Yesterday, I spent a long time filling seed flats and pressing seeds into dirt – and then I took them outside and set them to germinate. The temps were hovering right around freezing, and there was light snow coming down – the perfect conditions for growing things. Or at least, for winter sowing
(Note, there was originally a link and short quote from a website about the subject, but the owner of the site apparently took offense because I attempted to drive traffic to her, so I strongly recommend you avoid her site, to avoid offending her. I will go out of my way never to mention it or any of her work again. )
The plants I was planting were stratified – that is, they require or tolerate a period of cold before germination. Some plants won’t germinate at all without a cold period, others will take as long as years. Others will germinate just as well. How do you know which plants will do well with winter sowing?
Anything that tells you in its germination requirements that it needs stratification or a period of cold. And anything that says “self sows” – these are all plants who seeds will tolerate or even require cold periods, gradually warming to grow. Plants native to temperate climates – anything that indicates this in its name, for example. This includes an awful lot of cold-hardy perennials, and a surprising number of garden annuals as well. Most temperate climate plants form seed in summer or autumn, and the plants have a much better chance of surviving in most cases if they don’t germinate right before winter – so a natural period of embryonic dormancy makes perfect sense for plants. Mimicking those conditions improves germination rates of many seeds, and it allows us to plant at earlier periods, less busy ones, than we might otherwise.
Now the conventional advice for stratification is to put the plants into the fridge – but I don’t have a conventional fridge, so that’s not a good choice for me. Moreover, even if I did have one, I grow a lot of plants, and would begrudge the space taken up by an awful lot of jars of seeds. And nature does a terrific job in my climate of providing adequately cold temperatures.
I do some of my seeds in trays and pans like shown in at the Wintersown site linked above, but I also start some of my plants in the fall, in nursery beds. These are garden beds that I’m done using for the year, that have good soil and a protected location – I plant elderberry, apple, quince, peach and pear seeds here, as well as juniper, black cap and cranberry bush viburnum. The plants will spend the season in this bed, or be dug out and potted up, before a final plant out.
Some plants that you wouldn’t think required stratification do considerably better with it – for example, parsley seeds, which take forever to germinate under traditional greenhouse/indoor conditions germinate very rapidly after a week of cold treatment. Tomatoes actually respond to cold treatment pretty well, although they produce later than early tomatoes will. In my climate, only cherries produce really well when grown this way, but it is an excellent way to get late tomatoes – say, if you don’t want to be standing over a canning kettle in August or if you are planting tomatoes for pots to be brought in for overwintering.
Most experienced gardeners know a little about stratification, but I think few of us have fully plumbed its possibilities – for improving germination, extending our garden season and also balancing the workload which goes with the garden.
It is too late for many southern gardeners to winter sow without recourse to the fridge, but for those of us in northern places aching to get some seeds in the dirt, now is the time!