I’ve just posted my list of seeds collected in 2017. Ones that might be of particular interest this year include various crosses between Daubenton’s perennial kale and some of my favourite annual kales, a particuarly nice wild-collected raspberry that I have named ‘Sunset’, and a fabulously varied runner bean grex. Like last year, I’m offering the seeds on a gift economy basis, for swap, donation or pay-it-forward.
‘Dynamic accumulators’ are often promoted as an essential ingredient of organic gardening and forest garden design. I’ve planted them myself, but the longer I grow my forest garden the less I find there to be any point to them, so I’d like to try to answer three questions in this article. First, what is a dynamic accumulator anyway? Second, do they work as advertised? And third, do you need them in a forest garden?
What is a dynamic accumulator anyway?
Let’s start with Wikipedia. According to the entry current at the time of writing, “Dynamic accumulators are plants that gather certain micronutrients, macronutrients, or minerals and store them in their leaves.” The trouble is that there’s a shorter term for this kind of plant. It’s a “plant”. All plants do this so by this definition dynamic accumulators aren’t a thing.
Trying to get back to the source of the term, all roads seem to lead to Robert Kourik’s book Designing and Maintaining Your Edible Landscape—Naturally (1986). Kourik included a list of ‘dynamic accumulators’ – plants that he understood to be high in particular nutrients . The purpose of the list was to give some guidance as to what different plants might be contributing to the compost heap and which might be best for producing high-value compost. The trouble is that Kourik himself seems to have disowned both the term and his original list. For more detail, see The Facts About Dynamic Accumulators, an excellent article from the Permaculture Research Institute tracing the origins of the term.
Dynamic accumulators, then, rather resemble the monster in Mary Shelley’s Frankenstein. Rejected by their creator, they roam the countryside looking for purpose and acceptance. Have they become, as Frankenstein’s creation eventually did, embittered and malignant or have they, as the monster dreamed of doing, found their own way to becoming a useful and accepted member of society? Let’s move on to how those authors who still use the term, almost all of them in the field of permaculture, define it. Taking a survey of these, three key ideas seem to contribute: hyperaccumulators, nitrogen-fixers and deep-rooted plants.
Hyperaccumulators are used in the fairly well established field of biological remediation of polluted soils, in which plants are used to pull pollutants out of the soil, before being cut down and disposed of at a hazardous waste site. As a result there is a reasonable body of research into plants that are particularly good at taking up different nutrients and these have acquired the term ‘hyperaccumulators’. Incidentally, this is the only use of the term ‘dynamic accumulator’ that I can find in the scientific literature.
Nitrogen fixing is quite uncontroversial. Some plants form an association with bacteria that allow them to turn nitrogen gas in from the air into forms of nitrogen that plants can use as fertiliser. Most of these are in the massive legume family (Fabaceae), which runs from weedy climbers to great trees. A few, such as alder (Alnus) belong to other groups collectively known as the actinorhizal plants.
Finally, plants with deep roots are often proposed as dynamic accumulators, with the idea that they will take up nutrients from deep layers of the soil, otherwise at risk of being washed out of the system entirely, and return them to the surface layers where they will become available to other plants, either through leaf fall or through the gardener actively cutting them for mulch or compost.
Some definitions of dynamic accumulators take them to be identical to just one of these groups. Others, including the one on Wikipedia, attempt to ram them together into one concept, ignoring the fact that few plants belong to all three groups and the most popular ‘dynamic accumulators’ almost never do. Is this a case of grouping together ideas that would have much more clarity separately or is there a fuller picture that the all contribute to? Let’s find out in practice.
So do they work?
In some places dynamic accumulators seem to be assumed to have almost magical properties. In one blog I read the author expressed confusion at the fact that her crop plants were struggling despite the large and vigorous dynamic accumulators she had growing all through them. It’s almost like trickle-down theory for plants. Dynamic accumulators are imagined to create nutrients out of nowhere and share them freely with surrounding plants. In reality they are almost by definition plants that excel in grabbing nutrients and keeping them for themselves. Whisper it, but another name for dynamic accumulator might be ‘weed’. If we want to put them to good use it will have to more intelligently than this.
