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Heated seed propagation

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    I’m about to embark on building my own greenhouse, using PVC pipe – well so the theory goes. Anyway as part of the design of the greenhouse, I’d like to put in a heated propagation bed, so I can take winter cuttings of plants and grow seeds so I can get a head start on the short growing season here in the ACT.

    I’ve been reading a lot of articles on the web about using hot water bed heaters, reptile heaters, rope lights et al, instead of actual propagation mats (which cost a fortune).

    Wondering if anyone has any experience in this area, or can offer any advice.

    I’m happy to post pictures, costs etc of my adventures with the greenhouse to share the knowledge if anyone is interested.


    Grr.. I replied to this an hour ago .. no idea where it went…

    Hi Evergreen,

    I’m currently a volunteer at Ceres here in Victoria, in the Propagation Department. I will gladly ask a few question, and pass on what I learn. 🙂


    Hi Evergreen. I bought one of the 4-flats heated propogation trays after using hot water bottles, cloches etc for years. Think it cost about $150, but I use it to start seeds for market sales, so totally justified 😉 .

    The best (pre electric) system was a hot water bottle inside a foam box with a glass cover for daylight solar heating, this meant I only filled the hottie at night. They did get quite warm with direct sun and I cooked a couple of trays on hot days, so learned to leave a gap for heat to escape and move into shade after they warmed in morning sun.


    We got hold of some fresh horse manure mixed it with some straw

    waited 4 or 5 days for decomposition to begin put a couple of inches of dirt on top then put seed trays on top

    this is how it was done pre electricity (check out Victorian Kitchen Garden series)

    cheap, easy and reliable (not subject to power failures)



    I’d a two flat heated one that lasted for 15years. it more than paid for itself over that time. I was without it for 2 years as I was too broke to replace it, my success with fiddly seeds and getting cuttings to strike plummeted. That said Dad used to sit his on top of the hot water service with quite a bit of success.


    Thanks ever so much for your replies.

    I have an instant gas hot water service, so unfortunately can’t use that.

    I have heard of the manure heatbeds before… Now I’m thinking about setting up a trial manure v rope lighting and compare germination rates – because to be honest, I’d much rather use manure than electricity to heat seedlings.

    Now I just need to make a base to put the seeds/cuttings in.


    So I completed my heat bed. I cheated and used outdoor rope lights (non LED) as the heating element that was embedded in sand, covered with black plastic. Old dripper hose was arched over, held in place with galvanised brackets. Over the top of this I draped some plastic that was wrapped around a mattress we bought a year or so ago (waiting for proper greenhouse material – when I can afford it). Although the heavy duty plastic is doing the job quite nicely.

    I did watch a you tube video on building a raised bed and filling it with horse manure, and putting soil on top of that and planting in that.

    My plan will be to set up a greenhouse (made out of Pvc pipe) and perhaps organise the horse manure to heat the beds – but that’s a long way down the track at the moment.



    I used to live in ACT and I discovered that reptile mats are much cheaper than propagation mats.


    Another cheap option is to use an aquarium heater (I bought mine for $12 on ebay) submerge in a large plastic container of water and put your seedling trays on top. Works well


    Finished mine. Multilevel benches for starting seeds.

    Fluoro tubes (warm white + cool white together as tube choice)

    Timer turns lights on/off on 12 hour cycle

    Heating controller for adapted from beer making turns the heat unit on/off at 21.1C

    Heat unit is a single bed electric blanket given to me for free by a co-worker

    Barrier seal thick plastic from Bunnings in concrete section water proofs (small thin roll of it covers the shelf width and length)

    Shelves are interior doors, two of them laying around the property

    Easy as and really good reuse of previous materials. Expense was really only 2 modern dual tube no ballast lights from electrical contractor (for modern energy efficient ballasts – never it from Bunnings as they have ancient choke starters that flicker when you turn them on and use more electricity to run) $45 ea.

    Everything else except $12 for roll of plastic barrier seal I had laying around.


    Photos, PeterD?

    I’ve got a 300W waterbed heater, but I don’t know if I can justify the price in electricity and space to keep something like that going. Have you considered that cost?

    And the 12/12 cycle induces flowering in some plants. Would a 18/6 cycle be better for vegetative growth, thus striking?


    This is just the first go so I’ll dial in the settings as I go. I wanted longer hours as the energy in the lights is it as high as sunlight. It’s only for a few weeks of seedling growth max before out potting to outdoors so I’m not worried about flowering as I’m it growing under lights for the entire life of the plant.

    I have photos but they are on my phone and I am not sure if I can get them up soon as I still have half the forum cut off on my screen issue with ALS.

    I’m germinating in the dark as light has not much of any influence over the majority of D70 vegetable seeds.

    I’m doing a new method from the USDA germination experiments book so fingers crossed.


    I will have to get photos organised but a report on running this incubator.

    Success! Well so far.

    Bel sent me some of her ironbark seeds. In 2 days all germinated except 3 and were potted on. The rest I started on Sunday and by Thursday I had filled over 180 seedling pots in trays. Mostly beans (in the high 90’s % germination rate) corn (in the high 90’s % germination rate) and tomatoes (in the high 90’s germination rate). Brussels sprout needed low temperatures and I’m running 24C-26C fluctuating temps but they germinated about 26% and seeing as I had hundreds I got all my early germinators potted and put the rest under soil outside to survive on their own if they will.

    So far loving it. Power is only temporarily on/off as it keeps heat in a zone range and no lights running yet as germination is in the dark for most seeds.

    I’ve also had trees like carob (in the high 90’s % germination rate) but most of my bushes are yet to germinate along with

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