Winter Sowing Container Options

Choosing the right container is probably the most important determinant of winter sowing success so I’ve brought together what I’ve learned from many years experience with many types of containers. At the end of this article is a list of criteria that will help you decide whether a container is worth trying.

There are two variations on the mini-greenhouse concept. First is the all-in-one, where the part that holds the soil (germination mix) is attached to the greenhouse top. Second is what I call a big top setup, where a large jug holds several smaller tubs or pots that contain the soil.

All-in-one types

Pop Bottles

These are probably the easiest containers for beginners. I like the ‘hourglass’ shaped ones because they can be cut so that the top fits over the bottom, which requires less tape and is easier to pop open if you need to add water or check for germination.

Pop bottles in a basket will keep the squirrels from knocking them over. Note the extra venting holes and the label that can be read from the top.

You can use straight-sided bottles (ones that don’t ‘nest’)– just line up the top and bottom and tape all the way around.

Left: An hourglass-shaped pop bottle showing cutting lines. The bottom part should be about 4″ tall.
Below: The bottom part that will hold the seeding mix. Note the position of the drainage holes– on the bottom of the curves.

More examples of ‘all-in-one’ containers. I would not advise using opaque tape, though. As well, additional vent holes and better labelling are needed here.

If you sow directly into the bottom of a large container (as this gardener did with the top left jug) you’ll end up with a lot of seedlings that you may not need. As well, four inches of seeding mix in a lot of large containers can get expensive.
For efficient use of seeding mix and space, consider using these large jugs to hold several smaller containers. I call this a ‘big top’ setup.

‘Big Top’ setups

A ‘big top’ is simply a large jug that holds several smaller containers. The jug is the greenhouse; the containers are the pots that hold the soil. Pots do not need lids or tops.

Translucent Jugs

Look for large jugs that once held vinegar, kitty litter, cooking oil, detergent, etc. They need to be translucent or transparent, not opaque.

I almost always use these to hold smaller containers, for several reasons.

Because the sides of these large jugs are not very rigid and when moved or handled, they bend. Cracks will open up in the germination mix and seeds sometimes get buried in the crevasses.

But the main reason I don’t like planting directly into big jugs is the sheer number of seedlings they can hold. I usually don’t want a bazillion of a single species–and I don’t advise growing more than one species per container, for reasons I won’t go into here. Yes, I could sow more thinly and get fewer plants, but that’s a waste of expensive germination mix and also not an efficient use of the limited space on my back deck. I prefer to sow thickly in smaller containers such as deep mushroom tubs, 3.5″ pots, or 500ml yogurt tubs. Each holds a single species and they nestle securely into the big ‘greenhouse’ jugs.

The photo at left shows a really large jug holding four smaller tubs. The two on top are deep mushroom tubs.

Below is a smaller jug that nicely holds two 2″x3″ cell-inserts.

Left: three jugs before being cut. These look opaque but they’re actually translucent.
Below: Jugs and bottles outside.

Here’s a setup using a greenhouse tray with a high dome. Inside are either cell inserts or smaller containers.

The amount of air space above the soil level is important. This ‘head space’ prevents overheating, allows for air circulation, and permits seedlings to get quite tall before they hit the ‘roof’.

photo: copyright Pam McDonald

Getting creative

A google image search using ‘winter sow’ or ‘wintersowing’ will result in hundreds of container ideas that gardeners have tried. When deciding if something will work or not, keep the following in mind:

  • Is there enough head space?
  • Is the top transparent or translucent? Blue or green tints may work (I have not tried them) but I suggest that beginners stick to non-tinted tops.
  • If the part that holds the germination mix is opaque, can it be filled to the very top? If you only partially fill a pot, the part above soil level will cast shadows on the soil surface.
  • How big is the soil-holding container? You will be sowing only one species per tub, so unless you’re planting the entire back 40, a small one is usually just fine. Remember, though, that the smaller the pot, the faster it dries out. So if you’re using really small pots (such as cell inserts) be sure to regularly check the soil moisture levels in the spring. Be wary of using peat pots, which tend to keep seedlings either too soggy or too dry.
  • Can you cut or melt holes in the greenhouse material? This rules out glass and thick plexiglass.
  • Can the greenhouse top withstand strong winds and the weight of big dumps of snow? I’ve experimented with setups using clear plastic bags, but I never found a reliable way to prevent them from collapsing onto the soil surface.

This gardener is using a variety of containers. The opaque tops probably won’t work but the other options are fine.

Styrofoam cups, plastic ‘solo’ cups or any type of pot with opaque sides are good for situations where the light is directly overhead at all times, such as in an indoor setup with grow lights. Outdoors, though, the sun (in winter and spring in the northern hemisphere) is low in the sky. Opaque pots will cast a shadow over the soil surface, causing seeds near the edges to germinate later than the rest. To avoid this, fill opaque containers to the very top and tamp well to minimize settling.

Here’s my haul from neighbourhood blue bins on recycling day. The blue-tinted jug and the yogurt tub did not make the cut.

All containers can be saved, cleaned, and re-used next year.

Whatever containers you choose, keep records of what worked well and if you try something new, do a ‘backup’ jug, just in case.

Have fun! This is the wonderful end result!