Temperature extremes have their challenges.

Within in two days of each other I have had questions about worm bin composting in the heat and in the cold.  I thought I would try to address each of these issues at the same time.  

• Please note:  specific temperatures are guidelines only and are established through my own experience.  Each situation is unique and has many other variables that will come into play such as exposure to wind, sun, excess moisture, size of bin, ambient temperature, etc.

Good sized, healthy redwiggler, not mature yet - no clitellum.

Red worms, specifically Eisenia fetida, are very hardy and can withstand temperature extremes better than many other species.  Even so, as the temperatures ease out of the optimum range the worm will become stressed and will cease to eat and become lethargic.   

This is a mature worm, as you can clearly see the clitellum.

Surprisingly enough,  Eisenia fetida likes their home environment to be in the same temperature range as the rest of us, between 68 and 72 degrees.  While this is the ideal range, the worm will happily continue working at a low range of 50 degrees all the way up to the low 80’s.  Once the temperature extends beyond these extremes the worm will cease eating.  Ideal mating temperature ranges are probably a bit narrower than that, but if the herd feels threatened they will often produce more cocoons, as the cocoon can survive extreme hardships. 

Specific question dealing with heat issue is this: 

I am in North Texas and we will likely have extreme temperatures in the summer….at its worst we can go several days with highs in the upper 90s and lows in the high 80s–plus we will have some stretches of 100+ degrees.  Are there ways to keep the worms cool in these conditions? I could put them in the garage I guess…but I would rather have them outside.

 

Also, can you just use a meat thermometer to measure the temp of the bedding?

Now, it is important to remember that ambient temperature (outside air temperature) is not as important as the temperature in the bin.  While the outside air temperature does ultimately effect the temperature in the bin, the bedding acts as insulation.  The bigger the bin, the better the insulative qualities.  Also, the length of time that the outside air temperature is at the extreme will come into play as well.  The best thing to do in these extremes is to have a compost thermometer to accurately gauge the temperature in the bedding where the worms are. 

That being said, the temperature of the bedding is where it is important to keep tabs on the temperature.  It is imperative you understand that you are working with a composting system here.  Ideally the worms are doing the composting for you, but as you add various components to the system (bedding, food stock, water, air) you are providing the perfect conditions for the material to start composting without the aid of the worms and thus the temperature will be on the rise.  

In these situations, when the outside ambient temperature is on the rise as well, it will be very important for you to keep a very close eye on the conditions inside the bin.  

HOT AND DRY WILL KILL YOUR WORMS!

THE ONLY THING WORSE WOULD BE A TOXIC CONDITION !

Here are some things that will help keep your bins cooler in extreme heat: 

1. Watch what you are putting in the bin.  Don’t mix it up too much when the temperatures outside are on the rise.  Add food stock in small amounts.  If you have a lot of food waste to process, build an additional conventional compost pile where you can put your food waste to pre-compost.
2. Additional moisture – evaporation is a natural cooling mechanism.  Think of how your own body cools itself when it is overheated, you sweat!  However, care must be taken that you do not create a toxic condition where there is too much moisture and not enough air.  The moisture needs to be applied lightly and often.  I have found a nice insulative layer of shredded newspaper helps. 
3. If the bin is smaller and mobile make sure it is in plenty of shade and out of any drying wind.  Also see to it that the excess moisture has somewhere to go.  If the bin is too big to move and is in an undesireable location then protection must be provided.
4. Finally, if you have a stretch of hot temperatures and the temperature in the bin is rising to an alarming level you may have to help the evaporation process along by adding some air movement along the surface of the bin.  I have been known to set up a small fan at the end of each bin to blow across the surface of the bin.  More moisture will have to be added to compensate for the moisture loss.  But don’t overcompensate and drench the bedding.  Keep a close eye on the moisture level in the lower portions of the bedding. 

The heat issue is a delicate dance and can be a bit more complicated than the other end of the spectrum. 

Here is the question about extreme cold: 

You commented that E. foetida impressed or surprised you in their
ability to take the cold. I was wondering how cold have they been and
survived it? I keep mine in the kitchen nearly year-round without much
trouble-only an occasional fruitfly explosion when there’s lots of
fruit in the summer–it would be nice to know their tolerances should
there be some sort of outbreak like the fruitflies in cold weather. It
would be really useful to know how cold they can take it, so I know
when it’s safe to have them outdoors on the porch and when they must
come in. 

I live in zone6-7 and we do sometimes get down to zero, but not every
year and not for long when we do. So…could you elaborate about the
cold? Or if it’s already covered somewhere in  your blog, perhaps you
have a link? Haven’t got round to reading it yet, but I mean to. I’ve
had my worms about a year now. 

What this person is referring to is a video I made about my bins one spring after spending the winter without heat.  The differentiation here is that my bins are big compared to most indoor bins.  My bins are 4′ x 8′ heated fiberglas bins.  Again the mass of bedding aids in insulating the worms from extreme temperatures. 

I also work my bins in such a way as to have active composting producing heat in the bins as we go into winter.  However, even considering these specifics, I was still amazed that my worms survived frozen bedding.  The bedding was not frozen solid, I could still insert a compost fork into the bedding, but the bedding was definitely in the freezing zone. 

But, I would still advise against putting an indoor bin outside regardless of the situation for a couple of reasons. 

1. An indoor bin does not have the insulative mass of a larger bin.
2. The bin has been acclimated to indoor temperatures and would not adjust to suddenly being thrust into any extreme, be it cold or hot.
3. Once you have an outbreak of fruitflies, putting the bin outside will only serve to leave the fruitflies flying aimlessly around your kitchen or where ever you have had your bin.

Instead I would avoid any fruitfly problems by handling the food waste in such a way as to discourage them.  Besides, I have never had a fruitfly problem in the winter. 

1. Wash all fruits and vegetables well before you use them.  This is something that is encouraged anyway, but especially wash the fruits that harbor fruitflies – bananas, cantaloupe, etc
2. Freeze all food waste before adding it to the worm bin, this will effectively kill the eggs that have hitched a ride home with you.
3. Bury all food waste beneath a thick layer of moistened, shredded newspaper.  This acts like a blanket over your composting food waste and is easily pulled back to check on the bin and to add fresh food waste.  It creates a barrier to any flying pests that would try to use your food waste to lay eggs in.

Avoiding a problem during temperature extremes is always better than thrusting your bin out into extreme temperatures to fix the problem later.  

That’s it for now.  Please let me know if I have created further questions regarding handling your bins in temperature extremes.  

Remember that your worms will thrive under specific conditions and your job is to try and keep your bins functioning under those conditions. 

Happy worming! 

Christy
Handle your organic waste the way Nature intended.
http://www.vermiculturenorthwest.com/