Grow mat with thermostat for vegetable seed raising

Forums › Home Workshop DIY › Grow mat with thermostat for vegetable seed raising - maybe grow lights too

timmmay

15389 posts

Uber Geek

Trusted

Subscriber

# 180724 19-Sep-2015 12:37

I like to raise my own plants from seeds. Some seeds like tomatoes sprout really easily in a little portable plastic greenhouse on a windowsill, but others like capsicum and jalapenos take a lot more heat to get the seeds sprouted and then want lots of light.

Are there any reasonably priced grow mats around that can keep seeds around a selectable fixed temperature? Most seem to say "no thermostat, fixed at 20 degrees" or similar, but for capsicum/peppers you want more like 30 degrees. I'd rather have a thermostat based one, so it's not too cold and not cooking the seeds.

Also interested if there are any LED grow lights, or something that can be used for that. I only want them for the first few weeks seeds are raised in my shed, after that they go into my greenhouse. Everything on trademe/ebay seems expensive, even though LED strips and lights are typically really cheap. Heat mat is more important though, once they're up they can go into the greenhouse which gets decent light.

1 | 2

523 posts

Ultimate Geek
Inactive user

# 1390224 19-Sep-2015 13:44

I went down this road a few months ago and found the grow mats quiet inefficient over the winter months (in a cold shed). It was hard to maintain a constant temperature especially when some nights the temp in July/Aug drops to 5 Degrees (I live in Wellington).

I built a grow box instead which uses 2 X 25Watt Incandescent bulbs.
Buy yourself a black plastic storage box, put the bulbs in the lid, and line the inside and lid with some foil (or just use that cheap car front windscreen protection foil. Available from most dollar store).
Then I used a cheap digital thermometer and glued it to the outside of the lid (available on trademe). Stays at a constant temperature of +/- 23-25Degrees.

Box works really well. The nice thing is that it does not use that much electricity (50Watts). And it gets all my seedlings going in winter. Come spring and they go straight into the vegetable garden. The young plants also thrive inside the box (due to the light). You won't get the same effect from a grow mat, especially in winter.

timmmay

15389 posts

Uber Geek

Trusted

Subscriber

# 1390244 19-Sep-2015 14:29

That's an interesting way to do it :) Do the incandescent bulbs dry the soil out? Got any photos of your setup, or any tips? How did you connect the bulbs to the lid? Not sure I really want to do mains wiring myself.

DizzyD

523 posts

Ultimate Geek
Inactive user

# 1390273 19-Sep-2015 15:13

Yes they can dry the soil out. But I normally leave a piece of foil over the top of the seed tray until the seedlings start coming out.

I will get some photos for you.

I just bought two these for the light fittings. Then bolted directly into the lid, and wired in parallel. Not too much to it. But if you not comfortable in doing this kind of thing yourself then it may be best to try and find some fittings that are already all wired up. Otherwise ask an electrician to do it for you.

In my experience the box works really well. It can become very moist inside the box, a little subtropical micro-climate. Warm and humid. Ideal for growing seedlings. Most of my seedlings take only a few days to germinate when using the seed scarification method.

timmmay

15389 posts

Uber Geek

Trusted

Subscriber

# 1390297 19-Sep-2015 15:47

Interesting, thanks. I guess I could wire it up, I did do university level electronics, I just don't really like to mess with the mains if I don't need to. Sounds like a good way to do things :) I was going to head to the hardware store today, but might wait until tomorrow in case you come up with more insights or photos :)

Would you soak or scarify capsicum or jalapeno seeds? They're the only ones I'm having trouble getting to germinate right now.

DizzyD

523 posts

Ultimate Geek
Inactive user

# 1390363 19-Sep-2015 17:40

Here are some photos.

Top of lid with thermometer. Wire with probe (black wire) just goes through a whole in the lid into the box:
The brown wire is to the light bulb fitting. Bolts are what secures the light fitting to the lid.

The box (Bought this one from Bunnings.

Light fitting. Available from your local hardware store. Used a gluegun to stick on the foil.

Inside of the box. Foil cut to size and stuck on with gluegun.

Would you soak or scarify capsicum or jalapeno seeds? They're the only ones I'm having trouble getting to germinate right now.

I generally soak all seeds overnight. If they don't swell then I scarify.
capsicum seeds probably won't require scarification. Never done jalapeno. But that's sounds like something I should try out.

Good luck.

gumboot19

49 posts

Geek

# 1390409 19-Sep-2015 19:39

great idea's guys.
From memory, capsicums and chillies will not sprout under 18 deg/c soil temp.
I have some seeds trying to grow in punnets now, will put your advice to good use. In past years they have been too cold and waterlogged, so the seeds just rotted, not sprouted.
Red chillies are about $60 a kilo in Countdown at present. Most people I know just throw the ripe ones in the freezer, ready for winter stews etc.
Maybe one of those flat type homebrew heaters underneath would help? I suppose a plastic bag on top would let light in but not allow evaporation out?

