Introduction: Understanding Green Manure and Spring Cover Crops
Knowing what to do with cover crop in spring is key to maintaining healthy, fertile soil. As temperatures rise, your spring cover crops—whether planted last fall or early spring—begin rapid growth. The next step is to turn them into green manure, an organic way to boost soil health and fertility.
Green manure refers to cover crops like winter rye, annual ryegrass, and leguminous species such as hairy vetch that are grown specifically to be cut down and returned to the soil. These cover crops and green manures naturally improve soil structure, retain moisture, suppress weeds, and fix nitrogen—all without synthetic inputs.
To see the process in action, check out our Green Manure How-To Video.
For a broader overview of cover crop benefits, species, and seasonal timing, read our Introduction to Cover Crops – A Growing Guide and browse our full Cover Crops Collection.
Benefits of Green Manure in Spring Gardening
Incorporating green manure into your gardening routine has long-term benefits for soil health and productivity. Whether you garden till or follow a no tilling gardening approach, turning spring cover crops into green manure enhances your soil in the following ways:
- Improves soil fertility by adding organic matter and fixing nitrogen (especially with legumes)
- Prevents erosion by shielding the soil from wind and rain
- Suppresses weeds by blocking light and competing for nutrients
- Increases water retention by improving soil structure
- Encourages beneficial microbes and insects
If you’re exploring how to use cover crops in a no till garden, green manures can be a foundational strategy. For summer applications, check out The Essential Guide to Summer Cover Crops and our blog on Growing Cover Crops in Summer.
You can also shop for specific soil-building varieties in our Green Manure Seeds Collection.
When to Cut Cover Crop
Timing matters. Knowing when to cut cover crop ensures you're getting the most out of its biomass and nutrient value.
- Cut before the crop goes to seed. If it sets seed, you risk weed problems later.
- The ideal time is when about 50% of the crop is flowering—this is peak biomass.
- Wait 3–6 weeks after cutting before planting your next crop. This allows decomposition and prevents temporary nitrogen lock-up.
Need inspiration? Our full Cover Crops Blog is packed with tips and timing guides for different zones and plant types.
Techniques for Turning Cover Crops into Green Manure
1. Tilling Cover Crops
The most straightforward method is to till the cover crop into the soil. This breaks it down rapidly, turning the organic matter into nutrients for your next crop.
- Pros: Fast decomposition, less nitrogen lost to the atmosphere.
- Cons: Disturbs soil structure; doesn’t provide weed suppression or mulch while decomposing.
Use a rototiller or disc harrow for large areas. Read more about this process in our guide on Tilling Cover Crops.
2. Mow and Mulch (No-Till Gardening Method)
In no till gardens, mow or cut the crop and leave the residue on the soil surface as mulch.
- Pros: Conserves moisture, suppresses weeds, supports soil organisms.
- Cons: Slower decomposition, may not kill some cover crops completely.
To get started with no tilling gardening, visit our full No-Till Gardening Guide.
3. Cut and Compost
Cut your cover crop with a hand sickle, weed-eater, or scythe, compost it, and return it to the soil.
- Pros: Produces nutrient-rich compost over time; ideal for raised beds.
- Cons: More labor-intensive and takes longer (several months).
Pair this with our Bark Mulch (2 cu ft) for extra moisture retention and weed control.
4. Rolling or Crimping
Use a roller or your tiller (with tines off) to flatten cover crops.
- Pros: Minimal soil disturbance; useful in no-till systems.
- Cons: May not fully terminate the crop, especially aggressive species.
Tools and Equipment for Cover Crop Management
Whether you’re cutting, mowing, or tilling, using the right tools can make your job easier and more effective.
Recommended Tools
For Large Plots or Fields:
- Flail mowers – Great for chopping large biomass into fine mulch that decomposes quickly.
- Rotary mowers – Effective for managing thick or tall cover crops like rye and vetch.
- Disc harrows and rototillers – Ideal for incorporating biomass in garden till systems.
For Small Gardens or Raised Beds:
- Hand sickles and scythes – Traditional tools that give precise control in small spaces.
