Posted on Sep 01, 2021 | by KK
Thinking back over my gardening this past season, I remembered some seeds I bought for spring that never quite made it out of the pack. Ok, ok, not quite means not at all—they were tucked carefully away while awaiting the grow light I also purchased, which sits still unused as well. Life happened, things got busy, and……….there you have it. I know I can’t be the only one—I’ve seen friends with boxes full of seeds and plenty of good intentions.
And then I remembered that just because I bought them for spring doesn’t mean I can’t use some now. There are many perennials and even some annuals that can be sown in the fall. Even better, some can be direct sown in the garden with a minimum of preparation. I suppose that means I won’t crack the box for that grow light open until late winter (hopefully the coming one).
Most gardeners are aware that fall is an excellent time to plant. Cooler soil temperatures allow plants to root better while there is no danger of frost. That’s what you want—good root growth established before the plant flushes anew. It is less commonly known that fall sowing of some seeds to expose them to a period of low temperatures is also benficial, or even necessary in some species. When referring to seeds this is called cold stratification.
Why do some seeds need special treatment? Nature has various ways of ensuring the survival of a species. Seeds will stay dormant, either by way of a hard seed coat or natural chemicals, until conditions are met that will encourage germination at the appropriate time for the plant. Some plants that drop their seeds late in the season need to keep those seeds intact until spring when seedlings have the best chance of success.
Dormancy in seeds is broken by a predetermined period of cold, cold & moist conditions, light, or darkness. This is the case for many common perennials, such as Echinacea, Penstemon, Phlox, and Rudbeckia, and many native perennials and wildflowers benefit from cold/moist stratification. That means it’s prime time for some of my ‘Green Twister’ Echinacea seeds to hit the dirt.
Preparation is minimal for direct sowing. Unless your soil is extremely compacted (and if it is you have worse problems and shouldn’t be worrying about seeds right now) just gently loosen the top inch of the soil to loosen, drop the seeds, cover lightly and water gently. You can use straw or sawdust to cover if you prefer.
Water daily to keep the seed moist during March and April if those showers don’t come your way. That’s really all there is to it—nature will take care of the rest. If seedlings are crowded come spring they can be transplanted once they have reached an adequate size. Tilling before seeding is not recommended, as you may simply be bringing weed seeds to light that will allow them to germinate. Mark the spot so you’ll be able to discriminate between any weeds and your new babies when new sprouts start growing.
If you’d rather not sow directly into the garden but still want to sow outside, you can sow in flats. This has the advantage of avoiding weed seeds and fungus that may attack new seedlings. Use new trays (about 3” deep) with drainage, or clean old ones with a 10% bleach solution. Fill the flats level to the top with a soilless seed planting mix, then using a piece of carboard compress the mix to within ½ to ¼ inch below the rim.
Sow the seeds and cover to the depth recommended on the seed packet. For easy transplanting in the spring, use individual peat pots, like our "Go-Grow" kits. This will prevent root disturbance which may disrupt growth of plants such as hellebores.
Water with a gentle spray or mist so as not to dislodge the seeds. Place the flats in a cold frame or cover with glass or clear plastic and store out of direct sunlight until spring. In March you can remove the covering and move to a spot in partial shade. Water lightly daily if needed to keep seeds moist. Within a few weeks, germination should begin.
If you still want to plant those seeds in the spring but want to increase their chances for germination, you can give them an artificial cold/moist stratification treatment in the refrigerator. Place seeds in a container with a tight-fitting lid, or a zip-lock bag with an equal volume of sand, peat moss, or sphagnum moss. You could also put them between layers of damp paper towel.
For the first 24 hours keep them wet enough so that they can absorb all the water they are able. After that, add more sand, etc. to absorb any excess water—too much water will cause them to rot. Store in the refrigerator for the prescribed number of weeks and check occasionally to be sure they are not drying out. You should time this so that once the cold stratification is complete they can be planted right away, either indoors to grow on for transplanting or directly outside in the spring.
If you have any of these seeds on the list below sitting in your drawer or box, give this a try. You may need to do a little additional research to find the best time to sow in your area for a particular plant. Depending on how cold your winters are, direct sowing could be accomplished from mid-summer to 8 weeks before your last frost.
For example, here in our Zone 7, late summer sowings would include biennials like foxglove and and Canterbury bells. Hollyhocks and bachelor buttons can be sown from August through November, and larkspur, nigella, and poppies prefer sowing after the first frost. I plan to experiment a bit to find what works best, and still save some seed to grow indoors in the spring (really, I swear).
For a busy gardener, it's nice to know that the window for starting flowers from seed is wider than we think--it's often hard to make use of all our well-intentioned seed purchases within the few short weeks of spring. Remember that the older the seed the less the percentage of germination, but that rarely means zero. In most cases there's no reason to throw away seeds that are a bit past their prime.
Or who knows? Maybe you'll spy some of these still hanging around your local garden center, feel inspired and buy more seeds (ok, like I did). Just promise me you won't store them away and forget............like me!
To view our full list of flowers for potential late summer/fall/winter sowing, click here.
As always, remember to check before you plant--all plants suggested here may not be appropriate for all growing areas. What's safe in one situation may be invasive in another. If you're not sure, let us know--we'd be glad to help. And if you've fall sown flowers in your area, let us know--sharing our experiences makes us all better gardeners!