What's wrong with fennel?

[fruitfly]

I've planted some fennel seeds in trays and I've just read, in an article about companion planting, that you shouldn't grown fennel near any other food crops but it doesn't say why not - what harm can it do??

[diggernotdreamer]

Fennel is cited as being an allelopathic plant, i.e. it prevents other around it from thriving, it does become a very large plant in any event and is a very good structural plant, the bronze variety of the seed fennel is very attractive and is a great plant for attracting hoverflies to the garden, florence fennel is a shorter plant and has smaller flowers.

[Brewtrog]

It does grown into a monster (or mine did at least). But the rosemary and chives near it still thrived (then again they are pretty hardcore growers).

[Green Aura]

It grows happily in amongst other herbs and fruit bushes here.

[diggernotdreamer]

I think it is more of a problem when you direct seed into an area with annual things, I have grown it really happily with other perennial herbs

[Weedo]

Hi

From my limited knowledge Fennel is allelopathic to a fairly high degree as far as greatly reducing germination of the seeds of other species rather than, like some wild sages, actually killing existing growth. I would guess that anything of a reasonable size planted with fennel would survive and anything already there would also. There would probably be a greater effect if you tried to plant seeds of something in a bed that had fennel in it the previous year. Fennel grows feral and weedy in the moister southern areas of Eastern Oz and it does not seem to have a widespread effect, mostly just around the plant.

Allelpathy is a complex thing, I am currently involved (on the edges) in a research project investigating allelopathic effects of eucalypts as potential alternatives to herbicides. We know that grass & crops will grow up to the trunk of a redgum but not a yellow box and that blue gum will not tolerate anything else living close to it. After testing some 200 euc species we have found effects from different species vary from weed species to weed species, some have no effect at all and others are very strong. So far 6 species are showing promise, not only as herbicide replacements but also as fungicides.