The Ultimate Guide to Aerobic Composting for Thriving Flower Gardens

I never thought I would get excited about talking compost. But after seeing the dramatic difference a good aerobic compost can make in flower farming, I’m hooked. The quality, quantity, and vase life of flowers grown with rich, well-made compost far surpass anything I expected. If you love flowers, understanding how to make aerobic compost will open up a whole new world of gardening success.

Understanding Hot and Cold Compost

Before diving into how we make compost on the farm, it helps to know the difference between hot and cold compost. Cold composting is a slower process where organic materials break down naturally over many months or even years. It requires less effort but also produces compost more slowly and doesn't kill weed seeds or pathogens.

Hot composting, on the other hand, is an intense, fast process that heats the pile to temperatures between 55 and 65 degrees Celsius. This heat kills weed seeds and pathogens while speeding up decomposition. Hot composting produces rich, ready-to-use compost in just a few weeks. It takes more work but the results are worth it, especially for flower farming where soil health and nutrient availability are critical.

Our 18-Day Hot Compost Method

On our farm, we use an 18-day hot compost method. It’s intense but the payoff is huge. Here’s how we do it:

• Brown material (about 30%): We use wood chips from pruning and tree trimmings. This provides carbon and structure.

• Green material (about 60%): Old plants from the garden, fresh leaves, and vegetable scraps. This adds nitrogen and moisture.

• High nitrogen material (about 10%): Grass clippings are our go-to here. They boost nitrogen levels to fuel microbial activity. High nitrogen materials function like the accelerator in a car. Raising their percentage helps speed up the pile to reach the desired temperature. Decreasing the amount of high nitrogen materials will slow the process.

• Extras: We sprinkle in paramagnetic rock dust from a local quarry to add trace minerals that support plant growth.

• Starter compost: A handful of good quality compost we’ve already made helps jump-start the microbial community.

  
  

We layer these ingredients using a lasagne method, building the pile in approximately 5cm layers. After each layer, we sprinkle water to keep the moisture level right. The pile grows until it reaches between 1 and 3 cubic meters, standing at least 1.5 meters high.

Managing Temperature and Turning the Pile

Temperature is the key to successful hot composting, so a good quality compost thermometer is a must-have. When the pile reaches 60 degrees Celsius, it’s time to turn it. Turning aerates the pile, mixes materials, and prevents overheating. You don’t want the temperature to go above 70 degrees because that can kill beneficial microbes essential for compost quality.

We turn the pile every time it hits 60 degrees or higher. This will happen several times over the 18 days until the pile cools down naturally. The turning process is hard work but critical for producing compost that will boost flower growth and soil health.

Once the compost pile reaches a stable temperature after turning (usually after 18 days or so), it’s good to go! The compost can be applied to garden beds in a 5-10 cm layer and planted into directly. It's not necessary to "dig in" the compost, contrary to what many sources suggest.

Adapting Composting to Your Environment

Every garden and farm is different. Weather, climate, and available materials will affect how your compost behaves. You’ll need to tweak the method to fit your situation. The best way to learn is to jump in and try it. Expect to fail a few times at first — that’s part of the process. Each attempt will teach you something new.

Here are some general rules to keep in mind:

Turn the compost whenever it reaches 60°C or higher.

If the compost smells bad, slimy, or sour when you turn it, something isn’t right. This usually means the pile is too wet or hasn’t been turned often enough. Turn it more frequently to correct the issue.

If the pile doesn’t reach 60°C within the first day or two, it may lack water or green (high-nitrogen) material. Use the squeeze test: grab a handful of compost and squeeze it—a few drops of water should come out, but it shouldn’t drip.

• Add water if it’s too dry.

• If moisture is fine, add more high-nitrogen materials.

If your pile reaches 70°C or higher, don’t worry. This just means you should turn it more regularly or reduce the amount of high-nitrogen materials.

Why Aerobic Compost Matters for Flower Farming

Aerobic composting supports the no dig approach we (and our plants!) love. Instead of disturbing soil structure by digging, you build soil health naturally with compost. This encourages beneficial microbes and earthworms, improves soil texture, and provides steady nutrients for flowers.

The result? Flowers that bloom more abundantly, have richer colors, and last longer in the vase. For flower lovers, that means more joy from every bouquet and a garden that thrives year after year.