SF Bay Gardening

Update 09/17/2021: I found the best way to kill fennel! Read about here: Thwarting the Fennel Menace

A woman taking a walk past my yard once said to me, “Oh, that’s a shame, it smells so nice!”

That woman, in her early sixties, moving slowly past me, tapping her cane as she plodded along, probably didn’t realize how close she came to being brained with a shovel.

I was, at that moment, using said shovel to vainly attempt the removal of a clump of fennel root that had tucked itself neatly next to my new fence. It was probably the 6th clump I had worked that morning, and my inner arms were speckled and itchy with the contact dermatitis fennel fronds give me. My muscles were wrought with the effort. I was sweaty, exhausted, and frustrated.

Instead of killing my neighbor, I nodded to her with incredulous eyes, and then grunted as I placed a booted foot on the shovel and started rocking it back and forth again, trying to wrench the gnarled root from the earth.

Wild Fennel is an invasive species that loves our easy-going weather. From the cute little whale’s-spout-sprouts you might not think to remove from your garden to the nine-foot-tall spider-web covered seed-pod-shedding stalks, they truly thrive here. And no, this isn’t the tasty kind of fennel–this variety doesn’t bulb. The only edible parts are the feathery leaves (apparently they taste good with fish?) and the seeds (which you should never let happen, so don’t even think about it!).

And they are impossible to kill.

When they are tiny sprouts, you can pull them up and they’re kaput, yes. Even those larger, single-stalked plants can be removed from wet soil in the spring. But once those roots go deep, breaking into the dry clay soil, and then start throwing up more stalks, you are screwed.

To kill fennel without using horrible herbicides (which I refuse to do), you need to remove every. single. piece. You can’t use a tiller. You can’t just “cut it back.” Covering it up does nothing, as it will continue to grow in complete darkness under rocks, pavement, etc. You have to dig each plant up and out. Leave nothing behind. Do not compost the roots yourself–they’ll grow again. Like zombie weeds.

Back when we had that previously-mentioned fence put in, I was still naive as to the extent of fennel’s abilities as a weed. I remember seeing the contractor clear the area, and the ground looked pretty bare when the fence initially went in. But after a month or so, the clumps beneath the earth rose out with new green sprouts. I felt like the father in Poltergeist when the corpses start rising from his yard.

But I digress.

What can we do about the fennel menace, you ask?

1. Don’t let it go to seed. Never EVER. Even if you just trim it down and don’t dig it out, make sure those seeds don’t end up in your yard.
2. Pull up sprouts often, and take care of small plants as soon as you find them. Once they are larger and deep-rooted, they are MUCH harder to eliminate.
3. Dig out what you can, as often as you can.
4. According to the California Invasive Plants Council, repeated cutting back, with short intervals in between, can exhaust the root system and eventually kill the plant. I’ve never managed to keep up with methodical cutting back, so I haven’t seen this in action, or how long it takes.

I’m sorry I can’t give better or easier advice, but fennel is like the zombie apocalypse of gardening. You won’t be able to eliminate them all, so just kill as many as you can before they get you.