisfying in starting plants from seed. It's also cheaper than psychological counseling for cabin fever.
Some perennials are easy by seed. Columbine, purple coneflower and black-eyed Susan will naturally self-sow. As the flowers brown and ripen, the seeds fall to the soil to germinate the next season. If self-sowing is desired, be sure to let old flowers remain on plant until seeds ripen and refrain from heavy mulching in self-sown areas. Keep in mind seeds from hybrids will generally not produce plants exactly like the parent.
Some perennial flower seeds require very specific conditions before they will germinate. Seeds come programmed to germinate at the appropriate time when the seeds have the best chance of survival. Do some homework to discover specifics for the plants of interest. Patience is a requirement when starting perennials from seed. Most do not flower the first year from seed and some may take several years.
The most common form of seed dormancy is seed impermeability. In other words the seed coat does not allow water to be absorbed. Water is necessary to get the germination gears moving.
Nature provides this treatment in some plants with the help of birds. Birds eat the seeds then deposit them in a nice mound of fertilizer. You could follow birds around and take your chances. A better method is to soak seeds overnight or nick seed coat with a sharp knife or a quick swipe or two with sandpaper. There is no need to take the complete seed coat off. Plants in the bean, tomato or morning glory family often have hard seed coats.
Plants that are native to cold climates may also need a period of cool weather followed by warm weather. Yes, some things actually need cold.
The easiest way to supply a cool period is to plant seeds in fall so they experience a natural winter. Unfortunately these seeds are subject to the perils of outdoor living. Planting seeds in pots and placing in a cold frame or protected area outdoors will also work.
A more controlled method is cool stratification. Most of our seeds will need a cool moist period of 34-41 degrees F (1-5 degrees C). Place seeds in plastic bag with moist sand or sphagnum moss. Place in refrigerator for at least 4 weeks. The timing again will depend on the plant specifics. Seeds do not need to freeze and freezing may actually slow down the process. Refrigerator is best for most. This method also seems to get most seeds on the same page so they germinate at the same time.
After the recommended pre conditioning, seeds can be sown indoors similarly to producing annual flowers and vegetable transplants. Some perennials are notorious for slow germination. If the seeds don't germinate the first year, place the container outside in summer and keep it watered. Seeds may germinate the next year or the next. Did I mention patience as a prerequisite?
Some good reading about plant propagation: The Complete Book of Plant Propagation by Jim Arbury et al, Making More Plants by Ken Druse, From Seed to Bloom by Eileen Powell and the textbook Plant Propagation: Principles and Practices by Hartman, Kester and Davies.