AMES, Iowa – As fall approaches, it’s time to start thinking about germinating seeds for the upcoming growing season. Starting them outdoors and then transferring inside can lead to good results. How can this be accomplished?
ISU Extension and Outreach horticulturists can help answer your questions about germinating seeds.
How do I germinate butterfly weed seeds?
Harvest the seed pods of butterfly weed, Asclepias tuberosa, when the pods begin to split. Seeds can be sown directly outdoors in late fall or started indoors.
When sowing seeds outdoors, work up the soil in a protected location in early to mid-November. Scatter the seeds over the prepared seedbed and then cover the seeds with approximately one-fourth inch of soil. The cold, moist conditions over winter improve seed germination. Seedlings should emerge in spring. Carefully transplant the seedlings to their permanent locations when the seedlings are three to four inches tall.
To start seeds indoors, fill a flat with a commercial germination medium (such as Jiffy Mix). Moisten the medium. Scatter the seeds over the surface of the germination medium and lightly press the seeds into the material. Cover the seeds with an additional one-fourth inch of the germination mix. Carefully moisten the additional material. Slide the flat into a plastic bag and place the bagged flat in the refrigerator. Leave the flat in the refrigerator for four to six weeks. After that, remove the flat from the refrigerator and place it in an area with a temperature of 70 to 75 degrees Fahrenheit. Seeds should begin to germinate in three to four weeks.
If no seedlings appear after four weeks, place the flat back in the refrigerator for another four to six weeks and repeat the process.
Take the flat out of the plastic bag as soon as seedlings appear and place the flat under fluorescent lights in a 60 to 65 degree Fahrenheit location. Transplant the seedlings into individual pots when the seedlings are one to two inches tall. Continue to grow the seedlings indoors under fluorescent lights for several more weeks. Prior to planting outdoors, place the seedlings outdoors in a shady, protected location and then gradually expose the seedlings to longer periods of direct sun. Plant the seedlings in their permanent locations after they have hardened outdoors for seven to 10 days.
How do I germinate Jack-in-the-pulpit seeds?
Jack-in-the-pulpit (Arisaema triphyllum) seeds can be sown directly outdoors or started indoors. Harvest the cluster of berries as soon as they turn red in late summer. Each berry usually contains four to six seeds. Remove the seeds by gently squeezing them from the berries. Seeds can be planted immediately outdoors. Plant seeds one-half inch deep in a moist, shaded location.
Jack-in-the-pulpit seeds can also be started indoors. Before sowing the seeds indoors, the seeds must be stratified (exposed to cool, moist conditions) for 60 to 75 days. Jack-in-the-pulpit seeds can be stratified by placing them in moist sphagnum peat moss or fine sand and then storing them in the refrigerator for two to two and a half months. Suitable storage containers include small plastic bags and food storage containers. After the seeds have been stratified, remove the seeds from the sphagnum peat moss or sand. Plant seeds one-half inch deep in a commercial potting mix. In spring, plant the seedlings outdoors.
How do I germinate purple coneflower seeds?
Purple coneflower, Echinacea purpurea, seeds can be sown directly outdoors or started indoors. Exposing the seeds to cool, moist conditions (stratification) usually improves germination.
Outdoors, plant seeds in fall. Cover the seeds with one-eighth to one-fourth of soil. Seedlings should emerge in spring. Seedlings can be transplanted to different locations later in the growing season.
Indoors, fill a flat with 1.5 to 2 inches of a commercial potting mix. Sow seeds on the surface of the potting mix and cover with an additional one-eighth to one-fourth inch of material. Moisten the potting mix, slide the flat into a plastic bag, and place the flat in the refrigerator for two months.
After that, remove the flat from the refrigerator and place it in an area with a temperature of 70 to 75 degrees Fahrenheit. The seeds should germinate in 10 to 14 days. Take the flat out of the plastic bag as soon as germination occurs. Transplant the seedlings into small pots three to four weeks after germination. Grow the seedlings indoors several more weeks before planting outdoors.