Have you planted a green manure crop this year?

A few weeks ago we recommended planting a green manure crop as one of the fastest and easiest ways to improve your soil before you plant fruit trees. This week we’re showing you what the crop should be looking like by by now, and what to look for.

A green manure is a fast-growing crop of (usually) annual plants, and it’s one of the quickest ways to improve soil fertility and add organic matter to your soil.

The last couple of times we’ve planted new orchards, we’ve first put in a green manure crop before we’ve planted the fruit trees because we’re always aiming to increase the biodiversity under our fruit trees—it’s one of the best ways we can provide the right habitat for useful insects that help us keep the pests under control.

Sas planting a green manure crop in the nursery
Sas planting a green manure crop in the nursery

This year we planted a green manure in the block where we’ll be planting the new nursery in winter. The seed mix included grasses, legumes (nitrogen fixers) and herbs – grasses to add bulk organic matter to the soil, the legumes to add nitrogen, and the herbs to add a diverse mix of nutrients. If you’re not sure what seed to choose, you can check out our recommended plant lists (and even some suppliers of organic seed, if you’re in Australia) in this short course.

We’re always aiming to increase the biodiversity in our soil – it’s one of the best ways we can provide healthy soil to grow trees, as well as habitat for useful insects that help us keep the pests under control.

The more diversity you can get into your garden, the healthier your fruit trees (and all your other plants) will be. And if you’re growing your own food, you definitely want that food to be as healthy and nutrient rich as possible.

Clover starting to grow
Clover starting to grow

It’s always a good sign to see lots of clover seedlings coming up. We particularly like having clover because it’s a nitrogen fixer (taking nitrogen from the air and putting it in the soil where the trees can use it).

Clover is quite spreading and so out-competes less useful weeds, and it self-seeds so it will persist in the orchard for years.

Experience has shown us that even though we plough green manure crops back into the soil before we plant the trees, plenty of clover seedlings will still come up, and over time it will gradually spread throughout the orchard floor.

A bean plant in the green manure crop starting to grow
A bean plant in the green manure crop starting to grow

Before we plant the new nursery in July, we’ll be turning the crop in. We use a rotary hoe, or the disc behind the tractor, but in a home garden you can either turn it in with a shovel, or just mow it and leave it on the soil – it’s not quite as good, but the worms will eventually take that lovely organic matter underground for you.

Getting ready to plant a new tree
Getting ready to plant a new tree

One of the unfortunate consequences of using large macinery like a disc is that disturbing the soil so comprehensively provides the perfect environment for opportunistic weeds such as capeweed (below).

Beautiful but unpopular capeweed
Beautiful but unpopular capeweed

We appreciate all our weeds, and even the much-despised capeweed has many fine qualities, but it’s not the plant we prefer to see in the orchard, as it tends to out-compete more useful plants, without conferring the benefits of a nitrogen-fixer.

Just one word of warning – if you are going to turn in your green manure crop, try to leave at least a couple of weeks between doing so and planting your trees, because the rotting green material can become quite hot as it breaks down, and you don’t want to burn the roots of your baby trees!

So in a classic case of “do what we say, not what we do”, here’s our top 4 tips for looking after your soil when you plant your fruit trees:

  1. Plant a green manure crop
  2. Turn it into the soil at the site where you are going to plant a tree, preferably a few weeks before you plant
  3. Disturb the soil as little as possible when planting the tree
  4. Re-seed the area with preferred understorey plants.

Should you spray organic fungicide in autumn?

A peach bud in spring with copper spray
A peach bud in spring with copper spray

A lot of people don’t think “organic” and “spray” go together, but actually there’s a couple of relatively ‘safe’ sprays that certified organic growers can use, under strict organic standards.

The only sprays we use are organic fungicides — a little bit of copper, and elemental sulphur — because in a wet season they can make a huge difference in preventing some particularly nasty fungal diseases if you use them in spring.

An apricot with brown rot
An apricot with brown rot

Some people also recommend spraying fungicides on fruit trees after the crop has been picked in autumn, to clean up any residual disease, but this is a bit more controversial.

So, when is the right time to spray? Do your fruit trees really need an autumn fungicide?

The answer is … sometimes!

In our short course Keep Your Fruit Trees Free From Disease we detail those diseases that can benefit from an autumn spray of an organic fungicide, under certain conditions, like brown rot.

So we certainly don’t rule it out, and it can be a useful part of an overall strategy for cleaning up some diseases. However, in most reasonably healthy trees, you don’t need to routinely use a fungicide.

And that’s a good thing, because even organically allowable sprays can have an impact on the environment, particularly the soil, and you should only ever use the minimum amount necessary, and strive instead for a really rich biodiverse garden where natural immunity will be at its highest. (And you should never use chemical fungicides.)

If you’ve had a dry season – as we have in central Victoria this year – there’s been very little fungal disease.

Remove this diseased wood when pruning for good disease control
Remove this diseased wood when pruning, for good disease control

Under these conditions our strategy includes pruning any diseased wood out of the tree, and totally removing it from the tree and the orchard floor, but we won’t be needing to put on a spray at all. Excellent!

Soil prep before tree planting

It’s time to do some soil preparation before you plant your fruit trees.

Lush green manure crop
Lush green manure crop

It’s a great idea, if you have time, to plant an autumn green manure crop. This is particularly important if:

  1. you have poor soil
  2. you don’t have enough topsoil
  3. you’re planting a tree into an area where a tree has died or you’re aware there has been disease, or
  4. you’re keen to give your new trees the best possible start in life.
Clover is a great addition to a green manure mix
Clover is a great addition to a green manure mix

Here’s how to do it. You can either buy a green manure mix, or make your own—you can find both autumn and spring plant lists in our short course Build Soil Fertility with Green Manures.

We buy the seeds separately and mix them together in a bucket before sowing. You can also add some fine sand into the mix to help spread it evenly.

Mix the seed well before sowing
Mix the seed well before sowing

It’s a good idea to lightly work the soil up (by machine or digging with a shovel) before you spread the seed, then rake lightly to cover the seed with a fine layer of soil.

The idea is that you wait until the ‘autumn break’ before you plant, i.e., after the first decent rainfall event that signals the end of the summer dry. Depending on your area and climate, hopefully this has already happened and you’ll get enough natural rainfall for the crop to grow. 

If you live in a particularly dry area or are currently experiencing drought, it’s still worth trying to get a green manure crop started, but it’s only really practical to do this on a small area, because you’ll have to irrigate the crop to get any benefit.

Select your tree sites first, and then work the soil and plant the green manure crop in an area at least 1 square metre at each tree site.

Once the crop has grown (ideally to at least a few inches tall), turn it back into the soil. It’s good to do this a few weeks before you plant your fruit trees, to give the green matter a chance to break down in the soil.

It’s a pretty straighforward practice, but the benefits to the soil are enormous. If you use the right mix of seed you should be adding a wonderful nutritional boost, as well as some bulk material to increase the organic content of your soil and provide lots of lovely food for the soil microbes.