Protecting Composting Worms In Winter

Worm Composting...

“This is our first winter since we started. My question is what should I do to protect my worms? Our beds are 3’x8’x16″ and I use mostly mule manure to feed. I have heard everything from hay to insulation. We live outside Augusta, Ga. and our winters are really unpredictable. Some nights might go to freezing and sometimes not. We say around here if you don’t like the weather just wait a day and it will change.” ~ Donnie

Hi Donnie,

The fact that you live in Georgia certainly lessens the need for serious winterizing of your beds, but it still never hurts to err on the side of caution.

You didn’t mention what sort of beds you have, but assuming they simply sit on the ground, there are a variety of steps you can take to keep them fairly warm.

One of the keys to keeping a worm bin active in the winter is…

1) generating a substantial amount of microbial heat, and

2) insulating the system well enough to keep as much of that heat in as you can.

Stimulating microbial heating requires that you have a steady supply of rich organic material with a C:N in the range of 20:1 to 40:1, and enough volume to sustain this heating – essentially you will be relying on a mild version of ‘hot composting’ to keep your system warm.

If you mix your mule manure with straw and heap it on during colder weather that should provide both warmth AND insulation. The only potential issue in your case is the size of your system – the width and depth are a little smaller than I would feel comfortable with during one of our winters, that’s for sure (I’m in Canada though – so no comparison).

In all honesty, if the lowest temperature you need to contend with is the freezing mark, you definitely won’t need to worry about your worms dying. This is assuming we are talking about Red Worms (Eisenia fetida) – tropical species, such as Blue Worms and African Nightcrawlers will start to die once temps start dipping below 50 F. Red Worms on the other hand are very hardy and can withstand really cold temperatures.

Really, as long as they don’t freeze solid they will be ok. Just to give you some idea of their cold tolerance – I have been finding them alive and kicking in material that is basically frozen (I’m in the process of moving worms and bedding from an unprotected system to a much larger winter bed).

One thing I should mention – there is definitely a big difference between keeping your worms alive, and maintaining a highly functional system during the winter. As I’ve pointed out, it’s not really that hard to protect your worms from dying – but if you expect your system to continue performing as well as it does during warming months you will definitely need to work a little harder. 🙂

Aside from straw, fall leaves can provide excellent insulation and long-term food source. I rely heavily on them myself, and it never hurts that the worms seems to love them.

You mentioned hay – this is another great material if you can get a hold of it. It has a lower C:N ratio than straw – so it can help to generate heat and provide good nutrition for the worms – but it can also provide good insulation value. Alfalfa straw is another material with similar properties (and advantages).

You also mentioned ‘insulation’ – I’m assume you are referring to household insulation? I actually used some old insulation (that was sitting in my dad’s basement) last year to insulate my big outdoor worm bin. I simply built an addition outer wall around my bin, lined it with cardboard, then stuff the insulation down in the space between the two walls. It worked quite well!

Anyway, hopefully I’ve helped to get you pointed in the right direction. Good luck!

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