Does the Slow Cooker Seed Hack Really Work? I Put It to the Test

My granddad always used to germinate his seeds in the crock pot. that lived under the counter and emerged each spring. Thanks to his slow cooker germination hack, it meant it was rarely filled with stew during the bleak midwinter, but with neatly labeled vegetable and flower seeds. I remember my nan getting cross when she’d go looking for it, only to find it already occupied by soon-to-be tomatoes or sweet peas.

At the time, it all felt very normal. Looking back, I wish I’d asked him more about it while I had the chance. Especially now his germination method has been having a major moment on social media, with plenty swearing by it as a cozy, low-tech way to start seeds.

It appeals to my instincts, as I love a thrifted solution; if something works without buying more gear, I’m all in. So, feeling nostalgic – and curious – I decided to put the slow cooker method to the test myself. Could this old-school trick really replace a heat mat? And more importantly, is it worth the effort for modern gardeners?

How the Slow Cooker Seed Hack is Supposed to Work

On paper, the method is simple. The idea is to use a slow cooker to create a warm, humid environment that mimics ideal soil temperatures for germinating seeds.

Most versions of the hack go something like this:

• Add 1-2 inches of water to the bottom of the slow cooker
• Place a metal trivet or rack inside so seeds sit above the water
• Put seeds in a plastic bag or container with a damp paper towel (or cloth, if you want to be extra sustainable)
• Set the slow cooker to its lowest setting (usually “Warm” or “Low”)

The target temperature is typically around 75-85°F (24-29°C), though this varies by plant. Some seeds love warmth; others really don’t. Get it wrong, and you risk either stalling germination or... well, or cooking your seeds outright. Oops.

When Modern Appliances Get Too Clever

My own slow cooker is gloriously basic, with just three settings: Low, Warm, and Hot. But for my first attempt, I commandeered my father-in-law’s kitchen and tried using his Ninja multi-cooker instead. This was a mistake.

Somewhere between overconfidence and button-happy curiosity, I accidentally set it to air fry. The tomato seeds never stood a chance. It was a complete failure, and a good reminder that many modern appliances run hotter than we think, even on their lowest settings.

Chastened, I returned home and dusted off my old faithful slow cooker, determined to keep things simple.

This time, I did what I’d strongly recommend to anyone trying this hack: I checked the temperature with a cooking thermometer. Even on the lowest setting, the internal temperature hovered around 104°F (40°C), which is far hotter than most seeds want.

I removed the lid to let some heat escape and managed to bring it down to just over 86°F (30°C). Still on the warm side, but closer to the acceptable range. In went my mini cucumber seeds, which prefer higher germination temperatures than many other crops.

Then I waited, but after almost 76 hours, there was still no sign of life. At the time of writing this article, the seeds could be right on the brink of germinating, or they could be quietly giving up the ghost. With temperatures fluctuating and constant monitoring required, it's hard to know for sure.

So... Does the Slow Cooker Seed Hack Work?

Here’s the thing: I know that the slow cooker seed hack can work. Plenty of gardeners have had success with this method. As I say, my granddad swore by it for years, so I guess maybe older crock pots ran cooler and more steadily than many modern ones.

But still; “can work” and “is worth it” aren’t quite the same thing.

Using a slow cooker for seed germination requires careful temperature monitoring, frequent adjustments, and a willingness to sacrifice your slow cooker for days at a time. During soup and stew season, that’s a big ask. And if your appliance runs hot, as many do, the margin for error is small.

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For me, the slow cooker hack feels like a lot of effort for limited payoff. Yes, it can save you money upfront. But it also introduces stress, uncertainty, and the very real possibility of cooking your seeds before they ever sprout.

Reluctantly, and I mean reluctantly, I’m firmly in the heat mat plus thermostat camp. And that’s coming from someone who hates buying new things. I only just retired a pair of 10-year-old jeans after they survived countless dog walks, gardening sessions, and two pregnancies.

A basic heat mat setup gives you consistent, seed-appropriate warmth without the guesswork. It lasts for years if you look after it, frees up your kitchen, and removes the fear of ruining both your seedlings and dinner plans.

My granddad wasn’t wrong: he worked with what he had, and it served him well. But gardening evolves, just like our tools do. And sometimes, the best solution is the one that lets your seeds germinate safely… without putting soup season at risk.