Fennel is one of those weeds that turns up all over the place around this city. It’s also a useful herb. As both weed and herb it has a potential role in my low-water zones. It’s in the Apiaceae (formerly Umbelliferae), the family of highly-flavoured umbrella-shaped flowering plants that includes carrot, parsley, celery, alexanders, dill, cumin, hemlock and many, many others both edible and poisonous. Fennel is considered edible in all parts.
There are three main types of fennel that get planted (and several varieties of each of those types). There’s just straight normal fennel, with its fine fronds and distinctively scented seeds and leaves. There’s bronze fennel, which is a brown/purple colour variant of the same thing. And there’s Florence fennel or finnochio, which has swollen leaf bases that you can eat as a vegetable. The latter gets sold regularly in our greengrocers and supermarkets now – it’s an old Italian vegetable, and between our old Italian settlers here and the new cooks like Jamie Oliver or Maggie Beer or even Heston Blumenthal promoting it, it’s become comparatively familiar. (I confess I define “comparatively familiar” as “it was ethnic when I was a kid but now it’s in Coles” – I’m old enough to have been born back when dinner meant meat-and-three-veg, one of which was potato.)
I am growing the bronze type. I don’t mind the finnochio bulbs, but I don’t love them either. For some reason, I just can’t get myself to accept that flavour as “vegetable”, and I don’t really enjoy it in fancy potato salads or steamed under salmon or any of the ways it’s being served nowadays by the cool kids. The non-bulb types I think are a little hardier, a little better able to self-propagate, they still have the seeds and leaves for use, they are a good height for screening sections of the garden away or giving floral/textural interest, and the bronze-purple shades in nicely with my other silvers and purples where I have it planted. The seeds and leaves work better for making sweets, which is how I prefer the flavour personally.
Fennel is of Mediterranean origin, and it’s old. Very old. Old enough to have been written about in all kinds of medieval quackery, Roman quackery, Ancient Greek quackery, Indian quackery… you get the picture. In fact some of what’s written about its medicinal values is possibly true, but not much has been properly tested so it’s hard to distinguish between actual properties and things it’s just been used for for so long that they’re considered “true by default” and “everybody knows that”. It is known to have a carminative effect – it improves digestion so you don’t fart as much. Its scent is derived largely from the chemical anethole, also present in aniseed and star anise. Its long human history means that there are also hundreds if not thousands of recipes that use it, from Indian cookery to absinthe – and those *have* been well tested for edibility and deliciousness. The seeds can be used dried, but fennel generally works better the fresher it is and the leaves pretty much have to be fresh.
Fennel grows quite well on coastal sands. It likes free-draining soil, preferably fairly fertile, but its presence as a weed across the more alkaline/less acidic sand zones of Perth suggests that the fertility isn’t absolutely necessary, it just makes better eating that way. It’s also drought tolerant, some varieties more than others. Mine is in an area that got watered once or twice a week across summer with a low-volume weeper pipe but which occasionally went for two weeks between waterings. It could probably have coped with less water or perhaps less-frequent-but-deeper waterings given that I’m not trying to grow the bulb variety. It has established itself as a weed in several Mediterranean-climate-countries so is obviously able to survive our summers with no watering – while it sets huge amounts of seed which germinates freely with any kind of soil disturbance (a very “weedy” quality), the plants don’t usually flower in their first year so it must be able to live OK through at least one summer in order to sow the next generation. (Here’s an entertaining PDF from California for weed removers, showing just how hard it is to kill. Though it hasn’t been considered significant enough in this country to make it into the weeds.org.au database, which implies it hasn’t got into cropping areas particularly and has stayed nearer to the coast.)
As to how it plays with others – that’s not as great. It can end up forming very dense, light-blocking thickets. Its roots aggressively claim its space. It may also have an allelopathic action – discouraging other plants from growing. Together that all means that as a crop it’s less susceptible to weeds, and as an ecosystem partner indicates that it will drop plant diversity in its immediate vicinity so is better suited to clustered designs in managed systems (and needs removal in native systems). Companion-planting sites happily and consistently state that “fennel doesn’t have friends“. Having said that, the chemicals in fennel have been shown to inhibit soil fungus and fungal diseases such as those that affect tomatoes, and it is very good at attracting beneficial insects into a space, predators and pollinators alike. So it might work grown as a temporal spacer in a fallow bed, or in an isolated space or pot just harvesting the leaves to make garden treatments. It does cross-pollinate easily with other plants of the family, such as carrot, celery or dill, so needs to be grown separately from those in order for any of their seed to be saveable for more plantings.