The name primula refers to a large genus of flowering plants known by the common names primrose, cowslip and oxlip. Many of the nearly 500 species of primula are cultivated as ornamental plants for their attractive foliage and showy flowers, which occur in shades of red, yellow, purple and white. Gardeners in USDA zones 1 through 9 have the best luck growing primulas and many choose to propagate new primula plants at home. Primulas propagate readily in a variety of ways, but the simplest and most successful way of creating new primula plants is through seed propagation.
Harvest seeds from a vigorous primula plant in late summer. Pinch away the dry seed heads and gather them in a plastic bag. Crush the seed heads through the plastic bag to open them. Shake the bag to release the seeds then discard the broken seed heads.
Fill a 3-inch-deep seedling tray with potting soil. Choose potting soil with vermiculite or perlite to increase moisture retention. Moisten the soil throughout its entire depth by spritzing it with water from a spray bottle. Allow the soil to dry for five minutes before sowing the seeds.
Spread a thin layer of primula seeds over the surface of the soil. Aim for having one or two seeds per square inch, but it does not have to be exact since the seedlings can be thinned once they germinate. Lightly press the seeds into the surface of the potting soil using the flat of your palm.
Sprinkle a thin layer of horticultural sand over the top of the seeds to hold them in place and help keep the air above the tray humid. Mist the surface with water from a spray bottle until small quantities of water begin to pool on the sand.
Place the seedling tray in a greenhouse or near a southeast-facing window with bright light, good air circulation and temperatures above 18.3 degrees Celsius.
Water the seeds every other day, or when a toothpick inserted into the soil indicates the soil has dried to a depth of 1-inch. Water the seeds with a spray bottle to keep the seeds and sand from being disturbed.
Check for germination after 30 days. Thin the seedlings once they reach 1-inch in height and are starting to develop a set of true leaves. Remove any spindly or deformed seedlings and leave the stronger, healthier ones.
Transplant the primula seedlings to 4-inch plastic pots filled with moist potting soil once they develop strong anchor roots. Look for the anchor roots around the base of the stem just below the surface of the soil.
Move the transplanted primulas outdoors to a bright place with temperatures above 21.1 degrees Celsius. Keep the pots away from intense sunlight initially, but slowly acclimate them to stronger light until they can stand four hours of direct sunlight per day.
Plant the primulas in a moist, well draining bed in mid-spring. Water them to a depth of 3 inches every five days for the first month to help them establish a healthy root system.