Mid-winter sowing in Canada

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Mid February is usually the coldest time of the year here in Ontario… And in 2015 it was the coldest on record. A good time to play inside in the plantroom and do my winter sowing. I get a lot of seed from specialty clubs, most of which is hardy geraniums, with a few alpines and other perennials. A lot of these need ‘cold treatment’, which they get by being sown now and placed in the cold garage to experience the natural fluctuating cold of winter.

I must bring in any bags of soil, bins of mulch, and stacks of pots days before I need them, so they can thaw out. Night time lows have been reaching -30C, so they are frozen solid and even the pots are stuck together!

I have had good success for years by using two different mixes in my winter-sown pots. The top level is a good quality soil-less potting mix which provides a fairly sterile medium to sow the seeds in. The middle is a good quality garden mix such as triple-mix, because the seedlings can wind up staying in the pots well into the summer, if I don’t get all the required new beds prepared in time. The wood chips are added first, simply because I have them and it saves purchasing mixes to fill the pots.

Sometimes there can be a mild spell above freezing, and I do not want the seeds germinating too early… So I top off the pots with a little snow to keep them cool and also to maintain a little moisture.

I love the society seed exchanges, as they provide seeds of plants that I would never find at local garden centres. The club volunteers that organize and run them do an amazing job. Also thanks to those that donate seed! We must however, remember that there is no real control on what a hobbyist grower sends in… Once in a while you get something that is not what it is supposed to be. A few plant species are notorious for this. I keep getting Erodium trifolium when I order Erodium pelargoniflorum and my orders of Geranium yoshinoi always turn out to be Geranium thunbergi… But I keep trying!

Not all seed is sown and allowed to freeze… Those species from warmer climates that do not come close to a real Canadian winter, such as those from South Africa and the Canary Islands, they are sown a little later and left in the warmer side of the garage where the mature plants of this type over-winter.

You must be careful not to sow too early in the season, or the seedlings will get too large before they can be eased outdoors. I keep moving the date later, and now try to wait until March Break before doing the non-cold treatment sowings.

These February sown (indoors) seedlings got far too large and lanky before they could move outdoors. The real challenge is how long the germination will take… This can run from a few days to a few weeks, all from the same seed. If you could predict the germination time better it would be easier, but it will vary.

It was amazing how early this rock cress germinated… It was still quite cold and it had no light in the unheated garage!

If it is warm enough, seedlings need to get eased into real sunlight as soon as possible. Be careful not to give them too much the first times!

The tricky part of choosing a sow date is that all the seed does not germinate at the same time… Some species sprout sooner than others, and even within a batch of seed the times can vary… So you usually wind up with seedlings at various stages… Just the nature of the game!

By the end of April the indoor seedlings are ready to get outside on good days.

This is why I like to have soil with nutrients in the pot… They don’t always get planted in-ground as soon as they should.

• 17 Feb, 2015
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