Thwarting the Fennel Menace

Thwarting the Fennel Menace

There are a few pleasures in gardening that really make it feel worth all the work. Harvesting a huge batch of fat, happy potatoes is one. Picking up a cured gourd and finding it whole and hard and ready to be made into whatever project you desire is another.

But there is another gardening activity that is not at all about harvesting and food and goodness. No. I’m talking about the satisfaction that comes when you have completely thwarted an enemy.

My Greatest Foe

If you’ve read my blog before, you might have guessed that the enemy I mentioned is Wild Fennel. I literally named it The Worst Weed in the Bay Area. Back then, I didn’t have much encouraging advice. But that was then.

evil fennel coming up from a previously dug-up root
Like a zombie, the dug-up “dead” fennel emerges to terrorize the garden once more

Now I know how to kill it.


Without digging for hours in dry, unyielding clay.

The secret is Darkness.

Fennel under a sheet of black plastic
It looks awful, I know, but it keeps light away from the plant, which kills it completely

It’s not pretty, but few murder sprees are, amirite?

That Feeling of Victory

Today, I went to check on a few of my fennel torture bags. Yes, some were still holding on, and I carefully repacked them tightly.

But a few were dead. Fully dead. Dry as a bone. Ex-fennel.

And a few even came out of the ground complete, taproot intact. Look at the picture–that’s 2 feet down in the soil if I had tried to dig it out fully.

It was so satisfying pulling these jerks out of the ground intact. You can see the black plastic, yard staples, and the bowl used to cover one of the smaller ones.

How to Truly and Completely Eradicate Wild Fennel

fennel growing under a fence
Even in a tricky place like under a fence, plastic can be used to eradicate fennel organically. I used a staple gun to secure the plastic to this fence and it’s now clear of fennel.
Do you see any evidence of fennel now? It took over 8 months of plastic covering, but the deeply-rooted fennel is completely gone.


  • 6 mil Black Painter’s Plastic (NOT weed block)
  • Yard Staples
  • Yard clippers/trimmers
  • Staple gun (optional)
  • Black bowls from takeout or instant soup (optional)


  1. Trim the fennel down as far as you can go, removing all the material and composting it.
  2. Cover the stump tightly with the black plastic or a black bowl with holes punched in at least two sides near the earth (only use the bowl if the stump is small enough to fit totally inside underneath).
  3. Use yard staples or (near wooden fences) staples to secure the plastic or bowls in place. You are trying to eliminate light getting to any part of the plant, and stop any shoots from finding their way out.
  4. Keep an eye on your fennel darkness pods in case of escaping shoots. Remove any shoots that pop up, secure your light barrier again, and wait some more.
  5. Check occasionally after a few months to see if the fennel is dead. There should be no green or yellow material, and every part of what remains should be dry and brittle. That means success!

Stay Vigilant

While this method will take care of those old-growth fennel monsters, it does not stop new sprouts. Be sure to tear those invasive jerk babies out of the ground as soon as you see them. Fennel cannot be allowed to proliferate!

fennel taking over a fence
Don’t let fennel happen to you!

Bonus tip: This technique also works on Blackberry!

1 thought on “Thwarting the Fennel Menace”

  • THANK YOU!!! I read your previous article and it mirrored my wretched experience with fennel, but left me with little hope for the fennel forest our SF backyard has become. I bought the poison but was reluctant to use it so it’s been sitting in my garage for a year, unopened. I’m so excited to see you’ve found an organic solution, now it’s time to go to WAR with this beast. *cracks kuckles*

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