Sterilising soil saves gardening heartache

Even when I look at the picture, I can smell it.

The olfactory memory kicks in and I fill the sterilizer, set the timer, and pop in the thermometer. The unique smell of boiling compost/soil.

The winter wind is blowing and my face is numb from the cold. Still only 80 minutes until the chef is done.

Steamy heat

After the tea break, come back and lift off the heavy lid. A touch of steaming heat and the unforgettable smell hit body and soul.

My face is temporarily soothed by the lovely warmth. Like clothes straight out of the tumble dryer.

But I’m not just looking at a picture of it now. It’s already time again.

Unsterilized compost in the bay.

sterilize soil

We sterilize our compost over the winter. Accumulated compost from previous years is stored in a bay outside in the work yard.

All garden waste to unwanted items go here. Undesirable items include debris, litter, clippings infected with pests or diseases, or harmful weeds.

We transport the compost from outside and fill up a large bay inside the workshop. Unsterilized compost used in bedding soil mixes can be full of weed seeds.

Consequently, you have unfavorable competition with your newly sprouted seed trays.

The sterilizer is fully loaded.

In addition, there is a greater risk of attracting pests and diseases such as fungus gnats and curbing disease.

Not to mention the time and effort required to weed the pods around the germinating seeds. It can also contain invisible bacteria or fungi that can harbor disease.

While it may seem like a farce, it’s a short-term investment to avoid long-term pain. Let’s be honest, at home you probably buy a bag of compost from the garden center.

Large gardens

This will mostly be clean stuff and you don’t need to sterilize it. As the team and I work in large gardens that make their own compost it is required for us.

However, if you make your own compost at home and make your seed mixes, do you sterilize? It’s all up to you!

Feel free to risk it and just make your mixes without sterilization. When the weed seeds appear, you probably have time to weed them.

Imagine you have thousands of trays to take care of. It changes a bit, doesn’t it?

The timer is set and cooking is in progress.

do it at home

While there is certainly less of a need at home, it is very possible to sterilize at home if you feel like it.

You can simply place your soil in an ovenproof dish, then cover with foil and turn the oven on low (130 degrees Celsius) for about 30 minutes. Make sure the soil contains some moisture or doesn’t steam well.

The right consistency is when you can grab a handful and it holds its shape but still breaks apart easily. The soil can be used once it has cooled.

topping up

We create about three cooked batches of soil per day. A batch is a wheelbarrow full (85L).

Every morning we load the sterilizer with sifted compost. By shaking we remove any waste or odd pieces of compost that have not been properly shredded.

When it’s a bit dry we give it a spritz with a watering can to moisten it. After all, it is the steam that sterilizes. No moisture, no sterilizing. The timer is set and we let it cook.

Sterilized compost on the left, unsterilized on the right.

Once it is ready, we lift the lid and pull the slats under the sterilizer so that it falls into the wheelbarrow waiting underneath.

The wheelbarrow is emptied into a separate bay in the shed. Sometime during the winter; Cartload by cartload we fill up a bay with clean soil.

Essentially, initially one bay is full of non-sterile compost while the adjacent one is empty.

In the end, the empty one is filled with sterilized compost, while the previously full one is empty.

Draw from it all the parallels to the smart life that you want. This cove of clean soil has eradicated weed seeds and any culprits during cooking and forms part of our summer bedding soil mixes.

life cycle

i love the smell It’s literally the smell of the past, present and future. Past: Compost from past plants. Present: Compost Cooking! Future: summer bedding to be.

If you only sow a few bowls at home, this may not be necessary. However, at the scale we sow (more than 20,000 annuals each year between February and April) we need to minimize the damage. It is part of the garden’s annual cycle.

Part of the ebb and flow of a wonderful historic horticultural site.

All the best and happy gardening.

Already a subscriber? log in

[Sterilising soil saves gardening heartache]

[[text]]

Close