Vermicomposting in Arid Regions

Here is a question from Tom:

My big , honkin’ super HUGE , most important and almost life changing question deals with moisture (or LACK thereof). Here in Arizona we have about 6% humidity in the summer . I tried a bin and got it as wet as common sense would allow only to find it drying out at the speed of light by midday . I’m wondering if I can’t set up a soaker hose in one section and keep it REALLY wet while addressing the other areas as the need arises during the day . The reason that it is sooo important is that I’ve read where folks feed and ignore them for days . With the status quo I cannot even leave for a few days for fear of returning to a WHOLE lot of dried crooked sticks interspersed throughout a big box of bedding that crackles to the touch . As much as I don’t want to kill little helpless wiggling souls is the thought of losing good money . Help me PLEASE!!!

Hi Tom!
You’re in luck – I love “big, honkin’ super HUGE, most important and almost life changing” questions!

Joking aside – you’ve certainly hit upon a really important topic here. It’s not something I’ve really talked all that much about. One reason is that I live in a fairly typical temperate region – i.e. moderate temps with decent levels of humidity during spring/summer/fall (so I’m not really all that familiar with hot, arid environments). I also tend to be a wee bit reserved on this front simply because I don’t want people to end up overdoing it – something that’s very easy to do when using a run-of-the-mill plastic, enclosed worm bin (likely the most common vermicomposting system in use).

You didn’t mention what type of system you are using, but I’m going to assume that it’s NOT a plastic, enclosed bin. While there’s no doubt that this type of bin is great for holding in moisture, this can definitely be a curse in a hot/sunny outdoor location. These systems tend to readily soak up and hold in heat, and have next to no evaporative cooling capacity.

My general recommendations for a hot dry climate would be:

1) Use some sort of wooden bin – preferably partially sunken into the ground (with a decent pit underneath), sitting in a shaded location if at all possible.

2) Maintain a thick layer of bedding materials over the exposed surface of the composting zone at all times. Not sure what materials might be available in a hot dry region (don’t imagine fall leaves, and hay/straw would be all that common – haha), but see what sort of carbon-rich waste materials you can track down (dry grass clippings? etc).

3) Add plenty of slow-release water-rich waste materials. If you freeze fruit/veggie waste ahead of time you’ll have the added benefit of helping to lower temps in the bin (helpful during hot spells).

4) Employ other hydration methods – your soaker-hose idea is great as a back up strategy (if you still can’t manage to maintain moist conditions – or if you are going to be away from home for a few days etc), but even perforated (with really tiny holes) plastic jugs filled with water would likely help a lot, while conserving your water a bit.

5) Make sure you have lots of excellent water-holding materials in the bin – especially in the central zone. If you soak coir bricks and bury them in various locations, for example, every time you add water they should help to wick a lot of it up and then slowly release to the surrounding environment. I suspect that you could even get some good mileage out of old cotton towels, cloths, shirts etc (the added benefit being that it would take a long time for these to disintegrate).

Anyway – just my 2 cents, Tom! Perhaps others will chime in with ideas as well.
Hope that helps a bit!

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    • Jim Burdine
    • February 10, 2011

    I live here in the Mojave desert in the Las Vegas region, and have gone through probably $100 easy in worms in the past year trying to raise worms;killing every colony until recently. I think that I have finally found a way that is working for me. I use plastic bins, my favorite cardboard media is the pressed paper beverage holders that Sbucks and other places use to allow you to take multiple beverages away. The key seems to be to find an area that allows even temperatures and protecting them from extremes. For me this turned out to be the garage. While the garage can get hot it generally does not approach the 110 degrees F that we get out of doors. I had a shady area of my yard that only got an hour of sunlight during the summer, but that was enough that all of my worms did an exodus or died in the bin even with an effort to keep the direct sun off of them. In doors was not an option since the fruit flies or fungus gnats mobbed the house. We still have a few indoors but not as many as when the bin was indoors. The plastic bins are not perfect but in this dry climate it holds onto the moisture in this dry climate. The biggest thing is to keep from over feeding the bin. Currently I have food visible on the top that is still breaking down, I stop feeding them, and the rest of the waste goes to the out door compost pile.

    • Bentley
    • February 10, 2011

    Hi Jim,
    Thanks for sharing your experience – very interesting indeed!

  1. I’ll add my two cents. I’m certainly not in the desert but this past summer got over 100 degrees multiple times. I have several worm bins under a second story deck. I cover the bins with burlap and wet the burlap down at least once a day, more often if I remember and am around. The wet burlap gives an evaporative cooling effect. I didn’t come up with this myself. Some of the older manuals about growing worms mention it. One more way to deal with the heat!

