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Is bronze fennel alleopathic?

I'm trying to create something of a prairie-style planting scheme in my garden. I need an umbellifer-type plant for shape and texture contrast and had my heart set on bronze fennel until reading that some fennel has alleopathic qualities. I'm not so keen to give up on the idea and have a few questions for those who grow it:

Is it really badly alleopathic (to the extent that it will be encircled by a veritable wasteland of withered flowers, or is the effect mild to the extent that it might be tolderated)?

Is the alleopathic nature as true of bronze fennel as it is of foeniculum vulgare, or is the effect reduced or exacerbated?

Is this effect evident with grasses as well as other plants?

If I planted it alongside established perennials will they be ok (ie is the effect only seen on young plants / seedlings by impeding their emergent growth) or can i expect to notice a reduction in their health in subsequent years?

How about planting it in a large pot and submerging the plastic pot into the earth like i do with the mint that I want to control? Would this help?

Thank you for any help you can offer with this....I've been scouring the net for a long time but have been unable to find any conclusive evidence from gardeners. 



  • K67K67 Posts: 2,507
    Er... what's alleopathic?
  • josusa47josusa47 Posts: 3,530
    I have bronze fennel which I grew from seed I collected at the local park.  In both places, it grows in the ground, closely surrounded by lots of different flowering plants, which don't seem in the least affected by the fennel.  It's a lovely maintenance-free plant which gets bigger and better every year.

    You can collect the seeds to use as a spice, or grow them like cress on a windowsill for a tasty sandwich filling.
  • BijdezeeBijdezee Posts: 1,484
    I never had that problem with it but I have to say that it seeds everywhere and has very deep roots that makes it hard to remove. Personally I prefer Dill as an umbellifer type. It's your decision of course. Perovskia looks good in prairie style planting. 
  • ButtercupdaysButtercupdays Posts: 4,409
    I would suppose that the inhibiting hormones are secreted  by the roots and so would only affect the area occupied by them. As the fennel foliage is generous and drooping you would not see much effect.
    I certainly don't recall any problems with the green fennel I had a few years ago and I've got 6 pots of bronze fennel seedlings in my greenhouse right now, which will go in my veg garden to help attract beneficial insects :)
  • BijdezeeBijdezee Posts: 1,484
    edited May 2020
    Just like to add that the unwanted seedlings of my bronze fennel pop up in the middle of perennials, shrubs and herbs which are unaffected by it leading me to believe that it is not alleopathic.
  • Thanks for the responses. All really helpful.
  • WilderbeastWilderbeast Posts: 1,413
    I have 6 large green fennels and they are surrounded by perennial plants old and new, certainly can't see any effect on them at all. I agree with others they self seed profusely and are giving me a headache with weeding. Tried to move 1 this spring and gave up as it wouldn't budge a bit must have massive tap roots 
  • NollieNollie Posts: 7,053
    I would be a bit careful with fennel, of whatever type, it can be pretty invasive and difficult to get rid of as others have already pointed out, but it does attract beneficial insects, so that’s the balance. It has deleterious allopathic effects on many plants but especially in the vegetable garden - especially bad for beans, tomatoes and kohlrabi. The root exudations affect the roots of nearby plants, so it is what is happening below ground that is the concern. Some plants also shed complex allelopathic chemical compounds from their leaves too, whether after rain or through leaf drop, but not sure if fennel does this as well.  Best to keep it in a separate bed than the veg, @Buttercupdays.
    Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
  • LoxleyLoxley Posts: 5,238
    edited May 2020
    Patrinia scabiosa would be an interesting alternative. Native Daucus carota is lovely as well IMHO, 'Dara' has nice pink flowers that fade to purple. Then there are the Ammis… these things are a bit more airy and open than fennel which forms a bit of a dense mass (although lovely).

    Keep us updated re your prairie style planting, it's a style I really like.
  • nutcutletnutcutlet Posts: 27,162
    Bindweed grows up through it OK :) 

    In the sticks near Peterborough
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