Back to my roots (and tubers) – 2016

This post (a catch up on my experiments with all things subterranean) is a little later than I expected. Many roots and tubers are not lifted until after the first hard frost. This can hit in October or even September in Aberdeen, but this year there was nothing significant until January, so many plants just kept on growing. The other factor is that I am still recovering from a slipped disc I suffered last spring, which means that I have to ration my effort in the garden and watch the heavy digging.

Now, however, the harvest is complete and the results (as well as the roots) are in.

Some plants have by now become staples of the forest garden and my winter diet, including oca, yacon, skirret, Chinese artichokes and TPS potatoes. The slipped disc meant that some of these had to cope with very late planting and considerable neglect over the year. In some cases that meant that I only just scraped through the season with my planting stock intact. Fortunately, however, roots and tubers are forgiving plants. They carry generous reserves that allow them to grow quickly and smother annual weeds, so some of them did quite respectably all the same. Roots that I allow to self-seed in the garden, such as parsnips and salsify, did so with little fuss.

These are exciting times for the breeding of many root crops. My oca and yacon both flowered, but far too late in the season for seed, so I think I’ll have to leave those projects to collaborations with a more southerly distribution, such as the Guild of Oca Breeders. Yacon was once thought to be sterile, but the Cultivariable seed company in Washington State has managed to make a range of crosses (I can highly recommend Cultivariable as a supplier of most of these plants). Yacon seems to be an obligate outcrosser – that is, it needs two or more varieties grown together to produce fertile seeds. Anyone with two varieties of yacon and enough sunshine can join in the fun.

I had more luck producing potato seeds. Potatoes also struggle to fruit in time here, but the fruits can be ripened up on the windowsill like tomatoes and will reliably produce viable seed this way. It helps that TPS (true potato seed) varieties can be stunningly blight resistant, meaning that they get the chance to keep on growing right up until the frosts. There’s more on why you might want to grow potatoes and many other things from diverse seed in my post here.

burdock burrs

burdock burrs

Another reason I find for producing my own seed is that a number of root crops can be quite difficult to grow from bought seed as they do not store well and can have tricky germination requirements. My usual way around this is to grow my own, giving super-fresh seed that I often sow in autumn rather than spring. I managed to do this with burdock (Arctium lappa) this year. My saved roots sprouted to nearly 3m high and produced an abundance of the spiky seed heads that were the inspiration for velcro. The only drawback was that they tried to recruit me as a seed vector any time I passed. Burdock seeds may get so lodged in the coat of an animal that they stay with it until it dies, giving the germinating seed exactly the rich, fertile conditions that it likes. I love my plants, but that’s where I draw the line! Seeds that I collected and sowed in autumn are already germinating despite the snow on the ground this week, so I am already looking forward to a summer of kinpira gobo.

A plant that I have similar problems in getting viable seed with is Hamburg parsley so I am trying the same approach this year, with several choice roots saved for seed production. Turnip rooted chervil (Chaerophyllum bulbosum) benefits heavily from this approach too – I’ll post more about this plant soon.

Going back to the Andean root crops, I had promising results with two more. One that I tried for the first time was ulluku (Ullucus tuberosus) – also known as papalisa, ulluco, milluku, chugua and ruba. Ulluku produces both edible leaves and tubers that taste remarkably like beetroot. It put up with severe neglect and still cropped reasonably well for me. Undoubtedly the most striking feature of ulluku is its looks: the tubers come in a dazzling array of buttercup yellows, rose pinks, lurid magenta and porcelain white. Digging them up is like unearthing semi-precious stones. On the downside, centuries of vegetative propagation have left many lines of ulluku virus-ridden and reluctant to produce seed. Yet again, Cultivariable is having spectacular results in coaxing this species back into reproductive life, so I think we can expect to hear much more about this species in the next few years, with cleaned up tubers and new varieties.


Ulluku – yellow variety

The other new South American is mauka (Mirabilis expansa). Mauka is described on Wikipedia as growing at “cold, windy altitudes” in the Andes, which sounds just ideal to me! My mauka seeds rather surprised me by germinating immediately when I put them in the fridge to stratify, so I now have six little mauka seedlings growing away, just waiting to experience the cold, windy altitudes of Scotland (i.e sea level).

I have spent a while gathering plants of silverweed (Argentina anserina) from different locations and planting them in large pots outside. The reason for this curious behaviour is that silverweed is a very strong spreader, so without control you will tend to have just one extensive clone in your garden. I’d like to get seeds of this plant in order to try breeding it, since it is delicious and locally well adapted, but has the drawbacks of thin, straggly roots and that agressive spreading habit. A non-runnering variety would be favourite! I wasn’t able to collect any seed last year, but the plants all look healthy and I hope for better results this year.


