Starting Cool-Season Annuals for Early Spring Blossoms

On By durhammastergardenersIn Uncategorized

By Marcia Kirinus, EMGV

Fall is rapidly approaching, and for me, it marks the start of spring planting. The shorter days and cooler nights inspire seed starting of cool-season hardy annuals. I have a particular fondness for early spring annual flowers because they are the first to bloom after a dreary winter. They fill empty spaces with vibrant blossoms and serve as a crucial food source for early-season pollinators. I’m referring to flowers like Centaurea, poppies, Digitalis, snapdragons, larkspur, and Calendula. While the list is much longer, these are just a few of my personal favorites.

All photos by Marcia Kirinus

From left to right, top to bottom: Snapdragon (Antirrhinum majus), Foxglove (Digitalis purpurea) Bachelor’s button (Centaurea cyanus), Feverfew (Tanacetum parthenium), Annual Monarda (Monarda hybrida), larkspur (Consolida ajacis), Strawflower (Bracteantha bracteata), Sweet William (Dianthus barbatus).

Cool-season annuals thrive in cool to cold conditions and bloom early in the spring through summer. Planting them now instead of in the spring has substantial benefits. When planted in the fall, they get a significant head start. Throughout the winter, they develop deep root systems, resulting in larger and more robust plants come spring. Their stems are longer, and they produce more blossoms. They also become more resistant to diseases and insects. However, my favorite reason to plant now is that after you sow seed or plant transplants, there is little else the gardener must do but occasionally water. In contrast, when you plant in the spring, your plants will remain small and require more attention.

To determine if a plant is a good candidate for fall planting, there are a few things you need to know.

  • Your USDA winter hardiness zone.
  • Your average last frost date.
  • The hardiness survival zone of the plant you want to grow.

This knowledge enables you to sow all kinds of plants in the fall, not just cool-season annuals. Herbaceous perennials, ornamental grasses, and shrubs can be treated the same way.

In Durham, NC, we reside in USDA winter hardiness zone 7b (although we’re occasionally a bit cooler in the northern part of the county). This means I can plant anything that is winter-hardy up to zone 7. Anything that survives the winters of zones 7, 6, 5, 4, 3, 2, or 1 can be either transplanted or seeded directly. To determine when to plant, you need to know your first average frost date. Currently in Durham it falls between November 3rd and 9th.

Once you have your winter-hardy seed, your USDA winter hardinesss zone, and your first average frost date, sit down with your calendar and plan accordingly. If a seed packet says to start seed 4-6 weeks before maturity, count back from November 15. Ideally, this puts you at sowing seeds between October 15-25. You can start them indoors or sow them directly in the garden. Often, the seed packet will tell you if one method is preferred. If you are putting transplants in the ground, you have a little more wiggle room, and they can go into the garden later than 4-6 weeks. Last year, I experimented with putting transplants in the ground in late November, into January. I then covered them with a light fabric row cover, and most did just fine. I’m not sure how they would have survived without the row cover. The covers are mostly to protect the young plants from the harsh wind, not the temperature.

Some plants do better when started indoors and set out as transplants, while others thrive best when seeds are sown directly. Directly sow seeds of: nigella, poppies, bupleurum, agrostemma, larkspur, centaurea. Flowers that do better as transplants include snapdragons, digitalis, and calendula.

From left to right: Calendula (Calendula officinalis), Soapwort (Sapornaria ocymoides), Chinese forget-me-not (Cynoglossum amiable).

When directly sowing seeds, read the back of your seed packet or get seed germinating info online from the distributor. Many of the cool season annuals require light to germinate – meaning you do not cover the seed with soil. Toss them and walk away. Many want cool nights when the air temp is 65-70 for two weeks, and the soil is still warm. Last year in Durham, that time was around Halloween. That was when I scattered poppies, bells of Ireland, orlaya, cynoglossum.

Plants from scattered seeds of Orlaya grandiflora, California poppy (Eschscholzia californica), Soapwort (Sapornaria ocymoides).

Lastly, keep in mind that not every seed will germinate, especially with direct sowing. I typically start with three times more seeds than I need for direct sowing and one and a half times more for indoor starting. This way, you can select the healthiest transplants and compost the rest. Don’t expect every seed to germinate or thrive.

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