Advice and tips on heat mats in green house

Looking to propogate in greenhouse ( as opposed to indoors - poor light) in early Spring. I want to buy a heat mat. Any recommendations? tips on propogating? Also bit nervous about extension lead into greenhouse. I have outside plug sockets in garden but not in greenhouse - any advice?
Thanks, as always.

 

I only have one thing to contribute.
Get a mat or a propagator with a thermostat. The cheaper un-thermostated type heat all the time to about 10ºC above ambient, which is too cold on cold days and too warm on warm days. The thermostat (to state the obvious) keeps the temperature more stable.

 

Is the house with a grow light an option anyone employs?

 

I think heat mats are great. When I had a GH at my old house OH rigged up an extension lead to a socket in the garage. He attached the lead to fence posts above head height so it wouldn't be in the way or get damaged. The cable went through the window in the roof which was never fully shut for a bit of ventilation. I had a socket board inside the GH so I could plug in the heat mat and 3 electric propagaters. It kept the GH frost free and I was able to grow masses of plants from seed which saved a lot of money.

 

I use a propagator box I made years ago using a soil warming cable covered with sand.
I agree whatever you use you need a thermostat.

 

You do not say what scale of propogation you are looking to do and if its from cuttings and / or Seeds ? Just smaller plants like Pelagonium or Fuchsia cuttings etc ?

We tend to use a couple of the full size electric seed tray ones but with a thermostat as once they are well rooted / seeds germinated you need to reduce the heat or move them to somewhere cooler.
For that we have a heating cable (or mat) , again with an adjustable thermostat , on the greenhouse bench, but use a polythene or bubble wrap cover on that whole area to keep the heat in.

How far from the outdoor socket is the greenhouse ?

 

I thought it worth having armoured cable installed on a separate spur, with splash resistant sockets in the greenhouse. That way I can heat it, or power a thermostatic propagator etc.

 

DiggersJo. I use one as part of a unit attached to a plastic water tray with a capillary mat tray fitted above. Electric plug attached to a timer plug as I do not trust inbuilt thermostat controls as one broke and fried all my seedlings.

 

And in this day and age don't waste money on a mechanical timer for the socket end...get a WiFi enabled one so you can switch off power on warm days from your phone. And you can schedule it according to need and conditions and some of them will even monitor the energy consumption.

 

What is WiFi?

 

@MrHappyDays how are you getting on with your heat mats?

I’m very new to gardening but I’m loving it. I have a glass structure at the end of my garage - not technically a greenhouse but serves a similar purpose. I want to start off with my seeds. My greenhouse gets a lot of full sun, so is really warm during the day, but still gets really good at night.

I was considering putting heat mats under my seed trays and putting them on overnight.
Any tips from anyone?

 

Hi @Novice Gardener Laura it depends on how much light you've got as to whether it's worth more than just frost free. Otherwise things will grow straggly. And I always put a thick sheet of expanded polystyrene under my heat mats so that they're only heating the trays! For heat mats on house windowsill, I just use the thermostat they came with. For heat in the greenhouse, I use an Inkbird controller as it seems more robust.

 

Your target is to be able to maintain the correct temperature for germination 24/7. This requires ideally a heat source and a thermostat, such as the Inkbird*. This can be as described above, that is with insulation and heat mat. An enclosure (lid) to retain the heat, maintain humidity and admit light. Need to check daily.
The next level would be to build a heat bed , using an undersoil cable and a bed of moist sand, to stabilise the temperature chosen , avoiding shocks such as cold draughts.This can be run on Inkbird too (1 for each heater)
Once your seeds germinate, generally they require constant but lower temperatures in good light to grow steadily.This could be using the heat bed, which can also be used for later sowings once ambient temperatures occur in later Spring.
It is this stage that makes or breaks the plan, sowing too early and then not having the facility to grow on. (kind of like bed blocking in the NHS !)
*Inkbird Prewired 230V Temperarure Controller Thermostats Waterproof Rubber Probe | eBay

 

Thanks @CarolineL
The “greenhouse” is definitely frost free inside, even in snow. It’s attached to the garage on one wall and has a proper roof, so it’s just 3 sides glass.

It gets full sun, so gets really warm during the day. For example today the compost is warm to the touch.
I’m just curious if a severe up-then-down in temperature is detrimental, hence why I thought using a heat mat at night.

 

Thanks
@infradig
I think you’ve clarified what I was worried about with rise/fall in temperature.