Finally, a hill of beans. The bean family (Fabaceae) contains a number of species with edible roots, including talet (Amphicarpaea bracteata), hopniss (Apios americana), aardaker (Lathyrus tuberosus) and cairmeal (Lathyrus linifolius montanus). With me, the Lathyrus species have been disappointing: my aardaker has almost died out, while the cairmeal is growing quite cheerfully without producing anything that could be seriously regarded as an edible root. Neither the talet nor the hopniss made it out of the greenhouse and into the ground this year. Both seemed quite happy with this arrangement: both flowered and the talet produced seed. On the other hand, the hopniss produced only one tuber per tuber and I coudn’t find any of the subterranean beans that are meant to be the main yield of talet. Both are now lying low and, I imagine, dreaming of better weather and better health on the part of their gardener for the year ahead. Me too.

Previous posts relating to roots:
Winter harvests 2015
Back to my roots (and tubers) – 2014

Back to my roots (and tubers)

One of this year’s experiments in the allotment has been to try to get more starchy roots, tubers and bulbs into the forest garden. I haven’t had any straightforward, unmixed successes, but definitely some interesting leads that I want to follow up.

One fruitful (rootful?) source of edible roots is the Apiaceae or carrot family, home to the carrot and parsnip amongst familiar roots, as well as a large number of the plants that we use as herbs and spices (cumin, celery leaf, coriander, parsley, fennel, dill…). In particular, I was interested to try the native members of this family that have a culinary reputation: sweet cicely (Myrrhis odorata) and native hogweed (Heracleum sphondylium). Both have other edible parts (with some care in preparation required for the hogweed) but that’s a topic for another post. This time I wanted to get to the root of the matter.

I have tried sweet cicely root before. Like the rest of the plant, it has a strong aniseed taste, although the flavour moderates with cooking. Even so, it is a root to use sparingly in dishes with milder ingredients rather than to tuck into a plateful of. Mature sweet cicely roots are truly massive – and so deep that they are next to impossible to dig out whole. Unfortunately they are also not very nice: I only find the first year’s roots palateable, so I think that the answer is to have a few favoured plants as perennials for shoots, leaves and seeds and grow the roots as an annual crop.

I sowed a few rows in a couple of different sites with different seed sources, intending to select for the largest and straightest roots. The results were interesting. Site one was in open vegetable beds. The roots were a decent size but almost all quite heavily branched. Site two was quite shaded and yielded smaller but much straighter roots. I’ll have to do some experiments to find out whether this was genetic or due to the shade. Anyway, super-cicely is not on the horizon quite yet, but I’ll keep working on it.

sweet cicely roots

sweet cicely roots

The situation with hogweed is much simpler to report. The boiled roots were revolting. Yuk. I think I’ll be leaving them to the hogs from now on – although it does occur to me that I didn’t get to try first-year roots…

Other carrot-family roots include Hamburg parsley, which I’ll write about soon, and skirret (Sium sisarum), a perennial which bears a multitude of sweet, pleasant-tasting roots. Harvesting it involves digging it up, taking off some of the roots and putting the rest back in the ground. Turnip-rooted chervil (Chaerophyllum bulbosum) is a biennial with very pleasant-tasting but rather small roots. There is some evidence that strains with larger roots existed in the past so I’ve been growing the biggest of mine on for seed.


Another two candidates were South American crops that I have tried before years ago and which I decided to have another go at: yacon and oca. Oca (Oxalis tuberosa) is a tuber-producing relative of wood-sorrel, so the tubers have that lemony oxalic acid taste when they are fresh, but fortunately if you leave them in the light for a while it goes away. The big difficulty with growing oca at this latitude is that they only start to tuberise at around the autumnal equinox, by which time the frosts might be only a few weeks away. This year there were no hard frosts until November and I decided to try a little experiment. The plants had grown luxuriantly and I felt that they still had a lot to put into tuberisation if they weren’t completely killed by the frosts. I dug up one plant, covered two in horticultural fleece and buried a fourth under a thick layer of leaves. A couple of days ago I dug up the protected plants to compare yields. They were:

325g first plant
400g each for fleece-covered plants
550g mulch-covered plant

I imagine that a statistician would tsk at the size of my trial, but the results do suggest that covering the plants was worthwhile. The leaf mulch was more effective at insulating the tops than the fleece as well as being cheaper. Overall though, the yields are still rather disappointing for the space taken up. I don’t think that oca will really fulfil its promise in Scotland until someone finds a strain that starts to tuberise immediately. It isn’t too much to hope for as potato suffered the same problem originally.

