Heated seed beds?

Hi everyone, I'm just mulling over the idea of making some heated sand beds for propagation next year, I know some of you have built them so I'm just wondering if it would be worth it for me? I've googled how to make them so don't see any problem there, Size is only 5ft x 21" and would split into 2 or 3 beds with thermostats if that was felt necessary, I can't say how much seed I will be growing but I've used two propagators this year, honest opinions please.

 

I use both. Props where I'm fighting cold nights in the polytunnel. They tend to stay a bit warmer.

I've switched the heated bed on again this week to encourage some tropical seeds on. It seems to have worked as the strelitzia seeds have shown their faces. The heated bed also acts as a bit of a storage heater when the weather is warmer, smoothing out the temperature difference at night.

If you build a heated bed I would use only one thermostat but buy a decent one. The cheap ones don't last in my experience. The cost of three stats would outweigh the savings for quite some years and I find that I fill mine very easily, meaning that I need to heat all of the bed. I did install two heater cables and have them both powered when heating - just a bit of a fail safe for cold nights.

 

Thanks @andrews

 

What I have found is you can use 2 or 3 seed tray sized little electric props for germinating seeds and rooting cuttings and then a larger area like your bench with a heating cable at a lower temp for growing both on / keeping them frost free.

I use digital thermostats (diy) for all of them as the little props can easily overheat even in the winter sun.

Did try heated sand beds a long time ago, too damp in my experience; now just set up a bench with an insulating 25mm sheet of polystyrene with a layer of strong foil on top to reflect the heat and light and just lay a heating cable on top of it, pinning it down with a few cable clips etc.

If you want a high temp in there, then a constructed closed structure is needed, but I just use one of those cheap mini greenhouses 4x2ft £10 from Wilko, which also serve as a hardening off frame outside later on.

Have a little remote display in the house so I can see whats going on in the really bad weather.

 

Thanks @ricky101

 

Hi mazambo,

Did you go ahead with the heated seed bed. I am pondering whether to make be for next year. Wife I not happy about me using windowsill in front room after we have had the work done n the house. So need to find a new gear source for heat loving plants to germinate. No sure whether this is a go or heated prop. Need to eat up costs.
Rusty

 

No decided against it, it's a good idea but I need flexibility in the greenhouse because it's only 7'x 6', so I went for heat pads and heated propagators.

 

[QUOTE="rustyroots, post: 1254079, member: 10199"

I am pondering whether to make be for next year. Wife I not happy about me using windowsill in front room after we have had the work done n the house. So need to find a new gear source for heat loving plants to germinate. No sure whether this is a go or heated prop. Need to eat up costs.
Rusty[/QUOTE]

You can use heating pads and the small heated propagators, though they might be costly, but if you use a larger heating cable they usualy show them buried in a heavy sand bed, but for years I have used this cable just on top of a board and insulation so when the plants are big enough the simple bench is removed and the space used to toms etc.

An adjustable thermostat is very handy

The 4x2ft cover( £10 Wilco) is then used as a cold frame to harden off the bedding plants.

 

Thanks both. I have been looking into it tonight. I think there is more flexibility in using a couple of heat mats. I presume that there is no difference in a reptile mat as these are half the price of ones found on gardening websites etc? I need to put electric into the GH, which I was planning anyway. And during clearing out garage found the armoured cable I was planning to use. Just need the sparky to be able to do it, which won’t be anytime soon.

Rusty

 

Nothing to stop you laying the armoured cable, thats the hard part, just get the electrician to do the final connections.
Good time to lay a water pipe if you do not already have a supply ?

Never used the heating mats, but looking at some of them, some do carry a notice not to immerse in water, so not sure how suitable they are for a greenhouse where its so easy to spill water ?

Also they seem very low wattage so probably only suitable for small seed tray gentle heating ...?

 

I have that problem too. Replace wife? Pretty sure I could find someone on GC much more in tune with how windowsill plant raising is a basic requirement of living ...

