Asparagus fern, known botanically as asparagus densiflorus, is a perennial flowering and fruiting herb that is not a fern, but actually a member of the lily family of plants. Much like ferns, it is used as an ornamental indoors and outdoors, and the fountain-like growth form is reminiscent of a fern. Hardy in USDA zones 9 through 11, flowering is followed by the production of small red berries, with each containing one or two black seeds. According to the University of Arkansas, the seed-laden berries are the best means of propagating the plants.
Harvest the asparagus fern berries from the plants when they are red, ripe and swollen. Collect more berries than you may actually want in new plants to account for any seed germination failures.
Crush the berries in a fine mesh strainer to separate the berry pulp from the small black seeds. Rinse the seeds in gently running water and swish with your fingers to clean them. Tap the washed and drained seeds out onto a plate or stack of newsprint to dry so they will be easier to separate and handle.
Fill a nursery pot or seed flat to within 1/4 inch of the lip with fresh sterile potting mix or seed starting medium. Nestle the asparagus fern seeds into the mix to bury roughly 1/4 inch down into the soil.
Cover over the seeds lightly with soil and water until the soil is drenched through and water runs out the bottom drainage holes.
Slide the pot or flat into a clean, clear plastic bag or cover with a length of clear plastic sheeting to create a greenhouse effect and control moisture loss.
Set the covered seed pots or flat in a location with bright light for roughly 14 hours each day and where ambient temperatures remain between 65 and 80 degrees F.
Keep the soil evenly moist and allow four to six weeks time for the seeds to germinate and begin to produce the small pale sprouts of new plants.
Remove the plastic covering slowly over a few days time, after the seeds have germinated and the young shoots have broken through the soil. Slow acclimation to the surrounding temperatures and lower humidity will lessen the stress on the young plants.