Using plants as a means of moving nutrients around requires us to ask some questions. Which nutrients do we want to move? From where? To where? What for? However you define them, dynamic accumulators are plants that take up space, light and water. Unless we can give good answers to these questions there is no point in using them.
The hyperaccumulator model
This is why the comparison to hyperaccumulators is misleading on several counts. Firstly, the hyperaccummulators that have been researched so far have been identified for their ability to accumulate problematic, toxic elements, not the ones we want in our gardens. There might be equivalents for the more useful nutrients or there might not be, but in any case the hyperaccumulators so far identified aren’t much use for productive gardening.
Secondly, we should remember that hyperaccumulators are used for taking chemicals out of soils. Where there are toxic levels of, say, zinc in a soil it makes sense to use plants that can hoover it up into their tissues in order to remove it from the soil. In vegetable gardening we are trying to put nutrients in to the soil. If we get those nutrients from the soil in the first place then we are merely moving them from soil to plant and back again to no obvious purpose. A futher point here is that you generally want to add the elements that your soil is deficient in – but these are exactly the ones that you won’t be able to accumulate from your soil as they aren’t there. These might seem like rather obvious points but it’s not uncommon to see dynamic accumulators recommended as if they are some sort of fertiliser that simply needs to be added to the soil.
Finally, one more problem with the hyperaccumulator model. Most hyperaccumulators are good for just one or two specific elements, but what your plants need is a balance. Things could therefore get very complicated as you try growing a whole range of dynamic accumulators in the attempt to get a balanced nutrient profile. There might not be much room for crop plants. Mike H, on the blog One Thing Leads To Another has put together a list of plants that at least have higher levels of a broad range of plant nutrients in ther leaves than others. Unfortunately it consists entirely of plants – generally considered as weeds – that either very or relatively shallow rooted, meaning that they will only give you back nutrients that were already in the top layer of your soil.
Green manure and nitrogen fixers
The concept makes a little more sense when we consider ways of using plants to move nutrients from places where our crop plants can’t use them to places where they can. One is deep in the soil. The other is the atmosphere.
There is a long tradition in farming and gardening of growing ‘green manures’, plants that are grown not for eating but to be ploughed in to the soil like manure to feed a crop the next year. Most green manure plants are in the legume family as they can do what few other plants can – pull nitrogen directly out of the atmosphere and use it as food. The nitrogen then becomes available to other plants when the green manure dies or gets turned in.
Green manuring is a well established practice and definitely works. It’s possible to use the term ‘dynamic accumulation’ to describe what’s going on as the plants are definitely accumulating a crucial nutrient in an active way, but does the term actually add anything to the established idea of green manuring? I’d suggest that it simply confuses the matter, conflating nitrogen-fixers with hyperaccumulators and deep-rooted plants.
The other place that some plants can access nutrients that others can’t is from the deep soil horizons. I first came across this idea during my forestry degree, reading Forestry Commission research papers (see here, here and here) describing how silver birch improves poor soils by bringing up nutrients from deep soil layers and depositing them through leaf fall on the surface.
However, I also thought I’d have a quick look at a site I often find useful as a check on ‘everyone knows’-type facts: Robert Pavlis’s Garden Myths. Pavlis questions the idea that deep-rooted plants get significant amounts of nutrients from deep in the soil, quoting Robert Kourik as saying that “…. some plants are more efficient at absorbing some nutrients compared to others. Is this due, as many gardeners assume, to deep roots or is it due to more efficient accumulation at surface soils. This remains a grossly unresearched dynamic.”
There are two points here. The first is that absence of evidence is not evidence of absence. The area may indeed be grossly under-researched but that doesn’t mean that we can just dismiss it. I have found plant roots below 1.2m in my garden. They must be doing something down there after all and with herbaceous plants it can’t be about stability. The only explanation I can think of apart from nutrient capture is that they are storing nutrients down below the reach of most things that might eat them, ironically in the reverse of what dynamic accumulators are meant to do! The second point is that deep-rooted plants don’t have to be getting the majority of their nutrients (I doubt if they are) from the deep soil in order to be doing a useful service to the system as a whole.
