Posted on

Making a heated propagator

I have to admit that in the past I have really struggled with germinating seeds. Some are fine and will romp away in almost any conditions, most brassicas for example just need to be shown a pot of damp compost and they’re growing away. Others like my Carolina Reaper chillies are are a lot more finicky when it comes to the conditions that they germinate in. Essentially if the conditions are right and the seed had had any preparation that it requires then a little bit of heat from below will get them going.

I decided then to make a heated propagator as the ones that were for sale at the size I wanted weren’t really an acceptable price, to be honest they’re really expensive. What I built was 1m x 0.5m and comes in at just over £40 and is essentially the same as you’ll get for 4 times that price. The main things that you need are the heating cable, some wood for the box and some sand to create base for the cable and to sit the plants on.

Heated propagator

What you’ll need

  • 2 side pieces 1m x 10cm (ish)
  • 2 end pieces 50cm x 10cm (ish)
  • 1 base 1m x 50cm x at least 10mm thick
  • 1 heating cable with themostat
  • 6 x 2″ galvanised nails
  • 18 or more 1.5″ wood screws
  • A drill and a 10mm wood bit

How to build it

Without going into specific places to acquire the wood from I’ll just say where I get things like this as there are plenty, I’m lucky to live in a city where resources are discarded liberally. The base just needs to be a flat 1 x 0.5m board of something like ply, if you have to buy it then any larger DIY shop will have this, make sure it’s at least 10mm thick though. I have an IKEA near by and they are frequently throwing out stuff like this. Be careful of MDF though as although it’s unlikely to get wet, there is a chance as you water the seedlings from above. Probably a thin coat of acrylic of varnish would solve that. For the sides I had some old engineered boards but a broken up pallet would actually be a really good substitute. The length of cable that you use us dependant on the size of the tray, you want the rows now more than 15cm apart so for mine a 4m length was sufficient. It’s better to have too much than too little.

Heated propagator corner detail

The construction is just a case of cutting everything to size and screwing it together, use screws not nails as you’ll most likely be moving this thing from place to place and when the sand is in it can be quite heavy.

Once the carcass of the propagator is made you need to get the cable in the right place, ideally right in the middle of the sand but there’s a really easy trick to getting this right, this is where the nails come into play as they will be what we use to hole the cable in place. Knock the nails into place as shown so that the heads are just below where you want the top of the sand to be but make sure that they don’t come through the bottom of the base. Drill a hole large enough to pass the cable through no higher than the top of the nails, preferably nearer the bottom.

Then you add the sand to half way up the nails and make it as level as possible. The nails should be sticking out of the top of the sand by a centimetre or two so that now you can wind the cable up and down around the nails using them to keep it all in place. Once the cable is all laid you just need to add more sand until the nail heads are just covered.

Heated propagator

That’s all there is to it although it will take a little while to put together but you get a solid, functional heated propagator. I’ve made a cover for mine using the same method that I used for the cloches. I’ll add a post about that soon as they’re another really good piece of kit that comes in at a fraction of the cost of retail versions. If you’ve any questions just ask, happy building.

Leave a Reply

Your email address will not be published. Required fields are marked *