Keeping your worms warm in Winter

It’s easy to keep worms warm in your worm farms, whatever design you have. Worms like to be little warm – they breed faster, eat more and grow fatter when they’re warm.

A few tips about keeping your worms warm

Worms and bacteria generate heat as they go about their lives. Capturing this heat and keeping it in the worm farm is the easiest way to keep the farm warm. A simple blanket or sack that covers the Worm farm is the easiest way to do this. You’ll want to use a fabric that is openly woven so that moisture doesn’t build up to too high a level. That can cause problems of its own. It’s tempting to use plastic to make the worm farm into a little greenhouse but, if you do, monitor the temperature several times a day when it is sunny – things may heat up too much. Also, make sure that there are a few holes in the plastic to allow extra humidity and heat to escape. You want to keep your worms warm, not roast them!

I favour a sack inside the farm as well, over the top layer of activity. Sacks are good because they absorb moisture and are porous, allowing oxygen and worms to pass through. They also break down slowly too.

Open weave fabric such as a sack can keep the worms warm.
Open weave fabric such as a sack can keep the worms warm.

A layer of straw or hay over the top layer of scraps also generates heat as it breaks down. It can also trap heat that is already in the bed. The straw breaks down over the winter due to bacterial and worm activity, so adds to your castings. Lucerne is the best to use, its high level of protein and other nutrients fatten up the worms nicely during the cold weather. If you don’t have access to straw, a layer of shredded paper works a treat. It also helps absorb excess moisture and the worms love to read the sports pages.

A layer of straw or shredded paper can act as a blanket.
A layer of straw or shredded paper can act as a blanket.

Mixing bran into the kitchen scraps is another way to generate warmth. As the bacteria in the Worm farm eat and break down the bran, they generate heat, as they do when they’re reproducing well because they’ve got good food. The Worms love the bran too. As with all things, don’t use too much as excess, damp bran can attract mould.

Add Bokashi scraps or Bokashi bran , or just spray the Bokashi liquid periodically can add to the warmth. The masses of bacteria in these materials are anaerobic and start attacking the oxygen deprived areas (there are a few of them in a worm farm, but not many). They also die in huge numbers in the presence of oxygen in a healthy, well ventilated and mixed bed. This sounds bad but is a good thing. It provides a feast for the bacteria, and insects, especially the Worms in the farm. They are more active and generate more heat.

Hot water bottles, wrapped in cloth so the Worms don’t come into contact with the hot surface, can be used in very cold areas. We haven’t experience of things getting that cold at Ligaya Garden, but the principle is sound.

Moving the farm inside protective shelter is another technique. Moving it away from cold wind and into an area of still air stops any heat generated being blown away.

Also, remember to keep your tap open over Winter. If it is closed, too much water can accumulate, leading to all sorts of problems!


If you want to learn more about composting with worms, click here to be taken to our ‘Compost Worms‘ page.