Dynamic accumulators in practice
So, finally, are dynamic accumulators any use in the forest garden? Let’s break that down in to its three aspects.
First, plants that accumulate particularly high levels of some nutrients in their leaves are of no particular use. They simply take up growing space that would be better used productively.
Second, nitrogen-fixing green-manures are useful, but there is no good reason to call them dynamic accumulators. In the forest garden there is the opportunity to plant perennial green manures that are active the whole season round rather than just the usual annual ones. When I visited Graham Bell’s forest garden in the Borders he was growing Laburnum, one of the few nitrogen fixing trees to flourish in Scotland, for composting material.
Third, deep-rooted plants may well have a role to play in preventing nutrient loss from the system as a whole, but I no longer see much point in planting anything specifically for this property as so many of the crop plants that you can use do it anyway. This has been my experience many times over with the forest garden. I began by planting some plants for crops and others as hoverfly attractors, wildlife plants and ornamentals. As the garden matured and the range of crops expanded I realised that the crop plants were fufilling all these other roles for free. It is the same with deep rooted plants. Crops like sweet cicely, udo, horseradish, monk’s rhubarb and no doubt many more have very deep roots and are useful for harvesting biomass as well as the desired crop. In fact I have come to think of these species as dual-use plants, providing both an edible crop and compost for the hungrier species in the garden.
I do still have a few comfrey plants around, including a clump planted next to my ‘toxics’ compost bin. This bin takes the tattie haulms, brassica roots and any diseased materials. Rather than returning directly them to the soil I just let them break down and be absorbed by the comfrey, which grows at a phenomenal rate and can be cut several times a year. In the future, however, I might replace even this with a crop plant.
I’ve written a few times already about using daylilies but I thought it would be helpful to have one post to tie it all together.
Daylilies have been described as ‘the perfect perennial’, due to their brilliant colours and all round ease of growing. They tolerate both drought and frost and thrive in many different climate zones and soil conditions. They are vigorous perennials that last for many years in a garden and see off most weeds. As if all that wasn’t enough, they are really nice to eat too.
Daylily is not one species but a whole bag of them, all in the genus Hemerocallis. Plants for a Future list over 20 species and only one, H. forrestii, gets anything less than a four-star rating for edibility. Many daylilies that you might encounter do not fit strictly into any one species as they have been hybridised widely and many are listed only as Hemerocallis and their cultivar name.
I should add a few words of caution before I go any further. Daylilies are listed by some sources as poisonous to either humans or pets. Largely this seems to come from confusion with other plants with ‘lily’ in their common name, some of which are not a good idea to eat at all. Many of these plants also look superficially similar to the daylily so obviously you need to be certain that what you are eating is what you think it is (always a good idea in any case). There is a good article by Delishably on the some of the confusion that has arisen here.
All I can say personally is that I have experienced no ill effects from eating moderate amounts of the cooked flowers of Hemerocallis altissima, citrina, dumortieri, exaltata, fulva, lilioasphodelus, middendorfii and minor and a range of hybrids. Bear in mind that any individual can have an adverse reaction to even common food plants and any new food should be taken with some care. Each new species and hybrid is best treated as new rather than assuming that if you are fine with one Hemerocallis you are fine with them all. The only hazard for the genus listed on Plants for a Future is from a single source and states that large quantities of the leaves are said to be hallucinogenic, so you might want to avoid that (or you might want to try it – I don’t want to make any assumptions about my readers).
