Ditch the seed heat mats and build your own low-cost DIY germination chamber to jumpstart your vegetable garden this year. This low-cost alternative requires no tools or special handyman skills to set up and can fit more flats than a single heat mat. A homemade germination chamber will set you up for seed starting success with all your favorite heat-loving summer vegetables.
Why heat matters
If you’ve struggled to grow tomatoes, peppers, and eggplants from seed year after year and wondered why those seeds never even sprouted, it’s likely the temperature was too cool in your seed-starting area. The temperature needed for tomatoes, peppers, and eggplant to germinate successfully is typically a lot warmer than our basements, garages and windowsills in February when we need to get our seeds started! Here’s the ideal temperature break down for optimal seed germination:
- Tomatoes – 70-80F
- Peppers – 75-85F
- Eggplants – 75-85F
Toasty, right? Even here in South Carolina our basement holds closer to 60 degrees in the winter. Not quite going to produce the best seed germination results for these heat-loving crops. Last year it took about 3 weeks for peppers to germinate and over 4 weeks for eggplants. With only one seed-starting heat mat to go around, germination was very poor for the homestead garden. Enter this nifty and affordable DIY germination chamber.
What is a Germination Chamber?
A seed germination chamber is an enclosed space where the temperature and humidity can be controlled for optimal seed germination. A 6-shelf model starts at over $4000! Yikes! Large-scale farms and seedling nurseries might be able to afford a fancy option like that, but definitely not small farms and homesteads. Thankfully there’s a simple way to recreate the perfect growing environment for a fraction of the cost.
DIY Germination Chamber Supplies
- Incandescent light bulb (25-50W)
- Reptile thermostat
- Large Cooler – can be used or broken (one of ours was found in someone’s trash pile!)
- Heat Clamp Lamp with reflector
DIY Germination Chamber Set-Up
Step 1 – Locate your cooler
You will need a cooler large enough to fit your seed starting flats and lids. This can be the cooler you take to the lake and beach in the summer, no need to buy anything new! One of our large coolers was found in someone’s trash pile and another one on Facebook Marketplace for cheap. It can even be broken. Nothing fancy required, just needs to fit your flats and humidity dome lids.
Step 2 – Order your supplies
Assuming you already have a cooler on hand, you’ll probably need to order or shop for the other supplies. The reptile thermostat and heat clamp lamp are easily found online at Amazon at an affordable price. If your house has converted to LED, you’ll also need to source an incandescent light bulb in the 25W-50W range. (If you’re having trouble finding one in the US, search for an oven light bulb as many of those are still incandescent.)
Step 3 – Assemble your germination chamber
Screw in your light bulb into your clamp lamp and set it inside the cooler along with the temperature probe for the reptile thermostat. Plug your thermostat in and set it to the optimal temperature range for your seeds. Place your watered/moist seedling trays or flats with their humidity domes directly into the cooler. (We have been able to stack 4 high without cracking our plastic domes.) Then close the cooler and let the thermostat do its job!
Step 4 – Remove after germination
Per usual, you’ll want to remove the humidity domes as soon as your flat of seeds has germinated to prevent damping off. So check in on your flats every few days to mist with some water and see if they have germinated yet. Once they have, remove them from the germination chamber, remove the humidity dome, and set under light.
Happy seed starting! For more seed-starting content check out these blog posts.