Three questions many ask us in Extension this month include what are some good fall flowers other than garden mums, how to overwinter tender dahlias and gladiolus, and how to collect seed for next year from this year's flowers.
Garden mums are the standard fall flower for color. In the colder parts of our region, they should be called fall mums rather than hardy mums, as most won't survive consistently from year to year. Flowers that are perennial, and will survive and provide fall color, include Helen's flower (Helenium) and fall asters. You may find Helen's flower called Sneezeweed, but it is the ragweed not this flower that causes fall allergies. There are many types of asters, from new low hybrids suitable for containers, to the tall New England asters (three to four feet tall).
There are some great new cultivars (cultivated varieties) of goldenrod you might consider as well. These do not even resemble the common wild ones, and as with the Helen's flower do not cause allergies. For annual flowers for fall, consider some of the many ornamental kales and cabbages with white to purple foliage. You may also find potted pansies and other annuals that will tolerate a light frost.
Dr. Lois Berg Stack, of the University of Maine Cooperative Extension, recommends cutting dahlia stems back to one foot high just before a hard frost. Remove root clumps from the ground, digging wide and deep to avoid damage. Gently tap off the soil, then allow the clumps to dry for a few hours before packing into sand or dry vermiculite in a paper bag. Store cool (35 to 40F) and dry over winter.
Check roots monthly, and add water only if they are shriveling badly. In spring, cut apart the tuberous roots when they sprout, making sure each piece has a new sprout on it. Pot them or plant directly in the garden.
For gladiolus in the fall, allow them to grow at least six weeks after flowering. They can receive some heavy frosts. Then lift carefully with a garden fork, shake off soil, and allow the corms (rounded bases similar to bulbs) to dry for a few days. Store cool and dry as with dahlias, only in paper bags, trays, or boxes.
Most herbs and a number of annual and perennial flowering plants are good choices for seed collecting in the fall, according to Margaret Hagen of the University of New Hampshire Cooperative Extension. Any plant that is a true botanical species-- one that is not produced by commercial hybridization and extensive selection-- can be grown again from seed from the parent plant. Keep in mind that many annual flowers are hybrids, so wont come true (offspring wont resemble parents) from seed. Neither will perennial cultivars (cultivated varieties) closely resemble their parents in many cases.
During the fall you can collect seed from dill, thyme, basil, bachelor buttons, lavender, hollyhocks (these often cross too), cosmos, some snapdragons, many wildflowers, and others. If seeds are borne in a flower head, cut off the seed stalks just before the seeds are dry and start to scatter. Dry the stalk, then rub or shake the seeds off into a bag for storage. If the seeds are in a pod-like structure, allow the pods to turn brown before harvesting. Dry the pods in a warm, dry site and then shell as you would peas. Label and store seeds in a cool, dry place such as airtight jars in a refrigerator.
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