Hay bale garden - temperature and mold questions

I acquired 5 hay bales a few months ago that had some mold.  I placed them in a square and filled the center with compost and soil.  I am planting in the center and also placed some soil and seedlings and seeds directly in the bales (straw bale garden concept iwth hay bales).  I live in a super cold climate (zone 3a) so the added warmth is good, EXCEPT the temperature of soil where I have planted measured at 78 degrees yesterday.  The air temperature has not gone above 65 year to date, and it snowed 5" just 4 days ago and has been in the low 30s at night.  Is there some sort of decomposition that might be going on to result in such high temps?  I have Chinese Cabbage and chard planted that are not doing very well!!  Although carrot and radish seeds are germinating.  For reference, the soil temp in the compost/soil filled center area is about 60 degrees.  The soil temp of the traditional raised bed next to the hay bales is 54 and the ground temp is 50.  Thoughts?  Should I be worried?  Or just plant bananas?
Also, should I be worried about the mold?  THey don't really smell like mold, but it's been a really wet spring and the sides of the bales look kind of dark.  Can I get sick from eating food grown in the bales?  Photos attached.  Thank you!

Your hay bales are composting.  Hay has a good ratio of greens/carbon to compost.  Don't be surprised if the interior temperature of the bales gets 120 or 130 degrees.  It won't stay that high for very long.  I have to keep turning my piles to keep them hot.  After a few days without turning, they will cool down.  If you can, you can also water them often.  Watering cools compost temporarily.

Yeah, those temps indicate active composting, which is the plan.


Tomato plants would love that heat.  If you have a way of putting hoops over the bed, or a part of the bed, and sheer curtains or greenhouse plastic, you'd have yourself a mini greenhouse.


The only thing about the mold is if you get it on the greens, be sure to wash the greens thoroughly before eating.  Just like if we use compost with manure in it, we don't want that good soil bacteria on the greens we eat.  Try not to let wate,r that would probably contain mold/bacteria, splash up into the greens, like lettuce or cabbage heads forming.  You can avoid that by putting soil over the top of the bale and under the greens growing there, or just use drippers.

No reason for concern.  Bales can also be used for heat during the winter in a greenhouse  or high tunnel.  I regularly pack straw from bedding into my raised beds.  They are great for potatoes and other root crops.  If you get hooked on using them, post Halloween haunted houseware a good source ... or so I have found.  Also, if you continue to use them, they will eventually compost enough to fall apart.  If you build sides around them, you will better be able to contain the composted material.

Thank you everyone!