Jase2985

8947 posts

Uber Geek

Lifetime subscriber

# 1390414 19-Sep-2015 19:51

never had any issues with them in my green house

timmmay

15389 posts

Uber Geek

Trusted

Subscriber

# 1390449 19-Sep-2015 21:28

Awesome, thanks for the photos :) They're not residential size bulbs right, they're smaller ones, any particular model? I can check bunnings or miter ten. Almost looks like a chilli bin sized box there.

Jase, you've raised capsicums and jalepenos in your greenhouse? I've started the seeds in just my $20 plastic mini greenhouse, but not until the weather's a lot warmer and my germination rate is awful - 10% maybe. I'm just trying to find a way to increase the odds without spending much money. It's just not worth spending much on this, given I can buy the plants for not much money, but I'd rather just sprout my seeds.

Jase2985

8947 posts

Uber Geek

Lifetime subscriber

# 1390480 19-Sep-2015 22:17

yep, last crop the plants were about 1.5m tall, the chillis had about 100 fruit on each, the jalapenos were about the same size with about 50 on each plant. capsicums, they were not too bad a little on the small side and im trying to find the variety the supermarkets use as the ones i have dont come out anything like theirs, still taste ok though.

i have a pretty good success rate with my seeds, well over 50% and i usually plant a heap more than i need, and just give them away to my friends and family. i just plant them in http://www.bunnings.co.nz/daltons-incredible-edibles-vegetable-mix-40l_p00343334 with a bit of http://www.bunnings.co.nz/daltons-organic-nufert-fertiliser-5kg_p00206401 in there and it seems to work sweet. Everything i grow i raise from seeds, except potatoes, which i just buy the seed potatoes.

Im about to start planting seeds once i recover the greenhouse (its a PVC tube, duratough PVC cover).

Jase2985

8947 posts

Uber Geek

Lifetime subscriber

# 1390482 19-Sep-2015 22:26

Picture of the plants mid season

i snapped a tendon in my knee in Jan so it pretty much all turned to custard and a bit went to waste as i wasnt there to tend to everything

throbb

611 posts

Ultimate Geek

# 1390488 19-Sep-2015 22:52

One person supports this post

I have raised a lot of chillies( Jalapeno, habanero, Scorpions, Ghost). I germinate all mine in the hot water cupboard in a good seed raising mix. This season I have had about a 90% success rate.

I also got a pretty decent/cheap grow lamp from aliexpress that I use for the seedling until the weather warms up a bit.

Coil

6615 posts

Uber Geek
Inactive user

# 1390493 19-Sep-2015 23:31

Thought you were going to go on about switched on gardening.

Interesting thing to do tho, I grew up on a horticulture block and we had plants and stuff. Usually just seeds in potting mix in the green house would work. But these were pre packed seeds.

timmmay

15389 posts

Uber Geek

Trusted

Subscriber

# 1390535 20-Sep-2015 09:21

My hot water cylinder is in my roof cavity. I do have a bathroom floor that's heated, I put the seeds in their little greenhouse in there at night, but during the day they're just on a window sill. Given the forecast is cloud and rain for the next two weeks I doubt they'll sprout there.

Heat mat sounds easiest, though the grow box with lights would help them get started pretty well. Mat is $50, grow box probably more like $100 by the time I find a good sturdy box, bulbs, connectors, insulation, plus a bunch of time to put it together.

Maybe I just keep poking seeds into dirt and hope for the best.

Niel

3267 posts

Uber Geek

Trusted

# 1390828 21-Sep-2015 00:08

Suggest you use car bulbs of similar total wattage and a transformer, or at least earth the foil and use an RCD. DIY mains wiring, foil, and water is an interesting combination.

You can easily add a temperature controller to regulate the temperature. You get digital DIN mount controllers with lots of programming options. Or an underfloor heating thermostat will also work well. But usually both of these options require mains wiring. Think I have a couple of hearing thermostats that I have no use for. (Timmmay, I'm not much on GZ any more so PM me if you want to contact me.)

You can never have enough Volvos!

timmmay

15389 posts

Uber Geek

Trusted

Subscriber

# 1390871 21-Sep-2015 07:45

I'm not sure I'm going to bother with a light box, just because it's too much hassle, even though it sounds very effective. I think the easy option of a premade heat mat inside a box sounds better. Sure it won't be as good once they've germinated, but it's easier and lower risk. I appreciate the offer and advice Niel :) Also appreciate the suggestion from DizzyD, sounds like a great plan just not for me.

1 | 2