Green Manure: Why You Should Grow These Crops In Your Vegetable Garden

One of my biggest pet peeves in the garden happens right around this time of year when I’ve harvested an entire bed of crops and then it lies empty until the following spring. There’s nothing that annoys me more than an empty bed. Forever alone. Sob. While there are plenty of crops to plant over winter (more on that later),when you have a large vegetable plot, it is inevitable that some of the space in your garden will be unused at different times throughout the year. This is where planting green manure is a godsend for the industrious gardener. 

What exactly is green manure? Nope, it’s not as you might imagine, the product of a pony who’s had too much Thai curry (I’ll let that lovely image sink in for a moment); green manures are quick growing plants to sow in your garden where you have free space in between crops so as not to leave your soil bare. They are then dug back into the soil in as nutrient rich organic matter. Green manures also suppress weed growth in your idle vegetable beds and some varieties even fix nitrogen in your soil. Nifty! 

Green manures prevent the very upsetting but necessary task of covering up your veggie beds with black plastic or mulch over the winter months and look a lot more appealing than sheets of black plastic or beds full of weeds. 

This week, I harvested my onions and potatoes which leaves two of my beds empty until I plant something else in them. The soil in the onion bed isn’t in the best condition after a pretty bad year for onion production so it needs some love. I don’t want to plant my spring cabbages or overwintering onions in that bed as it doesn’t fit in with my carefully planned crop rotation. 

Rather than see this bed lying unused for the next five months, I intend to plant this bed with some green manure. There are plenty of different varieties of green manures and some are an attractive addition to the garden. In my recently harvested onion bed, I’ve decided to grow mustard as a green manure. Mustard is an excellent grower and can be planted between March and September which makes it the ideal for a vegetable bed that is lying idle in August. As a member of the brassica family however, it’s not the best one to use in a bed where brassicas will grow in the following cycle. I’ll let the mustard grow until mid-October then dig it into the top of the soil.

I’ve grown mustard and red clover as green manures before and found it a great way to use my empty raised beds that would otherwise be unproductive.

Benefits of Growing Green Manure

Fertilising

Green manures grow for about two to three months and are then dug back into the soil. This organic matter is absolute gold in a vegetable garden and means you don’t need to use as much of your precious home made compost and is another valuable way to fertilise your soil without resorting to chemical fertilisers (aka pure poison).

Weed Suppressant

Green manures prevent weeds from taking over a patch of soil. I’ve often found that even during the winter months, the weeds keep growing and I have to weed a lot in early spring before planting. Growing a green manure provides ground cover and prevents the dreaded weeds from taking over your beds between crops.

This is what happens when you dont cover up your beds properly. Bad Fiona!


Food for Pollinators 

If you’re a wildlife fanatic like myself and want to have a bee friendly garden, some green manures like clover provide much needed nectar for bees and other pollinators. I’d urge you to plant some clover during the summer if you have an empty bed. We need to do every little thing we can do to help our bees. Added benefit: clover is beautiful and reminiscent of childhood days spent picking it and sucking on the sweet stems  below the flower (yes, I did that, I was one of those kids).


Soil Improvement

Green manures improve the quality of  your soil which is of huge assistance when you’ve had a bad year and your soil is in poor condition. Planting a green manure helps to aerate soil which means far less back breaking digging the following spring. 

Nutrient Fixing

During autumn and winter, rain can wash the nutrients away from the top layers of your soil, which is why we cover our vegetables beds up during winter. A green manure will inject more nutrients into your soil and prevent those vital nutrients already there from washing away.Green manures from the legume family help to “fix” nitrogen in the soil during summer, meaning they take in nitrogen from the air and store it in their roots (further proof that plants are amazing).

Sowing Green Manure

Sow green manure direct where it is to grow. I find it best just to broadcast sow the seeds as opposed to sowing in rows as this cover more ground and provides better weed suppressant. Rake the seeds into the soil and water. The seeds usually germinate very quickly.

Digging In Green Manure
After three months of growth, dig your green manure into your soil while it is still alive and green (it kind of defeats the purpose to let it wither and die). Let the soil rest for about two weeks before planting anything as the green matter can make it difficult for seeds to germinate. 

Popular Green Manures

Mustard: Sow March-September. 

Grazing Rye: Sow September-November. A good choice for an overwinter green manure.

Red Clover:  Sow March-August. This attractive plant is great for pollinators

Buckwheat: Sow April – August. Grows well in poor soil.

Field Beans: Sow September-November. Another great over wintering green manure and as a member of the legume family is high in nitrogen.
Let me know how you do get on if you plant some green manure. Try tasting the clover too, it won’t kill you.

I don’t think I’ll be ordering Thai food for a while though….

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5 thoughts on “Green Manure: Why You Should Grow These Crops In Your Vegetable Garden

  1. Helen says:

    I’m a big fan of green manure. I use it to bulk up my compost rather than digging it in but either way I’d throughly recommend it. Phacelia is my favourite with its purple flowers, although it does self-seed very readily. On the other hand, that does mean I will probably never need to buy another packet of seeds again.

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