What's All This About Hügelkultur?

How to Start a Hügelkultur Garden

If you're planning to start a garden in hard-packed clay or depleted soil, the Hügelkultur method might be for you. OR if you're building a raised bed this method can help you cut the cost of soil significantly in your first year.

Hügelkultur translates to "hill culture" or "mound culture." This technique helps gardeners mimic natural processes to build rich, fertile soil. Think about walking in a forest, where the ground is thick with layers of decomposing leaves or pine needles—you can feel you’re inches above the actual soil line. When you move this mat aside, you find rich, moist soil beneath. If you dig further, you might find segments of old branches, slowly breaking down over time. Hügelkultur replicates this process, cultivating healthy soil in your own garden.

In one example, this method was used in a school garden with no initial budget. With the support of friends in landscaping and a lot of hope for a productive garden, we set up the beds. By the end of the first season, we harvested between 250-300 lbs of tomatoes right before the first frost (mostly green in October, haha). We didn't weigh or track earlier harvests, but fresh tomatoes, basil, and other garden goodies were plentiful throughout late summer.

For raised beds that are 3.5 feet or taller, filling the lower part of the bed with layers of the following materials as described can save you the cost of fully filling it in with soil and compost initially. 

Benefits of Hügelkultur for Any Region

Hügelkultur offers a range of benefits to gardeners in diverse climates and soil types:

• Soil Fertility and Nutrient Retention
  The gradual decomposition of materials like branches, grass clippings (untreated of course), leaves, and manure enriches the soil with nutrients over several years, making it especially helpful for gardens in nutrient-poor or hard-packed soils.

• Moisture Retention
  The organic matter in a Hügelkultur mound holds water like a sponge, which can be a lifesaver in dry regions. The mound’s structure helps store moisture in the soil, reducing the need for frequent watering, even in the heat of summer.

• Temperature Regulation
  Decomposition generates heat, which can help extend the growing season in colder climates. The warmth produced can prevent the soil from freezing as quickly, allowing gardeners to harvest later in the season.

• Enhanced Soil Structure
  In clay soils, Hügelkultur improves aeration and soil structure, making it easier for roots to grow. The layered organic materials break down over time, loosening heavy soils and creating a more friable, loamy consistency.

• Biodiversity Boost
  By adding mushroom blocks or “spent mushroom substrate,” you introduce beneficial mycelium and microbes to the soil, promoting healthy, biodiverse ecosystems in your garden.

Things to Prepare For

Hügelkultur rows will settle significantly over time, often by a foot or more each season, as the organic material decomposes. Here’s how you can maintain and build up your rows each year:

• Annual Layering
  Each fall, add a fresh layer of decomposing organic materials like leaves, manure, mushroom substrate, and straw. If you grow broomcorn, include its stalks and leaves as they’re rich in nutrients similar to those in sorghum. These materials break down over 1-2 years, further enriching your soil.

• Top with Compost or Soil
  Add 2–4 inches of compost, which can often be acquired for free through city programs (available in Boise; check with your local city or town for similar resources). If free compost isn’t available, use soil from other garden expansion projects, mixing it with aged manure or compost to ensure nutrients.

• Finish with Leaves and Straw
  Cover the compost or soil layer with another round of leaves, then top with straw to keep everything in place. The straw helps to prevent leaves from blowing away, maintains soil moisture, and can even help deter or suppress weeds. Regularly adding these layers keeps your Hügelkultur beds productive and reduces the need for chemical fertilizers or intensive watering.

Building a Hügelkultur Mound or Row: The Basic Layers

To create a Hügelkultur bed, layer organic materials to form a mound or row, starting with larger, slower-decomposing items at the bottom and working up to finer, quicker-decomposing materials at the top. Here’s a suggested order of layers to achieve the best results.

If you're gardening in heavy clay or depleted soil and have a minimal budget, you can start by digging a trench that's about 2.5 ft wide x 1 ft deep, however long you want it to be. Save the top 6 inches of soil in one pile, and save the rest in a separate pile.

1. Decomposing Leaves and Large Branches

   • Start with a base of decomposing leaves and large branches.
     
     

2. Manure

   • Add a generous layer of manure. This will help balance the nitrogen that wood materials might deplete as they decompose.
     
     

3. Leaves

   • Use mostly oak and maple leaves if possible.
   • Avoid leaves from black walnut or hickories, as they can inhibit plant growth.
     
     

4. Smaller Branches

   • Stack smaller branches on top of the larger ones.
   • Avoid using black walnut, locust, bamboo, or invasive vines like Virginia creeper.
     
     

5. Wood Chips

   • Add wood chips, but balance this layer with plenty of manure to compensate for nitrogen depletion during decomposition.
     
     

6. Aged Manure

7. Small Branches, Leaves, and Grass Clippings

   • Add a final layer of smaller branches, leaves, and grass clippings (make sure they aren’t seedy).
   • Stuff these between the upper branches for added structure and organic matter.
     
     

8. Sod Clumps with Soil

   • Break up sod clumps with soil to introduce more earth and microbial life into the mound.
     
     

9. Grass Clippings and Leaves

10. Mushroom Blocks (Optional)

    • If possible, add 4–6 mushroom blocks (spent mushroom substrate or "spawn"). These introduce mycelium, increasing soil biodiversity.
      Pro tip: Local farmers' markets may have mushroom growers who sell spent substrate. Expect to pay around $100 for a delivered load in Boise. Support the farmer!
      
      

11. Compress and Soak

    • Walk carefully over the pile to compress the layers.
    • Then, soak it thoroughly with a hose to start the decomposition process.
      
      

12. Soil, Manure and Mushroom Substrate (if you've got em) Layer

    • Mix and Apply: Combine equal parts of soil and manure with a few mushroom blocks, then spread this mixture evenly over the mound. This layer will help hold down the branches and add essential nutrients.
      • Use as much manure as needed for a rich mix.
    • Add Soil Layer: If possible, cover with 4–12 inches of soil on top. This helps seal in moisture and protect the decomposing materials below.
      • 12 inches is an ideal starting depth for root crops.
      • If you don't have that much soil left from your initial digging to build the row, you may need to supplement with additional soil from your local nursery or garden center.
      • Frugal method: You can also use pots with the bottom cut out to hold that space, packed with a bag of organic potting soil.
        
        

13. Wet and Secure

    • Lightly wet down this top layer with a gentle spray (you can fan the water by using your thumb over the hose). Be careful not to wash away your soil—just get it wet and muddy.
      
      

14. Final Mulch Layer

    • Add leaves and then straw on top to hold in moisture and add further microbial life to your soil.
    • Spray lightly to secure it in place.

Seasonal Maintenance

• Fall: Add a layer of manure from an older pile to insulate and enrich the bed.
• Spring: If you didn’t add manure in the fall, use a light layer of aged manure or compost instead. Let the bed rest for at least a month before planting, allowing the manure to integrate and avoid overwhelming your seeds or seedlings.

To finish, add a light covering of straw to hold everything together, then spray it one last time to settle the materials. Your Hügelkultur bed is now set up for planting next season!