This spring, I took a little tour of a community garden with a friend (just a visit, as I’ve been on a waiting list for years to get my own space, what a torment!). A woman was pulling lettuces out of the ground, looking discouraged. When she saw us, she offered us each several heads of lettuce – she had far too many. Despite the early date, she had a full bed of beautiful, plump heads of lettuce. “How did you manage to get so much lettuce so early in the season?”, I asked her between bites of the delicious leaves. “Simple,” she replied, “I sowed in the fall and that’s it!”
Pre-seeding consists in sowing plants, often fruit and vegetables, before winter so that they can start growing when spring comes.
The principle is simple: in autumn, before the ground is frozen but temperatures are low enough to prevent the seeds from germinating, plant your seeds in the garden as you would in spring or summer. This is a good time to add compost, if you wish.
Obviously, this technique works best in colder climates, where the soil freezes and stays frozen for most of the winter. Canada is the perfect place to do it, as we regularly have sub-zero temperatures and snow cover most of the winter.
Timing Is Everything
Successful pre-seeding can be tricky. First, you need to know the germination temperature of the plant you want to grow. Let’s take lettuce as an example, which generally germinates when the soil temperature is between 4 and 27°C (39-80?). So, you need to plant when the mercury stays below 4°C (39?). There’s a bit of latitude, of course. Your lettuce won’t sprout all at once when it’s warm enough; it needs a few days of good weather. The main challenge of pre-seeding is knowing when to plant, since you have to do it before the ground freezes.
The most difficult problem to overcome is the successive freezes and thaws we often experience at the start of winter. If a thaw lasts long enough, your seeds could germinate and the seedlings freeze when the cold returns. So there’s no guarantee of success. However, it is possible to resow in the event of crop loss.
What to Plant in Pre-Seeding?
We often think of vegetables in this context, but you could just as easily plant seeds for annuals, perennials and even lawns. Cold-hardy plants are excellent choices for pre-seeding, especially if they can tolerate a light frost. Think of all those vegetable plants that are planted before the last frosts of spring, such as peas, lettuce, radishes, cabbage or spinach.
There are also all those annuals and perennials that resow themselves, such as cosmos and sunflowers, which could be planted in autumn. It’s the natural cycle of these plants to produce seeds during the summer, so that they emerge in the spring. Many of them even need this cold period to germinate. When we start these plants indoors, we have to do a cold stratification for the seeds to hatch. Wouldn’t it be simpler to sow them outdoors in autumn? Bear in mind, however, that the survival rate of outdoor seedlings, exposed to weather, insects and animals, will be lower than in the controlled conditions found indoors. If you have few or expensive seeds, it may be better to sow them indoors to better control growing conditions.
In the case of vegetable plants with a long life cycle, it will probably be best to start them indoors too. Although tomatoes can be sown in autumn, they are unlikely to produce fruit in this situation.
Pre-Seeding a Lawn
When temperatures remain below 10°C (50?), most grasses found in lawn seed mixtures will stop germinating, or at least germination will slow down. You can seed from this point until the ground is frozen.
Read Larry Hodgson’s article on the subject:
A Few Plants to Pre-Seed
Here’s a non-exhaustive list of plants that can be pre-seeded in autumn, along with their germination temperature (soil temperature).
Vegetables and Fruits
Swiss chard (Beta vulgaris flavescens) 10-29 °C (50-85?)
Beet (Beta vulgaris conditiva) 24-29 °C (75-84?)
Broccoli (Brassica oleracea var. italica) 21-27 °C (69-80?)
Carrot (Daucus carota) 24 °C (75?)
Celery and celeriac (Apium graveolens) 18-24 °C (64-75?)
Ground cherry (Physalis pruinosa et autres) 20-29 °C (68-84?)
Cabbage (Brassica oleracea capitata et autres) 7-30 °C (45-86?)
Kale (Brassica oleracea acephala) 7-35 °C (45-95?)
Squash (Cucurbita pepo et autres) 21-32 °C (70-90?)