Daylily flowers are often recommended for salads, which is a bit of a mystery to me as I find them rather unpleasant raw but delicious cooked. The cooked flavour is rich, sweet and complex. The key to bringing out the best in them seems to be frying, which imparts a little bit of a caramelised taste. Perhaps the simplest method is to pan-fry them for about 5 minutes in olive oil. They might have been purposefully designed for stir-frying as their elongated shape is perfect for it. I cut up the largest H. fulva flowers for stir fries but all other kinds just go in whole. One useful property of the flowers is that they will thicken a soup or sauce and I sometimes use them like onion, chopped and lightly fried before adding any other ingredients. There’s a recipe for a miso soup using yellow day lilies (H. lilioasphodelus) here.
The flowers can be used at all stages of their development. Many people consider them to be at their best for frying as flower buds, just on the point of opening. I also enjoy the opened flowers this way and the open flowers of large-flowered species and cultivars are great for cooking as fritters or tempura. If left on the plant in dry weather the flowers will dry up and will then last indefinitely in storage. The bags of ‘golden needles’ or ‘lily flowers’ than you can find in Chinese supermarkets are dried daylilies. They seem to keep their ability to thicken a soup even when dried.
The young leaves of daylilies are edible (but see the cautions above) and I use them in a mixture with others as a pot herb or in leaf sauce. However, they are no better than many more productive plants and harvesting the leaves presumably leads to fewer flowers so I don’t make heavy use of them. They also quite quickly become tougher and more fibrous.
Another part that I don’t use for fear of weakening the plant is the roots, despite one source describing them as ‘quite possibly the best tubers I’ve ever eaten’. I’m sure, however, that if I lived in one of the parts of the world where daylilies really thrive and have become a foragable weed I would be digging them up with enthusiasm.
Growing daylilies is easy. They do best in a moist, fertile soil in sun or semi shade. There is apparently a daylily gall midge (Contarinia quinquenotata) which can lead to distorted flowers. Fortunately I have never seen it in my garden. Slugs are fond of the young growth. This isn’t a problem with established plants but new plants are worth protecting when first planted out.
Choosing a daylily is harder as they have almost become a victim of their own success. Many new varieties are becoming hard to recognise even as daylilies. The trend in breeding seems to be for ever more open flowers, with petals curved back hard – pretty much the opposite of what you want for cooking. Smaller flowers and delicate, divided petals are two more qualities prized by breeders but not by chefs. On the whole, this means that older, more traditional varieties are better for cooking. Varieties I use include Whichford, Burning Daylight, Franz Hals, Yellow Moonlight, Pink Damask and Cream Drop. You can also find double varieties of daylily which have the culinary advantage of being chunkier: H. fulva ‘Kwanso’ is one that I grow. Two common varieties that I have found rather disappointing in terms of size and yield are ‘Stella de Oro’ and ‘Corky’.
In countries where daylilies self-seed I expect there is a tendency to revert to type. If you are lucky enough to live in one of these countries and you find a particularly nice wild specimen I’d encourage you to take it into cultivation and pass it around. It’s a pity that no-one seems to be actively breeding daylilies for their culinary rather than their ornamental properties. I would certainly buy them.
In developing my forest garden, the Plants for a Future online database has been invaluable. It’s my first reference for the edibility, cultivation and propagation details on any new plant. They are now embarking on an ambitious project to extend their database to tropical plants as well as temperate, which I’m sure would make it a great resource for many more people. They aren’t very good at ‘making the ask’, so their appeal for this project currently stands at a fraction of what they need. I’ve just donated £50 and am taking the rare step of sharing their appeal on my blog and Facebook page. Perhaps together we can help them make it happen.
The appeal is at http://www.pfaf.org/user/cmspage.aspx?pageid=187
At the very least I would suggest taking some care about introducing lesser celandine (Ficaria verna) to your garden. Its early growth, glossy leaves, cheery yellow flowers and edible uses all make it attractive, but it has a well-deserved reputation for being invasive in damp or shady areas. In North America, where it is introduced and where several states list it as a noxious invasive speces, the cons almost certainly outweigh the pros. In Europe and North Africa, where it is either native or a long established introduction, the situation is different.
