I was being a bit of a pig in the allotment recently. Wild boar are one species that definitely didn’t get the memo about no-dig gardening. They have worked out one essential fact about the winter forest: the ground is where all the good stuff is. Their rootling behaviour – essentially ploughing up the ground looking for hidden bounty – looks destructive, and in some ways it is. Where densities are high they can cause an 80-95% reduction in herbaceous cover and the local extinction of some species. In other ways, their activity aids the health of the forest. Like any sensible pig, they prefer to target abundant species where they can be sure that all that work will be rewarded (you try digging up the earth with your nose, after all). As such they preferentially target plants with imperialistic tendencies, such as bracken and willowherb rhizomes or carpeting bulbs such as bluebells. This knocks back these aggressive spreaders, making space for a greater variety of species, and a number of studies have shown that over the long term species diversity is higher in areas with wild boar than in those without.

Similarly, in the forest garden, there are some crops where a good rootle is the only way to harvest them at some times of year, and the resulting soil disturbance helps to make room for a range of self-seeding species that tend to get crowded out in entirely undisturbed, perennial communities.
One of these is turnip-rooted chervil, or plain root chervil (Chaerophyllum bulbosum), a biennial root vegetable in the carrot family. If you’ve never heard of it, that’s probably because it has a few oddities in its life cycle which mean that it has never been cultivated widely. The first of these is that the seed needs stratification (winter cold) in order to germinate, and loses its viability very quickly in dry conditions (like seed packets). This means that fresh seed needs to be collected every year and sown very soon after, in the autumn. This makes growing it in rows in a crop rotation quite awkward. One option is to simply allow it to self-seed around the garden, which it does very readily and which eliminates all the worries about sowing and stratifying.
The second problem is that it sprouts early and dies back early, generally at the first hint of dryness. When it dies back it does so without leaving a trace of where it is. This isn’t a problem in labelled rows, but definitely is when the roots have planted themselves randomly around the place. It isn’t helped by the fact that many people reckon the the flavour of new roots is poor compared to ones that have sat in the ground for a few months in cold conditions.

All this leads to two main strategies for growing root chervil. The first is to sow it in annual beds in autumn, well marked and labelled. It starts to germinate here in early March, well before most crops. It then dies down by June, giving room for another crop, perhaps something like oriental greens which benefit from a late sowing so as not to run straight to seed. Finally it can be harvested over the winter. Some gardeners report problems with rodents getting at the stored roots, in which case a month in the fridge is also enough to improve the flavour. I find that chervil roots have a starchy, chestnut-like flavour that I enjoy a lot.
The other option is to let the plants take care of the sowing themselves, but this means that you are likely to have very little idea of where exactly they are by the time you want them. Until, that is, the roots have to give themselves away in order to grow for the new season. This is when you can harvest a great delicacy. A quick rootle will give you a pile of roots with young growth attached. There is no need to separate these as both parts are edible, just wash them well. By this time the flavour of the root has changed completely. The starch has been broken down into sugars, mobilised for growth, and the taste is now somewhat carroty and very sweet. It is impossible to get them out without a degree of soil disturbance, but, as the wild boar demonstrate, that is not entirely a bad thing in the forest garden.

Whenever you dig them up, it is worth keeping the best roots to transplant to another bed for seed production. The roots show a lot of variability, in size, length and form. The default seems to be a round shape, presumably explaining the ‘turnip-rooted’ part of the name, but a proportion have an elongated, carrot-like shape which seems to be associated with higher yields. Given that you are likely to have to maintain your own seed line if you want to grow this vegetable at all, you might as well take the opportunity to improve the stock and adapt it to your own conditions as you go.

I am always astonished at what a vigorous shoot comes out of a little chervil root. From a root usually no more than a few centimetres long they throw up seed stems over three metres tall. These can be very dense and with little leaf, so most of the nutrients required must be coming out from the root. This matches with the starchy flavour and a dry weight that is about 40% of it’s fresh weight. Chervil roots are clearly very dense nutrient stores. As such they could be seen as contributing to nutrient storage in the system as a whole. I am never too worried about surplus chervil roots that pop up and run to seed in unexpected areas of the garden: they are easily pulled out and put on the compost heap and don’t seem to bother the plants around them excessively as they are running on stores.

There is more on TRC at:
https://www.cultivariable.com/instructions/root-crops/how-to-grow-root-chervil/
https://hort.purdue.edu/newcrop/proceedings1990/V1-422.html