Oca tubers

Oca tubers

Yacon (Smallanthus sonchifolius) is also frost-sensitive but had managed to put on a more impressive set of tubers than the oca by the time the frost hit. Like the related dahlia (also edible but not very nice), yacon crowns have to be brought inside to overwinter. It has two kinds of tuber: vegetative ones which will grown the next year’s plants and storage tubers which you can pick off and eat. The great drawback of yacon is that, like so many otherwise-promising plants in the daisy family (Jerusalem artichoke/sunroot, chicory, dahlia, elecampane, scorzonera), its roots are packed full of inulin, a sugar which can’t be digested by humans but which our gut microbes happily use, creating rather a lot of gas in the process… The culinary virtue of yacon tubers is that they keep their crunch even when cooked, so a little bit in a meal is great for adding texture, but I wouldn’t want to try to live on them.

yacon tubers

yacon tubers

The pea family (Fabaceae) is better known for its seeds than its roots, but there is a small number of tuberous species and one fascinating plant called talet (Amphicarpaea bracteata) that has adapted its seeds to work as tubers. This year I tried growing aardaker (Lathyrus tuberosus, also known as the Fyfield pea or Dutch mice: the Dutch name means earth-acorn) and cairmeal (Lathyrus linifolius, also known as bitter vetch or heath pea: the Gaelic name is pronounced like Carmel).

The aardaker gave a small crop of inch-long, tapering tubers that did indeed put me in mind of both mice and acorns. I would rather grow them on than lose any of them by eating them, but everything I have read about them suggests that they are delicious. The yield wasn’t exactly large, but it was produced in a very small space and, like all the peas, they have the added virtue of fixing nitrogen from the atmosphere, so I definitely think that this is one to keep an eye on.

Lathyrus tuberosus

Lathyrus tuberosus

By contrast, the cairmeal tubers were tiny. I couldn’t even take a photo that showed them properly. I won’t give up on it but might just abandon it for a couple of years and see how it gets on. There are advantages to cairmeal that make me want to keep trying: it is shade tolerant and has a long history of edible use in the Highlands.

Silverweed (Argentina anserina) is another plant that is reputed to have been used in the Highlands but has a bit of a problem in the yield department. I’ve had it in my lawn for years but decided long ago that its roots weren’t worth the effort of digging them up.

This year, I thought it would be interesting to take a closer look at the growth habit of the plant and transferred a few to pots of compost. They are strongly runnering so it can be very difficult to dig up a whole plant from the ground. In the autumn I shook off the compost and got a great view of the roots – with their swollen sections often at the end of the root but sometimes with the root carrying on beyond them. On the plus side, the roots taste great. I’m going to keep growing them in pots in order to (a) stop them invading the rest of my garden and (b) see if I can isolate individual strains and compare them.



Finally, some negative results. Two plants that I grow for their edible flowers, king’s spear (Ashphodeline lutea) and day lily (Hemerocalis lutea) are said to also have edible roots so in the autumn I dug up a few and tried them. Neither seemed worth it. The burdock (Arctium lappa) that I sowed produced next to nothing, as it usually does. I don’t quite understand this as burdock grows well in the wild here. I consoled myself with the thought that since they are in the daisy family they probably aren’t that much good anyway [UPDATE: I was wrong. See here]. My hopniss (Apios americana), another member of the pea family, did what it always does: it used all the resources in the one tuber that I planted to produce a total of one solitary tuber at the end of the year. I’m beginning to think that I could achieve the same result by pickling it rather than by planting it. It was a similar situation with the pleurisy root (Asclepias tuberosa). I’m experimenting with a few plants in this genus but mostly I think the climate is just a little too cold for them here. My attempt to grow Chinese artichoke (Stachys affinis) took rather a blow when the supplier sent me what turned out to be the related wild flower betony (Stachys officinalis) instead. Finally, my rampion (Campanula rapunculus), which is said to have long, fleshy, white roots, produced nothing but fibrous roots. From talking to others, this seems to be a common problem: has anyone out there ever grown rampion successfully?

rampion - where's my roots?

rampion – where’s my roots?

Other rooty posts: Chufa/tigernut; Wasabi, horseradish and friends; Self-seeded parsnips; Growing pignuts; Dog’s tooth violet

Next installment: Back to my roots (and tubers) – 2016