How to germinate Carolina Reapers pepper seeds. When a organics meet electronics!


I will admit I suck at planting things. I wanted to grow Carolina reaper peppers and bought some seeds online, planted them and not much happened. Only one of five seeds germinated after about a month. So I did it the electronics way.

I used the Ziplock bag and wet paper towel method. It involves putting the seeds inside a moist paper towel then  put all of that into a ZipLock bag.
Allot of people will tell you its the best way. For me it wasn’t, I got to germinate one seed but it died after transplanting it from the paper towel to a small pot.
The problem with the ZipLock bag method is you have to intervene with the plant whilst it is still in it’s infant stage.

Also later after doing some research i found there there’s a general rule when it comes to peppers, “The hotter the pepper the longer  it takes to germinate” They are also know for not being beginner friendly. I thought of rather growing habanero peppers, but what’s the fun in that!.

After trying a few things over and over I found a very successful way to germinate them. Using this method  i got a 100% success rate so far. Even though they are known for taking up to month to germinate, I got them to sprout after only a week .

So what’s the big secret?
Constant temperature and a moist grow medium  is absolutely critical. Carolina reapers germinate at around 75F to 90F or 24C to 32C.

To create the perfect environment for the seeds I built a mini greenhouse with a thermal regulator. If the temperature goes above 29C it will turn off the heater and will turn back on again if it drops below 29C. For the grow medium i’m using peat which i bought from a plant store. I broke up the peat and then put it into a drinking cup.

Important note: In this post I’m showing you two different attempts. The first and the third. In the first attempt I used a Ferrero Rocher chocolate container which was a mistake. It worked fine but the seedling sprouted and with in 2 days grew too tall. I then built a wooden frame and covered it with see through fabric, but that was a total fail because the heater couldn’t bring the temperature up, it was too big. Then on my third attempt i used a smaller food container which i bought from a local plastics shop. Its big enough for the pepper to grow properly but small enough for the heater to evenly heat up the environment. Using the food container allows me to grow the pepper in this controlled environment until it has at least 4 or more leafs.

The first picture was the first attempt and the second my third attempt.


I mounted the electronics onto the back of the container with hot glue, The heater and temperature sensor is connected to the arduino with an eight strand cat 5 network cable. I drilled a hole at the bottom of the container routed it through the plastic using a rubber grommet to seal it.




The Parts

  • Container which is high enough so that there is enough space for it to grow strong.
  • Arduino UNO R3
  • Ni-chrome wire from an old fan heater, You can also find the same wire in an old toaster, hair dryer ect ect.
  • LM35 Temperature sensor
  • 5.00 V DC power source.
  • Some pre-drilled vero board.
  • LED, any single LED will do.
  • CAT5 Cable.

Using some old vero board to wind the nichrome wire to create a  small heating pad. After creating the heat pad I covered it using some fabric from the inside of an old laptop bag. I folded the fabric around the heat pad and then used to hot glue to keep it in place. In the below picture you will see 2 transistors. One is a LM7805 5v regulator and and IRL 520 negative mosfet transistor. The idea was to integrate the components into the heatpad but later decided to dump the 5V regulator and just use a 5V power supply and I mounted the IRL externally on a small bread board as show earlier on in this post.


The below sensor i bought from my local Arduino supplier. Its based on n LM35 sensor. It has 3 pins connecting to the Arduino Vin = 5v , GND and Vout which goes to A0 (Analog pin) on the Arduino.


The Results


This contraption is sitting on top of my printer close to my computer because the Arduino is powered via the USB and I’m also using custom developed software to monitor the temperature so that I can see how hot it is inside the container. There isnt  much light during the day in this area so I added a desk lamp with a CFL type lamp.


The software isnt included in this post, Its hardcoded to read COM Port7 which is the port my PC uses to communicate with the Arduino. If you are interested in the software I’m happy to make some changes so you can select the comport.

If you are going to also use a lamp for light make sure its a CFL lamp because they don’t become hot and wont melt the plastic or incinerate the poor plant.  I also closed it up with some foil partially because it’s heavy on the eyes and to try and concentrate all the energy onto the plant.


I’m using a 220V AC to 5V DC power supply in the below diagram.
This is how its connected, not shown in the below diagram is the LED. The LED goes to GND and Pin 7 on the arduino and will turn on and off along with the heater so tht you are able to visually see when the heater is on or off.


If you are already familiar with Arduino you will have no trouble grasping the below source code. Even if you understand a little bit about programming you should still get what it does.

The Arduino Code
//initializes/defines the output pin of the LM35 temperature sensor
int outputpin= 0;
//this sets the ground pin to LOW and the input voltage pin to high
void setup()
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
//pinMode(13, OUTPUT);
//main loop
void loop()

int rawvoltage= analogRead(outputpin);
float millivolts= (rawvoltage/1024.0) * 5000;
float celsius= millivolts/10;

     digitalWrite(8, LOW);
     digitalWrite(7, LOW);
     //digitalWrite(13, LOW);
     Serial.print(“Heater Off TEMP:”);
    digitalWrite(8, HIGH);
    digitalWrite(7, HIGH);
    //digitalWrite(13, HIGH);
    Serial.print(“Heater On TEMP:”);



Watch the video to have a closer look.

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