Fall-Sown Flower Seed for Big Spring Blooms!
While you may not think of late summer as a flower-planting time, it is prime time to sow biennial and cool-season annual flower seed. Planting these flower types now (August) will give them a head start over spring planting and result in earlier and often larger blooms! If you’re a fan of fresh-cut flowers, this is a great opportunity to establish a cutting flower garden and produce your own, home-grown blooms for beautiful fresh arrangements.
Started now, the seed for biennial and cool-season annual flowers will sprout and become well established before the cold weather slows their growth. The plants will overwinter, growing very little during the cold months, and then take off with a surge of growth once the days lengthen and temperatures rise in early spring. This is especially effective for biennial flowers, which have a 2-year lifespan and don’t bloom until the second year. The cold period of near dormancy is called vernalization, and biennials require it to set their buds. Starting these seeds at the end of summer will minimize the length of time it takes these plants to mature and bloom. Cool-season annuals are varieties that thrive and bloom in cooler temperatures. Depending on your growing zone you may see blooms from these types opening as early as late winter from a late summer planting.
Some of our favorite varieties for late summer sowing include:
Dianthus
Sow the seed when Mother Nature is dropping them (approximately 4-6 weeks before your first frost in the fall). This timing allows the seed to sprout and the plants to set roots prior to the onset of cold weather. Direct sow sweet peas, calendula and poppy; transplant others. For the transplanted varieties, sow the seed indoors in flats. They’ll be ready to transplant into the garden when they have 2-3 sets of true leaves. For best results, the plants should be protected from harsh weather. High tunnels, cold frames or hoops with row covers will usually provide adequate protection for the young plants throughout the winter. Here in our zone 8b, Oregon winters, we have great success growing overwintered flowers in an unheated greenhouse. The structure offers shelter from wind, rain, snow, and gives the plants an earlier jump-start in spring. Occasional irrigation is necessary to keep the plants happy.
For taller flowers, pinch the plants to encourage branching & heavier blooms. When the seedlings are 3-5 inches tall, pinch them to half that height. They will produce multiple stems and more flowers. The downside is that pinching may delay flowering over unpinched plants. To get the best of both worlds—earliest and most abundant blooms—pinch about 1/3 of your plants and leave the rest.
Pro Tip: Taller flowers perform best when grown with support. We use trellis netting stretched horizontally over the flower beds. As the plants grow through the netting, it helps keep them upright, clean, and straight stemmed. The overall height of the plants will determine the ideal height for the netting. For a 30-inch-tall snapdragon, we’ll install a trellis netting support at about 12-16 inches from the ground.
Your growing zone and individual conditions will determine which types of flowers will be good candidates for overwintering. Get creative and experiment with several varieties to find out which work best for you.
Author: Kat B.
