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Burdock without digging 🌱 One sheet of corrugated board, laid at an angle

Learning by growingAbout 7 min
Burdock without digging

🌱 "The digging looks like too much work."

🌱 "I grew some and snapped it halfway out."

🌱 "What I pulled up had split into two or three."

Hello, I'm Eiko. Eight years of growing vegetables organically and without pesticides, and a teaching licence in science.

Burdock is the crop home gardeners avoid most, for an obvious reason: the root goes straight down, over a metre. It needs deeply worked soil, and harvesting it is an excavation.

There's a way round it.

The point, up front:

Lay a corrugated sheet at an angle, grow on top of it, and you harvest without digging 🌱

The basics

Spacing is only about 10 cm — narrower than you'd think, because the root goes down rather than out.

And choose by length: the long-rooted types are what "burdock" normally means, reaching close to a metre. This article is about those.

How the sheet method works

Diagram: the root grows where it can

What this diagram says

  • A root grows where it can
  • Sow here ／ it can't go down ／ about 15 degrees ○
  • The grooves guide the root straight, so the shapes are even
  • Ordinary growing — dig a metre × ／ sheet growing — just take the soil off the top ○
  • You aren't pulling the root; you're making a direction available
  1. Make a slope of about 15 degrees in the ground
  2. Lay corrugated sheets along it
  3. Mound soil on top of the sheets
  4. Sow along the top of the mound

The root changes course

A burdock root sets off straight down — and meets the sheet.

Since down is unavailable, it follows the groove of the sheet and travels diagonally downward.

So there's nothing to dig

The burdock grows lying on top of the sheet. At harvest, you take the soil off.

Digging a metre down disappears from the job entirely.

And the grooves straighten it

A second benefit: the grooves guide the root. It bends and divides less, and the roots come out a consistent shape.

Don't stack the layers

Diagram: it divides where it collides

What this diagram says

  • It divides where it collides
  • × forked root — hard clods, stones, undecomposed organic matter
  • Ideas that failed — × three layers: too little soil; leaves overlap so photosynthesis is short
  • × growing in bamboo tubes
  • ○ single layer, with plenty of soil

The method takes up horizontal space, which makes "stack it two or three high and save room" an obvious thought. I had it too.

Three layers gives you thin burdock. Two reasons:

So: single layer, with plenty of soil. It takes space, and you can mound properly. A classic case of the space-saving idea costing the most.

Growing in bamboo tubes fails for the same reason. Too little soil fits in a tube, and you get roots like string. All three failures are the same failure: not enough soil. Burdock's thickness, not just its straightness, is decided by soil volume. Don't economise here.

Soil, and forked roots

Mix plenty of compost into the soil you mound, rather than using plot soil as it is. The reason follows.

A fork is a collision mark

"I pulled it up and it was in two." The cause is simple: the root tip hit something hard —

and divided at the point of collision.

So the answer is removing obstacles

Plenty of compost so the soil doesn't set hard. Pick out the stones. Don't use unfinished compost.

And protect it from heat

A mound of soil on a sheet is a thin layer: it dries and heats quickly.

With summers as they are now, this makes a visible difference.

Raise plants in cardboard tubes

Burdock hates being moved. It has a single taproot, and cutting it causes exactly the forking described above. Normally you sow direct.

When you do want plants: stand toilet-roll tubes together and use them as pots.

They're paper, so they go into the ground as they are — not a single root cut.

Stand the tubes up, put newspaper underneath, fill with compost. Something you'd throw away becomes the tool — and burdock needs a deep container, so the long narrow shape is exactly right.

Sowing

Thinly, because it's another light-requiring seed — same as shiso and chrysanthemum greens.

The science: roots take the path of least resistance 🔬

Diagram: the tip chooses where it can go

What this diagram says

  • The tip is choosing where it can go
  • Stone = can't go ／ hard layer = can't go ／ soft soil = can go ○
  • The same property — used well: it follows the groove and grows into a fine straight root ○
  • Used carelessly: it hits a stone and forks

Worth asking: why does the root turn sideways instead of backing up or pushing the sheet aside?

The answer: a root grows in whichever direction offers least resistance.

The tip has a mechanism that senses contact with an obstacle, and it abandons the direction it can't go and switches to one it can.

So you're giving it a choice

The sheet method is simply this: create a situation where down isn't available. The root concludes "sideways, then".

You aren't pulling the root. You're letting it choose.

And forking is the same thing

Hits a stone → can't go → goes elsewhere.

But there's only one tip, so the branches to either side each thicken, and you get a fork.

The same property, used well, is the sheet method; used carelessly, it's a forked root.

And what deep digging is for

Which puts "cultivate deeply" in its proper light: it's the job of giving roots a direction they can go.

Make the path before you add the fertiliser. When root crops disappoint, this is usually the reason ☺️

To sum up

You don't have to do all of it. Find one sheet and lay it at a shallow angle. That's the hard part of burdock removed 🌱

Thank you for reading!