You may have heard about green manure before but are still unsure as to what exactly green manure is, well let me help you out with this complete guide to green manure. I use green manure as a cover crop every year so let me tell you all about it, and why you should be growing green manure too!
So, What Is Green Manure?
Green manure isn’t one plant, but a range of different plants. These plants are grown in your beds, often overwinter, before being cut back. Green manure is a natural way of improving the fertility and overall health of your soil.
This is where the term green manure comes from, as it is very similar to normal manure but is a living plant, hence the green in the name.
Green manure is grown from seed sown onto bare soil, you normally broadcast sow the seed very liberally to ensure good coverage. As all of the plants grown as green manure are very good at sprouting and also quick growing plants not much care is needed early in the plant’s life, or at all.
What Plants Are Grown As Green Manure?
There are a few plants that you will see time and time again as green manure, take mustard and red clover as two very prominent examples of this, there are, however, a whole heap of plants that can be grown as green manure, I will list some of the ones I know of below. (in alphabetical order)
- Alfalfa
- Birdsfoot
- Buckwheat
- Clover (Red, Crimson, Sweet, White)
- Field Beans
- Fodder Radish
- Forage Rye
- Mustard
- Phacelia
- Vetch
- Yellow Trefoil
As you can see, there are plenty of plants that can work as green manure, but they aren’t all the same. Some work better at other times of the year than others. Some are also better at fixing nitrogen in the soil whereas others will have a different benefit.
There are also mixed you can get that have a few of these plants in them. These are commonly sold as a spring mix or winter mix depending on when they are to be sown.
Choosing A Green Manure To Grow
If you have a specific soil problem then there may be certain green manure you want to grow to address those problems. There are also some green manures that are legumes and may want to be avoided if you use a crop rotation system or plan on growing other legumes in the same bed.
Some are better at weed suppression while others are better at breaking up heavy soil. There are also some types of green manure that can help reduce soil-borne diseases. Greenmanure.co.uk has an excellent chart with lots of different manures and their benefits.
I usually just grow a ready-made mix for overall soil health and nutrition, this is really easy to do and doesn’t require much thought or planning.
Sowing Green Manure
The sowing of green manure is really easy and takes no special care at all. You don’t even really need to worry about weeds as your manure mix should out-compete it.
Just broadcast sow the seeds all over the area they are to grow and give them a quick rake in. If it hasn’t rained for a while then water well but as you are probably sowing in spring or autumn this step won’t be needed for most of us.
That’s all there is to it really, just let your green manure grow now.
Growing Green Manure
Green manure is really simple to grow, which is one of the main reasons for growing it in the first place. I simply broadcast sow a lot of seeds and gently rake them in a little.
That’s all I do, I then step back and watch them grow. I always grow green manure as an overwinter crop so I just leave them to it before cutting them down in spring.
Digging In Green Manure
After you have chosen a green manure to grow (I recommend just going with a mix – unless you have a specific issue) and successfully sown it, and let it grow, it will then be time to dig in your green manure.
If you have never grown green manure before then digging it in is a step you could easily miss, so let me help you out.
So as the name would suggest, digging in means just that, digging the plants into the soil. This is a step that lots of people tell you that you need to do after growing green manure, but it is not one I do.
This is because I practise no-dig gardening, as made famous by Charles Dowding with this method of gardening you avoid digging your soil if at all possible. This in turn helps to improve your soil biology and overall health.
So if I don’t dig in green manure then what do I do? I chop and drop, another catchy gardening term for you. Again this is self-explanatory when you know what it means.
I chop the green manure back to soil level and then leave all of the plant growth on top of the soil and leave it to rot away into the soil naturally.
If I want to use the bed immediately then I will chop and drop and then add a few centimetres of compost (homemade or bought – it doesn’t matter) onto the soil. This gives your plants a really good start and means the roots are growing down into really nice, nitrogen-rich soil.
If you do want to dig your green manure in then simply grab a garden fork and turn it over mixing the cut growth into your soil.