    • Doug
    • February 11, 2011

    My dad spent some time in the desert and had several worm bed barrels like our 55 gallon buried deep in the ground seemed to do just fine best if you find a shade tree of course or some other form of shade that sun gets bitter down in them parts

    • Craig Miller
    • February 11, 2011

    Looking at the environment (Reno) that Sierra Worm Farms faces, It seems the inground bins work well in a dry summer climate. the concrete blocks, along with an insulated top. I am just getting ready to move to an upper desert environment and was thinking of using the same style of bin for my garden.

    • Julie
    • February 11, 2011

    I’m not living in a hot arid area. I don’t pretend any of these would apply. These are just my observations from trying bins and trays in my basement in winter so much drier, where the humidity is down to 30%, according to my cheap cheap humidity reader thinggy.

    I’m not sure yet in what all situations, but I think cardboard dries out faster than newspaper. Or, it’s always too dry too fast, or too wet and smelly, and anaerobic.

    Maybe in this situation,if you don’t have access to compost or vermicompost material, add in a portion of sand and dirt to start up the bin, or on top, to cover the food scraps, so that it retains some humidity from that and from watering? Once the bin is a bit more mature, add vermicompost from down below on top?

    I’ve only tried cardboard in an open tray (in my basement in winter which gets really dry -for here around 30% humidity), but the 3 top inches are completely dry an hour after I wet it, and the bottom is soggy and anaerobic and smelling (but the worms love it, they all congregate in the very bottom of that tray in the wet soggy smelly area).

    Newspaper, on the other hand, in both open trays and closed plastic bins, seem to hold on to humidity. Except in the worm inn, in my basement, it dries in a very short time, no matter how much I wet it , and I gave up on the first 3-4 inches, it’s just crackly newspaper-concrete. Lower it’s still dry, but if I keep giving it food, it doesn’t seem too bad. If I stop putting food it dries up further down. I wet it thoroughly once in a while and hope that some water trickles underneath.

    Also, I had a plastic worm bin outside in the shade and somewhat protected area all spring/summer/fall (here in the great white north- so doesn’t apply to your temperatures). I didn’t add any more newspaper in there after the initial bedding, just put a large piece of cardboard to cover the food I was feeding, fed in grass clippings twice only, maybe some dried corn leaves, or dried plant stems, and left it unattended for long periods of time. I “unleveled” it, so it wouldn’t accumulate water , one side being very slightly lower than the other (mere millimeters, barely noticeable slope) Still, the worms would stay in the soggy wet part and not really go up to the somewhat drier spots… at least when I was looking. There were no holes in the bottom, so no water was lost that way. Lots of ventilation in the cover and top sides. The temps from night to day would vary from 30F to 60F in the fall or from 40F to 95F in spring/summer (and not vary many of those 95 – and a few days only pushed to 100F with humidity)

    • Julie
    • February 11, 2011

    another thought : check the classified ads offline or online (, craigslist, kijiji, or whatever you have there) for free worms from other wormers in your area…

    if you go pick them up, you can take a peek at their set-up, and ask questions pertaining to your specific climate….and maybe share back with us the particulars 🙂

    • Steve L.
    • February 11, 2011

    I’ve never had the problem with my worm bins “drying out at the speed of light”, but I wonder if you laid a sheet of heavy plastic (cut to the size of the worm bed) on top of the bedding that it would act as a vapor barrier and slow the evaporation. There would definitely be enough air pockets so the worms wouldn’t suffer that way, and I assume that the bin either has a lid or something that deflects direct sunlight. Maybe a damp t-shirt/rag/burlap covering directly on top of the bedding followed by the sheet of plastic would be a combination that’d work.

    Living in the Pacific Northwest (Portland, OR) I deal with the opposite extreme of having a high humidity, cool climate that forces me to deal with excessive moisture. In my plastic barrel FT bin I literally have not added additional moisture (like sprayed water) since October of last year. The moisture from the food and damp bedding I add, plus the insulating layer of dry leaves (12 inches worth) on top of the bedding seems to actually cause excessive condensation.

    • Jason
    • February 12, 2011

    On the vermicomposters blogs a discussion about wicking beds came up, and I wonder if this might be the answer to your problem.

    It might be worth a look at least.

  2. Hi all!

    We live in SE Arizona at an altitude of about 4100 feet. The temperatures here are cooler than Tucson and Phoenix, but it gets hot just the same. We have had humidity as low as 5%…in the summer.

    I have worms in three locations: two 18 gallon plastic totes in the office, an 18 gallon tote and a black footlocker on the patio and a windrow out in the horse’s “playpen”.