As its Latin name suggests, F. verna is a plant of the spring. It emerges early, flowers early and dies away again before some other plants have even got out of bed – a classic pattern for woodland floor species adapted to making use of spring sunshine before the trees leaf out and hog the lot. Most plants that do this are bulbs – think wild galic, snowdrops and wild hyacinths (bluebells) – and indeed it might be fair to include lesser celandine in the spring bulbs despite its place in the buttercup family, due to the fleshy little tubers that are the key to both its bulb-like lifestyle and its invasiveness.
Incidentally, the shape of these tubers explains lesser celandine’s other common name: pilewort. Their shape was considered to resemble that of haemorrhoids or piles. Under the ancient ‘doctrine of signatures’, God was held to have marked each species to indicate its use to humans, so this resemblance was considered a sure fire sign that celandine would cure piles.
In truth, the doctrine of signatures should probably be placed in the same location as haemmorrhoid cream, but there is no denying the tubers’ use to the plant itself. A handy underground store of nutrients, chock full of toxins, is just the thing needed for an early start to the year. It is also the key to the plant’s persistence, as it is hard to remove all the tubers, and the ease with which it can be accidentally spread around the garden (or the wild). As a result, lesser celandine quickly forms a carpet of growth in favourable conditions.
All this said, there are also reasons why lesser celandine finds it difficult to become a serious pest in any well-managed garden. Despite the seeming ability of the tubers to get everywhere, it doesn’t actually ‘run’, either underground like couch grass or overground like its cousin, creeping buttercup. It’s also a very low growing plant. Its ambition is not to get into the full sun, so it rarely provides serious competition for other plants and it is really quite easy to weed out. It also has an Achilles’ heel, which is that it needs constant moisture to stop the tubers drying out, and it’s never going to be a problem in dry, sunny areas of the garden.
I now let lesser celandine grow in some areas of my garden, where it fills a useful niche as an early spring green – although some caution is required here too! All parts of the plant contain a toxin called protoanemonin, common to the buttercup family. You’ll know if you get protoanemonin in your mouth as it creates an unpleasant burning sensation in the mouth and throat. Fortunately, protoanemonin is easily broken down by heat or drying so it is easy to get rid of.
Different sources seem to have different ideas about the amount of protoanemonin in lesser celandine. Miles Irving, the author of ‘The Forager Handbook’ says “Leaves contain protoanemonin, but in minute quantities. Levels are said to increase as the plant comes into flower, but I have eaten plenty of leaves from flowering plants and come to no harm.” and “Leaves are attractive; the flavour quite mild; good bulking for wild salads containing other, stronger flavours.” Perhaps English celandine is different from Scottish, or perhaps Miles is just more tolerant than I am, but I can’t say that this matches my experience. I only use lesser celandine greens cooked, as a pot herb, an ingredient in leaf sauce, in a stir fry (where they keep their succulent texture) or fried in olive oil until they become crispy. Plants for a Future have an interesting note that the flower buds make a good substitute for capers, but I have yet to try this. Whether or not levels of protoanemonin increase with time, I make most use of it early in the season when there are fewer other leaves around. Miles also says that the tubers have a flavour and texture similar to potatoes and can be use boiled or roasted, but my opinion is that life is too short.
Some variations on the regular lesser celandine are available. There is are varieties that do not produce tubers and are therefore much easier to control. I’m not sure, however, how easy this strain is to get hold of and whether or not it will tend to revert to tuberising as it self-seeds – I suspect so. There is also a handsome bronze variety which looks very striking with the bright yellow flowers against dark purple leaves.
One of the challenges of cooking from the forest garden is using the large amount of leaves, some bland, some quite strongly flavoured, that it produces. Over the years I’ve experimented with various ways of cooking with them, always with the rule that the result must be actively attractive to eat, not merely a way of using up a glut. One of the best is one of the simplest, cooking them together as pot herbs, but I now have a new favourite, leaf sauce!
In short, leaf sauce is a mix of leaves and shoots: steamed, blended and seasoned. Its strength is the opportunity that it gives to blend together lots of different flavours into something very rich and complex. So far the two killer apps I have found for it are pasta and curry, but I’m sure creative chefs could find many more.