Although, I have got a suggestion of sorts. I have a "shelf unit" in the boiler room with LED lights. Much better than either windowsill or heated greenhouse, 'coz early in the year the natural light is very variable - some early Springs it is permanently overcast and lousy for growing. Other times very bright and lifts the temperatures significantly and makes the plants grow too fast.

I agree, I have always done that grunt work in the past. Sparky might want the trench left open for their inspection and sign off on Part-P or whatever it is called (probably depends on whether you know the Sparky )

I highly recommend putting in a bigger cable than you need ... the extra cost is minimal, but by comparison digging a new trench and putting in an extra cable is a big job. I did a calculation for the AMPs I needed and volt-drop on the run, and bought that sized cable. It copes with a 3kW fan heater, but it wasn't spec'd for that, so is probably not really suitable and may well cause me problems (or is possibly costing me money in "efficiency loss"). I also wish I had put in 4-core rather than 3-core which would allow for two circuits, e.g. one permanently on and one switched-from-the-house - for any after-thoughts - like garden lighting.

Or a duct with a pull-cable (and the actual cable)

Good idea Again I would go for bigger size. Unless it is only a few feet the flow rate will be better with more diameter; Wastes a lot of time, over the years and decades!, waiting for a watering can to fill up on a piddly 1/2" supply pipe. I put 32mm MDPE in.

 

Get a new wife . I don’t think anyone else would put up with me.

I will run cable as I need to take up path to lay. It is only about a meter or so from shed, so not a big deal. I already have water down there, so that’s OK. I think so have about 4m of armoured cable so will drop it in and then sparky can cut off what is not needed. I need him in anyway when lock down is over so will get him to have a look. I presume he can just spur off the circuit in the shed
:confused: .

The more I am looking into it the more confused and unsure I am. Now I am thinking of using a cable and making a bed with vermiculite. I have all the timber for frame, PIR insulation board, vermiculite and waterproof membrane. I can then use vermiculite for something else or store for following year as Incan with table/box construction. Just need cable and thermostat. I have made a deal with wife that this is the last year to use windowsill, so have a while to decide and construct.

Rusty

 

That would be my snag too. I haven't had any offers from here either, so clearly I got that wrong too ...

Worth a phone call to ask? I think it might depend on the capacity (and length) of the cable-to-shed.

Back when I worked on a propagation nursery they had beds of Perlite (and Mist). Can't remember about in-bed heating, but they only did propagation in Summer, so probably not ... We just took cuttings straight into the Perlite ... potted them on, piled the Perlite up over steel steam pipes, covered with tarpaulin, steam-sterilised, and then rinse-and-repeat

No help for seed raising though ... the old boys up on the allotment used to have a Paraffin stove under a metal bench. Which was fine until they trimmed the wick wrongly and arrived the following morning to find absolutely everything covered in soot!

 

When you lay the cable underground , use some 40mm waste pipe or similar to run the cable though, that allows you to easily add or remove any other cables etc.

Is vermiculite good for using around a heating cable, would it act more as an insulator rather that distrubuting the heat ?

The reason we stopped using a sand bed is that lots of things damped off too easily. Such a moist environment is good for certain propagation but not everything.

 

I use two 20x48" heating mats. Each has their own temperature controller. They are under felt which in turn draws water from a water receptacle and provides capillary irrigation. It has worked well now for the past 4 or so years. The seedlings seem very happy and I keep the lights almost on top of them and raise them as needed. When the plants get too big for indoors or I feel they are ready for hardening off, they go out in the heated (low 53f) greenhouse. There is capillary irrigation set up in there too so the plants don't have their drink cycle disturbed.

The heated mats made a huge difference at the beginning of the plant's growing cycle. I started with lots of those 10x20" mats but got a little fed up with the number of cords so that is when I bought the bigger ones to mostly cover each indoor surface. I still have the smaller mats and they still work and I never had any issues with water- they always sat under a wet piece of felt. I'm trying to think of some other purpose for them but just can't - suggestions would be great if anyone has a practical idea, I'd be glad of it