A hot bed experiment.

Read on to find out what's going on here...

I have a perennial problem. But I'm not talking nettles, dock or dandelions. It's the problem which is perennial.

For every year I am itching to start off my first seeds, as is every other keen gardener. But patience is required. For there's no point putting time and love into germinating trays of seedlings if there's nowhere for them to go. There's a good 10 weeks yet before we reach that all important frost-free date and we can't let ourselves get fooled by the absurdly mild winter we've had thus far. After all, it was only two years ago that we had a severe frost in early May which really did a lot of damage.

To some extent, I can bring this May date forward at least a month by using the polytunnel as an interim home for young plants. But if only I could find a way to bring it even further forward without going to the expense of heating a greenhouse or building a conservatory!
An extra three or four weeks would make such a massive difference to those exotic crops which normally grow in the tunnel, the peppers, tomatoes, aubergines and chillies. Germinating the seeds indoors is no real problem, but it's the next bit which is rife with difficulties, raising the seedlings. For, to be honest, there's not really anywhere in the house which is warm enough, light enough or airy enough for such delicate young plants. The polytunnel is tempting and will probably keep the frost at bay, especially if I watch the night-time temperatures carefully, armed with fleece and bubble wrap. But it won't give them the sort of temperature they really need, not for a good few weeks yet.

But I have a cunning plan! A HOTBED.
Free heat in the polytunnel, powered by bacteria, the sort which can raise the temperature of a compost heap to scalding. I don't know how well it will work, so my early sowings will have to act as guinea pigs for this year.

 

I've been reading this book and discovered that it is perfectly possible to be producing a whole range of crops outside even at this time of the year. All you need is mountains of horse manure, forests of scrap wood and quite a bit of glass. It was all the rage in times gone by - times gone by when horses were more widely kept and the world hadn't yet ran out of raw materials. I guess it could be scaled down a bit, but you still need a lot of manure. This does not quite sound like the system for me, but the theory is a good one.


It's amazing how the deep litter builds up.
Clearing it out is quite a job.

And so I resolved to experiment with building a hotbed in the polytunnel over which to raise my delicate seedlings. I managed to source some scaffold boards very locally, so all I needed now was some poo and used straw. I don't know whether it will work quite so well, but it was time to clear out the deep litter from my goose stable. I figured that this straw, mixed in with the bags of horse manure which I regularly collect, plus a couple of bags of leaf litter which have been sitting outside, should hopefully do the job nicely. I dug the bed out to a depth of about 9" before proceeding to fill it back up with my mixture. I actually don't want it to heat up too quickly, as it will not keep its temperature. I am hoping for a gentle heat within the soil which covers the heap.
An outdoor hotbed would be covered with lights (frames of glass or plastic) to limit the amount of air space which would need heating and to provide insulation to keep the heat in the soil.
My idea is to place those cheap plastic 'greenhouses' over the hotbed. It's a large airspace, but I'm hoping that inside the polytunnel this arrangement will do the trick.

If it works, I might finally get my aubergines to ripen properly, I might get ripe tomatoes when all the other salad crops are ready and my peppers might thrive rather than limping through the year.
The added benefit is that I should have a warm bed, full of nutrients to grow crops in once the seedlings have moved on. This will be my raised bed next year and the hotbed will be rebuilt on the other side of the polytunnel... if it works, that is!

The first layer

Building up the hotbed

The soil goes back on top

I constructed this raised bed too. This will be next year's hotbed.

I still had too much straw from the goose stable,
so I mulched this bed which I will use for pumpkins this year

And the geese have a nice, clean stable.