Here is a truth that most new gardeners overlook: the best thing you can plant in an empty garden bed is not a vegetable. It is a cover crop.
While your main crops rest between seasons, bare soil is losing nutrients, eroding, compacting, and growing weeds. Cover crops fix all of that, and they do it cheaply and naturally. If you want to build genuinely incredible soil over time, this is the technique that will get you there.
What Are Cover Crops and Green Manures?
The terms are often used interchangeably, but there is a subtle difference:
- Cover crops are planted primarily to protect and improve the soil. They cover bare ground, prevent erosion, and suppress weeds.
- Green manures are cover crops that are specifically chopped and incorporated into the soil to add organic matter and nutrients.
In practice, most cover crops serve both purposes. You grow them, chop them, and work them into the soil (or leave them on the surface in a no-dig system) to feed the next crop.
Why Bother?
The benefits are significant:
- Prevent erosion. Living roots hold soil in place. This matters enormously in heavy rain or windy conditions.
- Suppress weeds. A dense cover crop outcompetes weeds, reducing your workload in the next season.
- Fix nitrogen. Legume cover crops (peas, beans, clover) form partnerships with soil bacteria that convert atmospheric nitrogen into plant-available nitrogen. Free fertiliser.
- Add organic matter. When you chop and incorporate a cover crop, all that plant material breaks down into humus, improving soil structure, water-holding capacity, and microbial life.
- Break pest and disease cycles. Rotating cover crops through your beds disrupts the life cycles of soil-borne pests and diseases.
- Feed soil biology. Living roots feed the microbial community in your soil all year round, keeping the underground ecosystem thriving.
The Best Cover Crops for Australian Gardens
Here are the most useful and readily available options for home gardeners across Australia.
Cool Season (Autumn/Winter)
| Cover Crop | Type | Key Benefit | Sow |
|---|---|---|---|
| Broad beans | Legume | Nitrogen fixer, lots of biomass | March to May |
| Field peas | Legume | Nitrogen fixer, quick growing | March to June |
| Crimson clover | Legume | Nitrogen fixer, beautiful flowers | March to May |
| Oats | Grass | Weed suppressor, lots of biomass | March to June |
| Lupins | Legume | Deep roots, nitrogen fixer | March to May |
Warm Season (Spring/Summer)
| Cover Crop | Type | Key Benefit | Sow |
|---|---|---|---|
| Mung beans | Legume | Nitrogen fixer, fast growing | October to January |
| Cowpeas | Legume | Heat tolerant, nitrogen fixer | October to January |
| Buckwheat | Broadleaf | Fast ground cover, pollinator food | September to February |
| Mustard | Brassica | Biofumigant, fast growing | September to November |
| Japanese millet | Grass | Masses of biomass | October to January |
PLAN YOUR SOIL BUILDING STRATEGY
Schedule cover crops into your garden rotation
VeggieCrush helps you plan what to grow between your main crops, so your soil keeps improving season after season.
Download the free appHow to Grow Cover Crops
Step 1: Choose Your Crop
Match your cover crop to the season and your goals. Want to fix nitrogen? Choose a legume. Want to suppress stubborn weeds? Go with a dense, fast-growing grass like oats. Want both? Mix a legume with a grass (broad beans and oats is a classic combination).
Step 2: Prepare and Sow
- Clear the bed of any old crop residue.
- Lightly loosen the top few centimetres of soil (or just scatter seed on top in a no-dig system).
- Broadcast seeds densely. Cover crops work best when sown thickly, so do not be stingy.
- Rake lightly to cover seeds, or top with a thin layer of mulch.
- Water in well.
Step 3: Let It Grow
Cover crops need minimal care. Water them if it is dry, but mostly they just get on with it. Let them grow until they are flowering but before they set seed. This is when their nutrient content is highest and the biomass is at its peak.
Step 4: Chop and Incorporate
You have two main approaches:
Traditional method: Cut the cover crop at ground level, roughly chop the material, and dig it into the top 10 to 15 cm of soil. Wait two to four weeks before planting your next crop, as the decomposing material can temporarily tie up nitrogen.
No-dig method: Cut the cover crop at ground level and leave the material on the surface as mulch. The roots decompose in place, creating channels for air and water. Add a layer of compost on top and plant directly into it. This is gentler on soil biology and works beautifully.
Planning Cover Crops Into Your Rotation
The trick is to think of cover crops as a regular part of your garden calendar, not an afterthought. Here is a simple approach:
- After summer crops come out (March to April): Sow a cool-season cover crop like broad beans and oats.
- Chop in early spring (August to September): This gives the material time to break down before planting warm-season crops.
- After winter crops come out (October to November): Sow a warm-season cover crop like buckwheat or cowpeas.
- Chop in late summer (February to March): Ready for your autumn veggie planting.
Even if you only cover crop half your beds each year on a rotation, the soil improvement is dramatic over just a few seasons.
BUILD BETTER SOIL YEAR AFTER YEAR
Track your soil improvement journey
VeggieCrush helps you plan crop rotations including cover crops, so you always know what is growing where and what comes next.
Download the free appCover Crops and No-Dig Gardening
If you follow a no-dig approach (and we are big fans), cover crops fit in perfectly. Instead of digging the material in, you simply:
- Chop the cover crop at ground level.
- Leave the roots in the soil to decompose naturally.
- Lay the chopped material on the surface.
- Top with a layer of compost.
- Plant your next crop directly into the compost.
The decomposing roots create incredible soil structure over time, with channels that improve drainage and aeration. The surface mulch feeds the soil from above while the roots feed it from below. It is soil building at its finest.
Cost-Effective Soil Improvement
Cover crop seeds are cheap, especially when you buy them in bulk from agricultural suppliers rather than garden centres. A kilogram of broad bean or oat seed costs very little and will cover a large area.
Compare that to buying bags of commercial soil improver or fertiliser, and cover cropping comes out miles ahead. You are essentially growing your own fertiliser and soil conditioner for the cost of a packet of seeds.
The Bottom Line
Cover crops are one of the most powerful tools in a gardener’s toolkit, yet most home gardeners never use them. They build soil, suppress weeds, fix nitrogen, prevent erosion, and feed the underground ecosystem that makes everything else in your garden thrive.
Start simple. Next time a bed empties out between seasons, scatter some broad bean or oat seeds and let nature do the rest. Your soil will be better for it, and everything you plant afterwards will grow more vigorously as a result.
Your future self (and your future veggies) will thank you.
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