One Word: Hotbeds



I spoke at the Connecticut Horticultural Society's monthly meeting last night  Lovely people. And definitely one of those situations where I learned more from them than they learned from me.

At the end of my talk, which revolved around soil management, with detours into parasitic worms, sanitary conditions in military camps and cow manure, a distinguished gentleman stood up.  I asked later, and he was David Smith, the retired longtime horticulture director of White Flower Farm.  

He said I'd reminded him of something from his childhood. His father was head gardener on a British estate. And they'd used piles of manure and straw to create hotbeds. 

These hotbeds were basically cold frames set up on a bit on fine soil over a compost pile.  They'd seed tender vegetables in them, and the heat generated by the composting process would protect them.

As he was talking, a vision flashed before my eyes: melons. The great frustration of my gardening life.  Almost impossible to grow in Zone 4.  You can't start them more than a few weeks early indoors, or the plants start vining around your lamps.  They sulk when stuck into the garden in early June and will disappear entirely after a cold, rainy night or two.  The plants are healthier when direct-seeded.  But then the fruit fails to ripen before it gets cold again.

And such a delightfully low-tech solution!  Using a free energy source provided by the soil microbes!  So perfect for a minimalist gardener like me! 

I have to try a hotbed or two in spring.  Of course, I've read about hotbeds before, but sometimes you just need to hear from somebody who has seen it done.

Photo credit: Bill Ebbesen


  1. I believe Will Allen of Growing Power heats a huge greenhouse with a long compost bed running down the middle and he’s up there in the far north. I don’t think it gets hot enough for mellons but it should work as a head start.

  2. It’s the poor man’s version of how the Japanese produce their obnoxiously overpriced yubari melons. Pretty good if you’re confident with the manure’s lack of pathogens.

  3. Here are some Cooperative Extension publications for building hot beds and cold frames. And as Kaviani noted above, fresh manures (necessary for the heat generation) can harbor pathogens like e coli and salmonella, so be careful when handling and be sure to follow the directions:

    As the publications note, if you want to avoid all risk, or don’t have a free large source of fresh manure, you can heat with electricity (less work excavating, as well.)

  4. Michele,
    You are far too modest–we learned quite a bit from you last night. I was at your talk and your command of soil mycorrhyzia was impressive!

  5. We had hot beds and cold frames at the Arnold Arboretum when I was an horticultural intern. The AA wasn’t using them so I took the opportunity to do several planting experiments with them. I remember having a challenging time with early damping off and later with mold fungus. I finally figured out good ventilation was required along with keeping the temperature within a average range. Some of the boxes heated up way too much with solar gain.
    I loved having the opportunity of this experiment and remember my first complete failure crop of primula vialli.
    Hope you have better beginners luck than I. enjoy!

  6. Do you think coffee grounds & leaves or pine needles would work as a substitute for manure & straw? Those things are much more easily obtainable in a city than straw and manure, and are safer and easier to handle.

  7. I wonder if a small solar water heating system could simulate the same thing, without any manure pathogens. Something like solar heated water tank-> piped to tubes under the melon soil -> piped back to the solar heated water tank. A small water pump would do it, perhaps even solar powered. Ever turned on a hose that’s been sitting in the sun for a while? The water gets HOT. 🙂

  8. I went to a talk on hotbeds in Colonial times – specifically Williamsburg VA and what has been excavated and shown what they grew over winter months. A lot of lost knowledge, I’m afraid, in this age of cheap gas and intl transport of food is easier than growing local. When gas gets to $10 a gallon, more of these practices will be brought back.

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