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Heated vs. Unheated Propagator - Which is Best?

Heated vs. Unheated Propagator - Which is Best?

Which is better at germinating seeds - a heated or unheated propagator?

We put 'em to the test! And here's what we found out.

What we Did

We bought 6 types of herb seeds:

  • Holy basil
  • Majoram
  • Oregano
  • Parsley
  • Sage
  • Purple basil

None had been crushed or cracked in transit - all seemed viable, so we got to work.

Step 1


VitaLink Plant Start and Canna Rhizotonic were mixed with some dechlorinated water.

The pH was adjusted to 6.5 and two trays of Grodan Cutting Seed Cubes were pre-soaked.

Step 2


As cubes were removed, excess moisture was squeezed out.

This made sure the rooting environment wasn't too moist. 

Step 3


Seeds were gently placed in the cubes. Where possible, they were covered with loose bits of rockwool

Step 4


We labelled trays as we went, so we know which plants came from which seeds.

By the time we were done, we had two identical seed trays. 

Step 5


One went into the Hi-Top Unheated Propagator.

The other went into a Hi-Top Heated Propagator.

Step 6


The propagators went into the same tent, each under their own T5 light.

Vents were left closed, to keep the humidity high.


We started seeing differences just 5 days in. 

Day 2

Already, small cracks were starting to form on seeds in the heated propagtor. There were still no signs of life in the unheated propagator.

Heated propagator - day 2


Unheated propagator - day 2


Day 5

There's been quite a bit of action in both propagators. 

Far more seeds had sprouted in the heated propagator. And they werere bigger - the purple basil especially!

It's worth noting that the heated propagator needed spraying with water at this point because the cubes had started to dry a little. This is something you need to keep an eye on if you use a heated propagator. 

Heated propagator - day 5


Unheated propagator - day 5


Day 7

By now, all seed varieties have sprouted in the heated propagator. They look pretty big, too.  

In the unheated propagator, the holy basil seeds are yet to germinate. 

Heated propagator - day 7


Unheated propagator - day 7


Day 9

By now, the seeds in the heated propagator are steaming ahead! They're much more advanced. More parsley seeds have germinanted in the unheated propagator but still no holy basil. 

Heated propagator - day 9


Unheated propagator - day 9


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About the author

Ian's our Sheffield shop manager. He loves tinkering in the greenhouse. Drop by to see what he's growing.

GroWell Hydroponics Sheffield

Call GroWell Sheffield:
0114 243 9242

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