Worm Composting In Vermont Winters

“Just read your current newsletter (3 Apr) Regarding species of worms – what will survive with least attention in Vermont? I would love to be able to use the “red wigglers” in my compost bin – I have plenty of horse manure to add. But I have not been able to get them to overwinter. Thank for your answer.” ~ Jane.

Hi Jane,

As mentioned in my “best worms” article (the one you are referring to), in terms of overall versatility, the European Nightcrawler (Eisenia hortensis) and/or the Red Worm (Eisenia fetida) – also known as ‘Red Wiggler’ – will almost always be your best choices.

If you provide the basic requirements for these worms – food, moisture, and a protective environment – they should do just fine in Vermont. They are very easy to please, but they certainly can’t be neglected altogether.

During the summer months you should protect their system from overheating and drying out (of course assuming we’re talking about an outdoor bin), and in the winter extra steps will be needed to protect your worms from the freezing temperatures as well.

The fact that you have plenty of horse manure on hand is a major bonus – this is an excellent food material for composting worms (once it has been precomposted or aged) and will really help when it comes time to create your winter worm home.

As mentioned in previous newsletters, I have an insulated outdoor worm bin that worked quite well for me this past winter – even with total neglect for much of February and March (i.e. no food waste added), the contents never froze solid and the worms survived quite easily.

While I think this type of system could be successfully used in many cold regions, I suspect that something more substantial, or a different approach altogether, would be needed in areas where winter is much more severe – perhaps Vermont falls in this category.

Based on what you wrote, I suspect that you simply left your worms in your regular backyard composter and hoped for the best. Unfortunately these bins offer next to no protection from freezing temperatures, and are not big enough to hold the amount of materials needed to stimulate ‘hot composting’.

I’ve successfully overwintered worms in the bottom of these systems before – but I always dig a hole in the ground beneath the composter and I suspect the worms bury themselves down below where it likely never freezes solid.

If I lived in Vermont (or some other northerly locale) and had lots of horse manure I would almost certainly make a very large system to contain my outdoor worms for the winter. If you can get a hold of straw bales you will have yourself some fantastic insulated building blocks and some great material to mix with your horse manure as well (this might not be needed if your horses use straw bedding).

Simply stack the bales to create the walls of your worm bed. The bigger the volume the better – since more material will be able to generate more warmth, and for longer period of time. Bare minimum it should hold at least 2-3 cubic yards.

Once your walls are up, simply pile in a mixture of manure and straw (fall leaves would also work well). This material can then be covered with another thick layer of straw to help keep the heat in. You will want to let this mix heat up and cook for a period of time (perhaps a couple weeks) before attempting to add the worms. With a system like this you could probably continue composting all winter long, and can certainly keep your worms alive.

You could also take a much simpler approach if you just want to keep the worms alive (i.e. you don’t have any interest in outdoor winter composting). Just dig a trench in the ground and add the contents of your backyard composter (assuming it has composting worms in it).

Over top, layer manure with any or all of the following: fall leaves, straw, shredded cardboard, peat moss. Be sure to pile these materials nice and high, since aside from providing a source of food, they will also offer protection from the cold. If you get a lot of snow in your area be sure to heap a nice thick layer of it over top of your worm bed once it arrives.

My good friend Jeff (‘The Friendly Worm Guy) recently shared his success with using this method to protect his outdoor worm beds. He lives in Northern Ontario, where winter conditions can be very severe (colder than Vermont, that’s for sure). Apparently Jeff’s beds were absolutely teeming with worms by the time spring arrived!

Anyway, just some ideas things to think about, Jane!

Hope this helps.

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