Hi, Geoff Lawton here.
I want to talk to you about weeds.
Plants in the wrong place, they say.
Well,
are they?
Or are they just a response?
Are they just a symptom
and not a cause of a problem?
If we
look carefully,
and observe where weeds fit in
to operative sequence, we can read the landscape.
We can rebuild ecosystems by speeding up that sequence,
moving it forward in time,
and we end up in an abundant, productive system
simply by understanding weeds, without prejudice,
without assumption, but just pure observation
of the facts that weeds are some of our best friends.
Here we have a classic case of compaction.
And in this case, it's ducks, an oversupply of ducks.
And in any square meter of ground,
there can be thousands of different types of seeds
that can germinate,
but the germination condition
determines what does germinate.
And when you get compaction,
you get decompaction weeds that germinate,
dandelions in lawns.
In this case,
this is Australian weed called Paddys' Lucerne.
And it's a
decompacter.
It has long taproots.
So if you compact,
the opposite effect happens.
You get a decompaction root germination weed.
And this is a really
wiry, little plant.
It's pretty tough.
It puts its roots down.
Nature's in no hurry.
It can wait for this plant to die
and these long, decompacting roots
die and the ground
and create compost corridors
to decompact the soil.
Now we could cut these off
so that happens faster,
or we could spike the ground
and relieve the compaction.
Either way, we know from this indicator,
that we've had ducks on the ground too long,
and they've caused compaction.
It's the same with any animal
or any vehicle.
You get the same response from the decompaction weeds
wherever you live.
And that's just a matter of
reading the landscape through weeds.
Another germination condition is when the soil is too loose.
This little blue-flowering weed here is a good
variety of
hairnet root.
It creates a hairnet that actually holds together the soil.
So this is a germination condition
the opposite to compaction.
This is a soil stabilizing element,
and if we carefully pull it up,
you'll see the whole thing is hairnet.
There's soil being held together at the surface.
Now it's not compacted, it's too loose.
It's vulnerable to erosion.
So the type of weeds that germinate in this condition
function
as
loose soil traps,
holding together the soil for stability sake.
Once it becomes stable, once this mulch is down
as the weeds go through their lifecycles,
then the soil gets stable, it's bonded together
with organic matter,
and it goes onto the next cycle.
These are things that we have to understand.
Here we have a classic bracken fern.
Now bracken ferns harvest potassium.
And potassium,
K on the element scale,
burns off in a fire.
You get potassium through all green material.
When we have a hot fire, most of the potassium
goes up in smoke as the green material burns off.
A little bit is left as fine ash,
but that very quickly leaches,
leaving the ground depleted in potassium.
Now the plants that germinate then
are specific specialists that can harvest potassium
where it's in very short demand.
And a classic, worldwide
is the bracken fern.
It has a fibrous root.
And it's a classic harvester of potassium.
If you analyze the bodies of these ferns,
wherever they appear, in any of the climates,
you can guarantee that they're high in potassium,
and if they're growing, there has been a fire.
And that fire has left the ground depleted in potassium.
Now if you cut these and mulch 'em to the ground,
they will reduce
the germination of bracken itself.
So if you cut a patch of bracken
and slash it and mulch it to the ground,
it will reduce by a meter.
If you burn it
and turn it into ash,
you'll deplete more potassium
and it will spread by a meter.
These ferns are spread by fire
depleting potassium,
and as they return potassium to the soil,
they deplete and become, more or less, unemployed.
Their job's done.
Their function
is to replace
the depletion
through the fire.
So this is a sequence you can read
all the way through the forests of the world
where we are destroying forests
and ravaging the landscape with fire.
So it's a very useful,
lifesaving way of reading the landscape.
One of the classic weed functions of the world
is to repair the soil when it's depleted of fertility
with its base element, nitrogen.
And this is done by the peas and bean family,
and right up through
the same family within the trees.
This is how landscape is repaired
right through to the forests,
is the classic legume tree, leaf patent here.
And here's another one.
There are many types of leaf patents.
But these plants have special ability,
to partner with
a microorganism,
a rhizobium bacterial colony in the soil,
and they all have different rhizobium bacterial colonies.
This plant here has nitrogen nodules at the surface,
where its roots are poking out.
And these tiny, little nodules
are a colony of organisms
that are fed by the plant.
The plant's fast carbon pathways
brings in photosynthesis
and feeds these organisms with starch.
In return, the plant is given nitrogen
and that quickly relates to protein.
So most of the really good forages and feeds
are also high in nitrogen
because they're in that pea and bean family
that have the ability to
transfer
nitrogen into the soil.
And this is a great way to fertilize the ground
and it's the way nature recovers.
So right around the world,
you can use this classic weed example
as an indicator
that the land needs to be repaired
and the land needs to be given back for what you take.
And that is why traditional farmers
partner with nitrogen-fixing plants.
In a crop garden, where we want production
coming out all the time,
we know we've got to keep feeding the soil.
We know at times, we're going to exhaust the soil.
We going to bring in compost.
We bring in organic fertilizer,
but we're in a special race with the weeds,
especially around the footpaths and the edges.
So if you replace the weeds
with a designer weed,
with a cover crop, a plant that fixes nitrogen,
it takes up all the space.
There's hardly any rooms for weeds.
And these plants,
these plants
fix nitrogen.
There's nitrogen nodules here.
So there's nitrogen going in the soil.
And the top of the plant here,
that can go down as mulch.
So we've got green manure mulch.
We've got nitrogen in the soil.
We're leaving structural roots there.
That's got to be a better deal than trying to work with
unruly weeds, difficult weeds.
Design your own weed system, beat 'em at their own game.
So when we understand how weeds control the ground
and develop sequences and change over time,
we can design a sustainable world.
We can work with those natural systems.
We can harmonize
with the ecologies that repair the Earth
and go through to permanence.
And that permanence can be productive forever,
so we can all
enjoy the journey.