Heated Propagation bench/Table

For Winter / Spring I do it indoors, under lights. Not enough light for growing well in greenhouse during the winter, and a greenhouse structure is thermally pants! and thus very expensive to heat (although soil-warming means lower air temperatures are fine). I just use a warming mat to stand seed trays on etc. (thermostatically controlled with a temperature probe in a pot, on the mat, to actually control according to the temperature of the soil rather than mat / air temperature), lights over the top, in my home-office, which I reckon is cheaper than trying to heat my greenhouse (and it still wouldn't have enough light in Winter)

In Summer I have a mist propagator in my greenhouse. Its under the bench, so the cuttings are shaded, and as such no "bench". Everything I try to strike seems to root just fine, so I haven't bothered with soil warming, but that's probably only because the things I grow maybe don't need it / would root faster if I had it? But the key for me is the mist. I have no idea why mist controllers are so expensive I Um'd and Ah'd for years before buying one - bad decision, I should have bought one years ago it would have saved a fortune on propagation! Mine is hooked up to a pipe that runs under the staging all around my greenhouse with misting valves at intervals - and also taps/valves at various points so I can use just part or all of it, thus the cost of the controller is offset, somewhat, by having a long length of misting pipe / nozzles.

Anyway, back to your project: you need to heat a bed of sand, that "bed" has to be moist and of sufficient depth to hold and spread heat, that's where the 6" deep is coming from. 6" depth of moist sand weight a lot!, so you need a strong structure (or put it on the ground?). I expect you also need a transparent cover to retain humidity / heat, although you might use individual pots/trays that have their own transparent covers? (but that won't stop the sand drying out, so personally I would favour an "enclosure" over the bed - even if it is just hoops with a plastic sheet draped over the top, like a cloche.)

I made one a few years back .out of odds and ends of scrap wood. Bought an undersoil heating cable and a thermostat and a couple of bags of sharp sand. It worked really well but it always irked me that my seed trays didn't fit exactly into the space available. last year, I re-arranged my shed and demolished the heated bed. Bought new materials for the framing and bottom and made a new structure( including legs ) in which my seed trays now fit exactly. I lined it with heavy gauge polythene before putting in the sand and the thermostat then put in another layer of polythene above the sand to keep it from drying out. Topped it off with capillary matting

Cheers! For replies!

It's just I have a "Flat Packed" wooden greenhouse stashed in the garage which I was hoping to Knock up this last year! But never materialised! Work commitments, n trying to keep on top of the plot! You know how it is Eh!

But if I is gunna do this! I want it to be right, with the whole "Kit n co-boodle"

Heated bench, potting table, heater etc! etc! You get the idea!

Just fishing for idea's!

I have a plan! I think!

In relation to Kristens' reply, I am a little confused as to why the sand has to be damp as the trays will have medium in them. Does damp sand retain heat better than dry sand?

Damp sand conducts heat better, so it will spread the heat around (and up to the seed trays) better

Cheers Martin.

Well I never knew that....just goes to show no age limit to learning

To counteract the weight problem, I wonder if damp Vermiculite will have the same result or will it dry out too quick.

Put another way: dry sand is an insulator, so the heat won't spread and, I believe?, that can cause the heating cable to overheat and burn out

BM! Your on my "Wave length"

But yeah! Because of air pockets etc n it's pure lightness! It doesn't hold moisture!

Vermiculite does hold water. Perlite on the other hand doesn't.

It's been a long day! Just remembering brown stuff does!

White stuff doesn't!

Edit! It doesn't "Retain Moisture" for a period of time if not mixed with medium!

Well! That's what I've found!

As Santa been yet? can I Call it a day?

That's one way of putting in Deano...................

Deano if you are thinking of mixing vermiculite with a combustible medium ie. peat for example I would recommend that you keep it moist at all times or it could ignite, I have seen a fire that started with a heat cable in a bed of peat. The top of the box and wooden frame of the greenhouse was burnt the glass cracked with the heat but the cable was still usable