Contact: Diane Relf, Extension Specialist, Environmental Horticulture
Posted April 1997
As we enter the last months of summer, the thought of doing another seed sowing of flowers is far from the minds of most gardeners. Flowers, after all, are either started from seeds indoors or bought in packs in spring, right? Not necessarily where herbaceous perennials are concerned. In fact, fall seeding can be used to great advantage by the home gardener.
Herbaceous perennials differ from annuals in their ability to withstand the winter and return each year from the same roots. In actuality, many of them are not just withstanding adverse conditions, but have evolved to require them. Perennials drop seeds at different times throughout the growing season, depending upon the species. The fate of those seeds usually follows one of two directions. With some species, the seeds may remain in the soil throughout the winter and germinate in spring. Other species produce seeds that germinate shortly after falling to the ground. The seedling grows several leaves before the onset of winter, but does not flower. Those seeds that wait until spring to germinate generally require cold, moist conditions of winter to erode the seed coat and allow development of the interior seedling. On the other hand, the perennial seeds that germinate readily after release from the pod often need the cold winter temperatures to stimulate the formation of a flower; without the cold, only leaves are produced.
Many cultivated perennials are easily and optimally started from seeds in August. However, seed propagation will not yield identical offspring; do not expect dozens of seedlings that all bloom simultaneously with the same plant shape and flower appearance. Expect instead to save money compared to purchasing plants from divisions, and enjoy witnessing plant genetics in action.
Seeds can be sown directly into a prepared bed. Clear the space of weeds, old mulch, and any overhanging foliage of neighboring plants. Sow the seeds generously to compensate for the unpredictable germination percentage sometimes found in perennials, and thin-out afterwards. Maintain frequent irrigation until seeds have germinated and seedlings become established. Work carefully around the new plants during fall maintenance. Seeds also may be started in seed packs or in a shaded cold frame and transplanted in late August and September. Protect the seedlings with a light mulch to enhance winter survival. In most cases, you can expect flowering for the following season. Here are a few species worth trying: Shasta daisy (Chrysanthemum x superbum), Purple coneflower (Echinacea purpurea), Cardinal flower (Lobelia cardinalis), Lupines (Lupinus x polyphyllus), Oriental poppy (Papaver orientalis), and Columbine (Aquilegia canadensis 'McKanas Giants').
(Originally published by Robert E. Lyons, Professor of Horticulture, in The Virginia Gardener Newsletter, Volume 7, Number 8.)
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