The recipe… well, there is no exact recipe. The keys to making it are flexibility and diversity. It can be made at almost any time of year with whatever is at hand and available in the garden. The leaf sauce year begins in February or, in a cold year, March, with the emergence of the wild garlic and other leafy alliums and the start back into growth (in a mild year it hardly stops) of kale, sea beet and leaf celery. Not far behind these are two members of the dock family, herb patience and monk’s rhubarb.
Soon various spring shoots are starting to come up. Lovage, sweet cicely, alexanders, hogweed and ground elder are all excellent used this way. They are all strong-flavoured members of the carrot family that are somewhat milder when the new leaves are just emerging in spring and summer. Hogweed requires a little care in harvesting. Udo and its relatives are similar, and some members of the daisy family also produce tender leaves in spring, notably salsify and scorzonera (Scorzonera hispanica). Young hosta shoots are better used as vegetables but once they unfurl into leaves they can be used in the sauce. Nettles are good to use any time between their emergence and when they start to flower.
The trees also get in on the act. Lime trees in general and small-leaved lime in particular have succulent spring leaves. I’m also trialling toon (Toona sinensis), said to have edible leaves and shoots tasting of onions! Elm leaves aren’t edible, but their seeds are and they are produced in incredible abundance. Climbing up the trees you might find Hablitzia tamnoides, Caucasian climbing spinach.
As we get into summer, the annuals come into play, with more familiar crops such as spinach and mustard. Some crops better known for other parts also have usable leaves, including beetroot, broad beans, peas and radishes, and I’m not even going to try to list all the herbs that can be included.
In autumn, some of the plants that ran to seed and became unpalatable in summer have a second flush of fresh growth, including celery, herb patience and sweet cicely. Nasturtium also starts serious production around this time.
Even in winter there are still abundant ingredients for this dish. The pictures below are from a leaf sauce curry I made in November, with shiitake and oyster mushrooms, apples, broad beans and a vast array of roots, with a sauce from leeks, kale, celery, walking onions, sweet cicely, wasabi (leaves), common mallow and leaf beet.
Recipe (sort of)
- Pick a lot of leaves and shoots. They will boil down a lot and leftover sauce is ideal for freezing, so it’s difficult to pick too many. I usually aim for a carrier bag full. Go for a good mix of types for depth of flavour, with a balance of bland and strongly flavoured ones. This is a bit trial and error and you will find out what you like best over time. For curries I usually go for a greater proportion of strongly flavoured ones and for pasta I add more Mediterranean herbs such as oregano.
- Wash and drain and coarsely chop the leaves.
- Chop and fry an onion. Once the onion goes clear, add garlic and any chopped or ground (not powdered) spices herbs that you like.
- Fry a few minutes more. Add powdered spices, stir and fry very briefly. Throw in the leaves and add a little water so that the bottom of the pan is just covered with water. Sprinkle a little salt over the top if desired and put the lid on.
- Steam the leaves for 15-20 min, topping up the water if the bottom of the pan ever looks like drying out.
- Remove from the heat and liquidise the leaves. I use a small hand-held blender for this.
- Now stir in any other flavourings you like, be it stock powder, curry paste, soy sauce, olive oil or whatever. When making curry I tend to get very eclectic as practically any flavour, if used at a level just below where you start to taste it individually, will add to the depth of flavour.
When it comes to combining the sauce with the rest of a dish, such as the chunky ingredients in a curry, I tend to cook them separately and combine them near the end as finished leaf sauce is thick enough to burn very easily on the hob if not stirred regularly. If you want to cook them together for longer it’s better to water it down a bit to avoid sticking.
Apologies to website subscribers who received a post called ‘Donating’ earlier today. This was meant to go up as a new page rather than being published as a post. The news that I meant to put out today is that my 2016 seed list is now on the website as part of a redesign in which the old ‘shop’ page has been replaced by a new one which takes more of a gift-economy approach. You can read all about it at forest garden seeds.