- Weed eaters – Fast and accessible option for mowing cover crops in home gardens.
- Compost forks and garden carts – Helpful for managing composted cover crops.
Browse our Tools & Equipment Collection to find exactly what you need for your space and scale.
Safety & Maintenance Tips
Managing equipment responsibly ensures both your safety and the longevity of your tools:
- Wear PPE: Use gloves, goggles, ear protection, and closed-toe shoes when operating powered tools.
- Pre-check your tools: Inspect for loose bolts, dull blades, or frayed belts before each use.
- Clean after use: Remove dirt and plant residue, especially from tiller tines and mower decks.
- Lubricate regularly: Follow manufacturer guidelines for oiling blades and bearings.
- Store tools properly: Keep them in a dry, sheltered place to avoid rust or weather damage.
Following these best practices will keep your tools performing well throughout the seasons.
Conclusion
By turning spring cover crops into green manure, you build rich, resilient soil for the growing season ahead. Whether you’re tilling cover crops into the ground or exploring how to use cover crops in a no till garden, the results are the same: enhanced fertility, improved soil structure, and fewer weeds.
Explore related resources and products:
Your soil—and your future harvests—will thank you.
Grow Organic. Grow Smart.
FAQs: Green Manure and Spring Cover Crops
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What to do with cover crop in spring?
- You should cut it down before it goes to seed, then either till it into the soil, mulch it in place, or compost it—depending on your gardening system and timing.
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When to cut cover crop?
- Cut it when about 50% of the crop is flowering to get the most biomass and nutrient value. Avoid letting it set seed.
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Can I use cover crops in a no till garden?
- Absolutely. Mow or roll the cover crop, leave it as mulch, and let it decompose naturally.
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How long should I wait to plant after turning under a cover crop?
- Wait about 3 to 6 weeks. This allows the green manure to decompose and prevents nitrogen tie-up.
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What’s the difference between tilling and no-till methods for cover crops?
- Tilling incorporates the crop quickly for faster decomposition, while no-till methods preserve soil structure and moisture but take longer to break down.
22 comments
Elle, sent your question to our garden advisor, Janice, and this is what she says, “Unknown if any research on success of cover crop to thwart this type of oxalis exists. It thrives on disturbed soils so preparation for cover crop introduction would be counter-indicated. However, a dense stand of a grass that stabilizes the soil would probably hinder spread. Maybe introduce as plugs well rooted so they can establish – obviously a long term project.
Sheet mulching is effective if repeated and wide enough to deal with perimeter issues. Work is being done with tilling in the fall/winter when oxalis emerges and before it flowers and then repeating 2 weeks later. Thought is that bringing root and growth material to surface with degrade.”
I have oxalis growing on a steep slope in my SF east bay backyard—the hill is covered. I’ve tried digging them out to no avail. I tried solarizing with plastic, but it didn’t work either, the bulbs are too deep. I thought maybe a strong weed suppressing ground cover might help. The ground cover would need to work in the fall and winter as Oxalis pes-caprae (yellow buttercup strain) is from South Africa and grows during our rainy season. I remembered reading somewhere that higher nitrogen might retard it, so was thinking a nitrogen fixing ground cover that forms a strong weed suppression mat might help. Any suggestions? The other issue is planting since on a fairly steep hill with dirt over serpentine rock, so would have do seeding by hand. I’d appreciate any suggestions.
Don’t till. Just chop and drop. Any plant material left will eventually decompose and become mulch if you want to plant something before it’s all dry and crumbly, just scooch the greenwaste to the side and plant…no till is the way to go. Tilling destroys soil structure and causes erosion and lack of tilth
Early spring planting is my favorite for peas as cover. Sometimes I mix a 1:1 ratio of cut biomass to finished compost so I don’t burn anything. Laying it on top works for light fertilizing, weed control, and water retention for a raised bed. The big garden gets tilled in early spring when the pea plants are young. A lawnmower and tiller is fine for this. Just cut and turnover. Hope this helps
Helen, the large clumps are a bother. You can know out as much soil out of them and put them in your compost or just turn them under. You could also put some weed fabric over it and let it just die out and it should break down over 2-3 weeks.