Spinach (Spinacia oleracea) -1-24 °C (30-75?)
Lettuce (Lactuca sativa) 4-27 °C (39-80?)
Turnip (Brassica rapa rapifera) 10-35 °C (50-95?)
Onion and shallot (Allium) 18-29 °C (64-84?)
Parsnips (Pastinaca sativa) 16-18 °C (60-64?)
Leek (Allium porrum) 18-29 °C (64-84?)
Peas (Pisum sativum var. macrocarpon et saccharatum) 4-24 °C (39-75?)
Radish (Raphanus sativus) 7-42 °C (44-107?)
Rutabaga (Brassica napus) 16-29 °C (60-84?)
Basil (Ocimum basilicum) 15-21 °C (59-70?)
Chervil (Anthriscus cerefolium) 10-13 °C (50-55?)
Chives (Allium schoenoprasum) 15-21 °C (59-70?)
Coriander (Coriandrum sativum) 13-18 °C (55-64?)
Dill (Anethum graveolens) 15-24 °C (59-75?)
Fennel (Foeniculum vulgare) 18 °C (64?)
Garlic chives (Allium tuberosum) 20 °C (68?)
Lemon balm (Melissa officinalis) 20 °C (68?)
Oregano (Origanum vulgare) 21 °C (70?)
Parsley (Petroselinum crispum) 15-21 °C (59-70?)
Thyme (Thymus vulgaris) 15-21 °C
Amaranthus (Amaranthus caudatus) 21-24?
Annual Chrysanthemum (Chrysanthemum carinatum and C. coronarium) 15-21? (59-70?)
Bachelor’s button (Centaurea cyanus) 15-21? (59-70?)
Balsamine (Impatiens balsamina) 21-24? (70-75?)
Black-eyed Susan (Rudbeckia hirta) 18-24? (64-75?)
Blue Tansy (Phacelia tanacetifolia) 13-18? (55-64?)
California Popply (Eschscholzia californica) 13-15? (55-59?)
Chinese Forget-me-Not (Cynoglossum amabile) 18-24? (64-75?)
Clarkia (Clarkia unguiculata) 13-21? (55-70?)
Cleome (Cleome hasslerana) 21-24? (70-75?)
Coreopsis (Coreopsis tinctoria) 13-20? (55-68?)
Corncockle (Agrostemma githago) 13-18? (55-64?)
Cosmidium (Cosmidium burridgeanum) 15-20? (59-68?)
Cosmos (Cosmos bipinnatus and C. sulphureus) 24-27? (75-80?)
Flowering Tobacco (Nicotiana sylvestris) 21-24? (70-75?)
Godetia (Clarkia amoena) 13-21? (55-70?)
Larkspur (Consolida ambigua, C. regalis, formerly Delphinium) 10-13? (50-55?)
Lavatera (Lavatera trimestris) 21? (70?)
Love-in-a-Mist (Nigella spp.) 18-21? (64-70?)
Morning Glory (Ipomoea tricolor and I. nil) 21-27? (70-80?)
Opium Poppy (Papaver somniferum) 13-20? (50-68?)
Painted Sage (Salvia viridis) 18-21? (64-70?)
Pansy (Viola x wittrockiana) 15-20? (59-68?)
Policeman’s Helmet (Impatiens glandulifera) 20-22? (68-72?)
Portulaca (Portulaca grandiflora) 18-21? (64-70?)
Pot Marigold (Calendula officinalis) 21? (70?)
Scarlet Flax (Linum grandiflorum) 18? (64?)
Shirley Poppy (Papaver rhoeas) 13? (55?)
Sunflower (Helianthus annuus) 20-30? (68-82?)
Sweet Alyssum (Lobularia maritima) 25-28? (77-82?)
Sweet Scabious (Scabiosa atropurpurea) 18-21? (64-70?)
Sweetpea (Lathyrus odoratus) 13-18? (55-64?)
Tall Verbena (Verbena bonariensis) 15-20? (59-68?)