    The bedding in the office totes consists of shredded junk mail, newspaper, corrugated cardboard, and Pepsi containers. The worms in these container feast on food scraps. To keep the smell down and the flies away, we bury the scraps under several layers of papers. The worms LOVE it! We also “flip” the contents of the container every few days to keep everything on an even moisture level.

    The two containers on the patio have Euros in them. They feed strictly off horse poop. We thought we lost them all in the recent deep freeze we had, but inspection the other day revealed that most have lived.

    The compost worms in the windrow have enough room to move around to warm/cooler areas. When the top of the pile gets dried out, we set the water sprinkler on them for an hour or two. These guys, too, get straight horse poop.

    Hope this helps!

  3. I live in the high desert in Central Oregon and although our temperatures are colder we have many of the same dryness problems. For my outside bins i started using straw bales for the bounders and a good layer of straw on the top. I feed from one end and harvest from the other. A photo of my bin is on one of my web pages. and if anyone is interested I could post more. I have found that this has solved two problems. The first was moisture control. I just keep the straw on top moist and the rest takes care of itself. I do use lots of paper and straw as bedding but I think the insulation of the straw is what keeps the moisture in. It also help moderate the temperature inside the bin. We have hot summers, well over 100 F and cold winter nights,sometimes blow 0 F in the winter. Since I have started this I have had no problems with these bins. They just keep going and going as long as I keep feeding. Another problem it has solved for me is the pre-composting problem with heat. When I add material to the end, if it heats up the worms just stay away until the temperature is right for them and then they move in. It has been a great design for me.


    • Jackie
    • February 16, 2011

    I live in Phoenix, AZ and have had been successful raising worms both inside and outside (even in the summer!). The secret in the summer is deep shade and not overloading the bins with organic matter. I have three plastic bins semi-buried in a raised flower bed on the north side of the house, with styrofoam between the bins and the bricks for a bit of insulation. I always use a plastic “blanket” with holes poked in it on top of the bin material, in addition to the plastic lid which also has tiny holes in it. The raised flower bed is covered by wooden trap doors which provide some air circulation and additional shade. I use wet shredded newspaper as the main environment and, of course, add kitchen scraps. There are teeny tiny holes in the bottom of the plastic bins but I don’t think they are very successful at draining water from the boxes, as the bin material is always very, very wet. The worms seem to like it, though. I have also had success with worm bins that were not even partially buried and were placed under trees in deep shade — i.e. never received direct or even indirect sunlight.

    I have had problems with worm survival when I tried putting worm bins or worms themselves in my regular compost (I think it was too hot for them and not evenly moist), with worm beds that weren’t in deep shade, and with worm bins that were kept in the garage (it gets very hot in there in the summer – apparently much hotter than in Jim’s garage in the Mohave Desert).

    In the summer, I cut back on how much I feed the worms (I think they may become semi dormant?) and try do dry their environment out a bit, mostly by mixing dry shredded newspaper into their bin material to absorb some of the excess moisture and also by feeding them less wet fruit waste. If the worm box material is too wet or too full of very wet organic matter, in the summer here, the worms will cook in the hot moisture.

    • Dean Richardson
    • April 18, 2011

    I live in Miami, Florida, and am just getting started with worm farming. Last summer we had multiple days with a heat index of 105°. My research into worm farming said that the Indian blue worm (Perionyx excavatus) is the best worm for tropical environments because it stands up the best to heat. I sense that it is also a very despised worm in the worm farming community for various reasons, but wonder if it’s actually the best alternative for South Florida’s subtropical environment. Any thoughts or experiences with tropical worm farming anyone?

    • Teacher
    • January 7, 2014

    Hi Everyone,
    I’ve been reading all I can on composting with worms. I’m looking to try it as a class experiment for our school garden here in west Phoenix. We have an outdoor school garden in a semi-secure area but I’d rather not put anything out there that could be stollen or dumped by vandals. We also have a custodian closet I could house something in. However, it would have to be semi portable so I could move it out of the closet to work with the kids and transport it home over the summer.
    Does anyone have any recommendations on what I should build, how to build it, and how to keep the worms alive in the Phoenix heat? I’d rather not have to explain why all the worms were “sleeping” then just “ran away” to a classroom of curious elementary school students. I have a budget of $150.

    • Don Brown
    • February 23, 2015

    Try a walkway between your beds, dug out a couple of feet and filled with seasoned horse manure. Cover the walk way with straw and some tile stepping stones. Water the walk way as you do the garden. I have found the worms can migrate as they want, but the horse manure will be their home of choice if it has been seasoned by wetting it down until it stops heating and the interior of the manure is about ambient temp. When you stat the next crop, scoop out the worm casings into your growing area and refill the walkways.This works for me here in north Phoenix

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