Heat mat or heated propagator

[greenishfing]

I've never really used either but years ago I had some old electric heated sort of stainless steel trays for putting demi -johns of wine on and keeping warm when they were working ( bought in a job lot at a car boot sale). I discovered they were great for propagating tomatoes and chillies. I don't know what happened to them.

[Logunner]

My heated propagators would struggle at those temps winter / early spring. They aren't very powerful. 13watt I think so capable on maintaining temps maybe 10c above ambient but defo not 20c+ needed for chillis. You can get fancy temp controlled ones tho that maybe more powerful.

No chillies, so all good.

[Babru]

I was interested to see this thread, as I have a heated propagator I haven't used for a few years. With my new garden I have lots of space to fill, and plan to be sowing annual and perennial flowers so I don't need to buy much.

Last year I successfully sowed cosmos, verbena, French marigolds, pansies and wallflowers, just using pots with a plastic bag over the top. Will I get better results using a propagator? Are there some seeds that I really need to use it for? I lifted dahlias, a canna and scented cosmos, should I sit their pots on the propagator as I start them off?

Sorry for the long list of Q's......

[bramble]

You would need some type of heating if you are growing chillis, tomatoes or peppers.
Wallflowers are seen outdoors in the open ground and will germinate without any heat.
The rest of the flower seeds should also be fine without heat.

[bramble]

I have 2 propogators which I use to start off my tomatoes and peppers every year.
Dont have a heat cable and never felt the need for one.

[ESBkevin]

We have two propogators, one double the size of the other standard sized one. The smaller one is a few years old now and does nearly everything, the larger one will take a few pots once things are potted on, but we use an LED grow light in a spare bedroom which has ambient warmth once things show through.

[mrbadexample]

Normally I use this little plastic propagator inside, placed on top of a vivarium heat mat. It functions perfectly well, but is small.



I was given this last year (too late to use it), and I'd like to start using it if possible.



But I don't really get how it works. There's no lid. If I put it in the greenhouse, it's -2�C at night at the moment - will it cope? I haven't got room for it in the house.

Any advice getting this thing up and running would be appreciated.

[quanglewangle]

I use a home made propagator made from a plastic tray about 500mm * 1000mm by 50mm deep. It is filled with sharp sand and has a 50W heater cable embedded in the sand. It is important to keep the sand very moist to give good heat conductivity. The temperature is controlled by a small computer from a probe in one of the pots. You don't have to use a computer - a thermostat will do. It's just that I control lots of other things (such as heated beds) and thermostats and timers get expensive when you have a lot of them.

I aim for IP44 Ingress Protection. Exposed metal is earth bonded and the whole greenhouse is behind an RCP


Propagator - without its fleece tent

It is very heavy: about 30 odd kg sand and 10l water.

Once seed starting off is out of the way I use it for three 30cm pots with auberines and a couple of smaller pots for chilies and it seems very successful. The roots spread right out of the pots into the sand. I replace the sand each year.


Oops - mistake. The green lines below refer to a bed not the propagator, which is not currently recorded but runs about 18�C
Here are the sort of temperatures I get with 50W - blue is the air temperature in the greenhouse and green is the temperature in the bed. This is with the fleece tent in place. Lowest air temp in greenhouse so far has been about 2 �C and lowest in-pot temp about 10 �C. Last few days have been clear so big diurnal variations in temperature.


Temperature over last few days. Blue greenhouse air. Green [s]in-pot[/s] in-bed compost

[Babru]

Wow, quangle, I bet the moon landing wasn't as well organised as this.

[quanglewangle]

Wow, quangle, I bet the moon landing wasn't as well organised as this.

I grow stuff too

[Can the Man]

Seems very complicated for the amateur gardener Quangle, I bet you work in electronics or automation industry.

[quanglewangle]

Seems very complicated for the amateur gardener Quangle, I bet you work in electronics or automation industry.

Yes, I am quite interested in the way commercial growers operate and, by training, I am averse to wheel re-invention.

I used to design and program low level stuff - down where the actual binary bits live. Retirement process took some years and involved a spell teaching undergraduates. Now there is no-one, apart from Mrs quanglewangle, to frown at me when I pick up a soldering iron.

[Logunner]

Is

low level stuff

code for I was a �spook� at GCHQ?

[mrbadexample]

I've stripped out the old lining which was brittle and nasty, so I know I need to re-line it.

I've got plenty of sand - what depth does it need please?

How deep should the cable be buried? Should it be on the bottom of the box?

Please assist, if you know what you're doing.

[quanglewangle]

[ATTACH=CONFIG]89814[/ATTACH]

I've stripped out the old lining which was brittle and nasty, so I know I need to re-line it.

I've got plenty of sand - what depth does it need please?

How deep should the cable be buried? Should it be on the bottom of the box?

Please assist, if you know what you're doing.

"If you know what you are doing" That would be a first for me, but here is advice anyway.

It's worth standing the propagator on some insulation board. I know theory says not much heat should go downwards, but I found it made a difference. Off-cuts can be scrounged from building sites.

Depth of sand: remember purpose of sand is to even out heat distribution; to provide some "thermal ballast" so temperature doesn't vary to much; and support the pots. You don't need any more than will achieve that. Mine is about 40mm deep.

How deep should cable be? Mine is about 2/3 the depth of the sand. I would be worried about putting it on the very bottom, since you want the heat to go up.

Remember to keep it very moist. It's the water that conducts the heat not the sand.

Don't over think it. It will be fine.