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Winter sowing report

In January and February, I said I'd try some winter sowing, and, this being May, I'm here to report back that I met with great success and am very happy with the technique! To recap:

1. The insight is to mimic nature's processes for germination, in a somewhat more protected environment than simply sowing seeds into the ground. In this way, we can get a jump on the growing season, yet with hardier plants.

2. The technique is to use plastic milk jugs as miniature greenhouses, and to have placed them out in the snow during the winter.

In this way, winter's freeze/thaw cycle will crack the hull of the seed, and initiate germination when it is "natural" to do so. (This really appeals to me, because I heat with wood. That means that if I try to grow seeds or plants inside during the winter, they're subject to wild temperature variations, hourly and daily, depending on when I fire up the stove, whether there's hard wood or softwood in it, how long I'm gone from the house. I think the temperature variation confuses the plants and makes them unhappy. So a temperature cycle with less amplitude is preferable, even at a lower baseline.)

3. The steps I took are as follows (and I should have pictures, but I can't find the USB cable for my camera, without even the excuse of cats).

  1. Have ready several milk jugs, scissors, a paper punch, a marker, garbage bag twisties, clothes pins, seeds, and soil. I used a big bag of potting soil.
  2. With the scissors, carefully (so as not to stab yourself) cut slits in the bottom of the jug. This is to let water drain out, just like a flower pot.
  3. With the scissors, start to one side of the handle, and make a horizontal cut all the way round the jug to the other side of the handle. Don't cut all the way around; you want to be able to hinge the top of the jug back, at the handle, when you're done. The cut should be about where the sides stop being vertical and slope inward toward the top.
  4. With the paper punch, punch a hole in each of two sides of the bottom of the jug, about half an inch down from the cut. Hinge the top of the jug down, and punch two holes in two sides of the top of the jug, each immediately above one of the holes you punched in the bottom, about half an inch up from the cut. (When you're done, you'll thread the garbage twisties through these holes to close the jug, so they need to align.)
  5. Hinge the top back and fill the bottom with soil.
  6. Open the seed packet, and add seeds to the soil. Put the seed packet aside.
  7. Cover the seeds with as much soil as the packet said to.
  8. Give the soil a good spritz of water. You don't need to soak it.
  9. Clip the seed packet to the jug at the cut using a clothespin, so you can tell what's in the jug.
  10. Close the jug by threading the garbage bag twisties through the paper-punched holes and twisting them tight. NOTE: Some advocate sealing the jug with gaffer tape against the wind. I don't, since I think some wind through the cut will make the plants more robust. Also, my garden has a heavy viral load, from the evil Norway maple, TMV, blight, and so on, and I want (admittedly without evidence) the plants exposed to their natural enemies from the start.
  11. Write the date on the jug using the marker.
  12. Put the jug out in the snow. (Bonus: The handles make the jugs easy to move.)
  13. Wait.
  14. After germination and growth, but a week or so before planting, undo the twisties, and start hinging the tops of the jugs back, so the seedlings can get used to more air and light, and the outside temperature.

And wait is right. The proponents of this method say that germination happens only after you've given up, and judging from my squash, they were certainly right!

So, the seeds germinate because of nature's freeze/thaw cycle, but the milk jugs create a warmer, more protected environment. The open cuts in the side (in my method) allow both air and water to enter. And excess moisture, if any, can evaporate through the open top of the jug!

Bottom line is that I had a success rate of 80%: More than three quarters of my milk jugs germinated, which I'm told is very good. Root vegetables did very well: I have beets and parsnips galore. The squash, though late, still germinated. And I have about six jugs of yellow and Brandywine tomatoes; I'm uncertain whether to go with them alone, or combine them with sets from my local hardware store.

The only issue I had was too much success with the root vegetables -- I ended up with root balls that filled the entire jug! So, I ended up using the HoS (Hunk of Seedlings) method to get them into rows; I don't know whether I'm happy with that, or not. Next year, I might try to figure out how to make the seedlings easier to separate out from the jug's soil, so I waste as few seedlings as possible.

All in all, I had very good luck with this technique, and best of all, there's very little work involved! (It doesn't take even as much as five minutes a jug, and the payback is huge. Plus, bonus points for recycling the jugs, this year, and, I would think, the next, and the next...).

So I'll definitely use the technique next year. Low cost, low effort, high yield: That's my kind of gardening!

And now, to figure out sheet mulch!

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gmoke's picture
Submitted by gmoke on

I tried three small containers for tomatoes, zux, and broccoli. None of them germinated. But then, I have been having bad luck with starting my own seedlings over the last couple of years.

Maybe next year, I'll buy new seed rather than use up my old stock.

Enjoyed the experiment though.

Submitted by lambert on

Perhaps that was the variable.

I put mine out from mid-February to mid-March.

They were in the best light available, at least 3/4 sun.

The winter was mild.

Also, I had about 20 containers, total. FWIW, my sense is that this is an operation best done in bulk.

Submitted by hipparchia on

i could send you some cats...

hmmm, maybe if i threaten to send you a whole herd of cats, you'd go out and buy a replacement cable or two.

germination happens only after you've given up

i can sympathize with this, even though i don't have any of the problems you do [cold? whuzzat?]. i still remember the garden that got wiped out something like 3 times in one year [there was a freeze, then a hailstorm, then a drought iic] but the volunteer squash and watermelons that grew up out of the compost heap were superb. that experience sure made me a fan of low cost, low effort, high yield gardening.