Eating flower stems

At this time of year, flower stems feature on the forest garden menu in a big way. Flower stems have a number of advantages over other parts of the plant. A mature flower stem may be fibrous and tough, but while growing they are generally soft. They are usually quite chunky compared to other stems, which is handy in preparing them. And compared to the rest of the plant, they are often far less loaded with the defensive chemicals that make plants taste bitter or nasty to us. Finally, removing the flower stems can divert the plant’s resources from seeding and into vegetative growth, which is often what we want from it.

Here, from left to right, are a number of flower stems that I picked for an entirely flower-stem-based dinner recently:

Skirret: chunky, carroty and produced in abundance; best to strip the leaves off.
Radish: leaves, stem and flower heads are all good, not just the root.
Alexanders: less strong tasting than the rest of the plant at this stage.
Mint: minty.
Welsh onion and walking onion: stems becoming a little fibrous but dissolve into a sauce with a lovely sweet onion flavour if cut fine; flowers and bulbils still soft enough to use.
Salsify: abundantly produced, with an artichoke flavour’
Udo – disappearing out of the picture!
Leaf beet: chunky with an earthy, asparagus-like taste.
Celery: the leaf rather than the stem variety, but flower stems are soft enough to use.
Turkish rocket: soft and tasty.

There’s a patience dock in there too, with surprisingly sweet stems, but I can’t see it!

edible flower stems

 

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In Praise of Pruning

Forest gardening draws on the way in which nature itself works for many things, from fertility to pest control. Therefore, when it comes to pruning, you might imagine that it would be best to leave aside such artificial practices and instead let trees and shrubs follow their own natural patterns of development. No-work permaculture at its finest!

This was my own assumption when I started forest gardening, but years of experience have taught me, often the hard way, that the opposite is true. Pruning is a very effective intervention that pays back the effort many times in terms of the accessibility, quality and size of your crops. It is also a great way of learning more about your plants and how they develop. With a little practice, you can use your secateurs as a baton to conduct a symphony of growth, flowering and fruiting in your garden.

I use pruning to achieve three main things. The first is access. The secret to a forest garden in its complex, multi-layered structure. This can also be a hazard as you battle your way through branches and wet foliage to get to your food or get poked in the eye bending down to pick from the ground layer. The main principle here is to prevent plants from branching too low down so that you have a clear view and easy access to the plants growing beneath them. You can also make trees and shrubs more robust and so less likely to be dragged down by the weight of their own fruit.

The second is yield. Pruning is your main method for persuading trees to put more energy into fruiting and less into massive amounts of woody growth. It largely isn’t a matter of cutting off growth after it has happened but instead of cutting back to the right buds so that you encourage the kind of growth that will bear fruit. A tree that is investing less in vertical growth will have more to put into fruit and the lighter, sunnier canopy will generally allow better ripening of the fruit. In a forest garden, there is also a knock-on effect in the lower layers. Many plants naturally produce more foliage than they strictly need for photosynthesis in order to shade out the competition and claim a greater share of the available water and nutrients. Creating a lighter crown gives you more light and productivity in your ground layer.

Finally, there is disease. Pruning is an opportunity to cut out diseases like apple canker and to stop them from spreading. A more open, airy plant is also generally less prone to diseases such as mildew that can attack both plant and fruit. A pruning saw is a double-edged sword though. Carelessly carried out or mis-timed pruning can spread infections or create opportunities for diseases to attack. I generally wipe my pruning tools with meths between trees to avoid transferring diseases.

There are three main principles to bear in mind when pruning. Much of the rest flows from these three. The first is that a bud will produce a shoot pointing in the direction that the bud itself is pointing. On a horizontal branch for instance, a bud on the top of the branch will produce vertical growth, buds on the side will grow out horizontally and ones on the bottom will grow down. The second principle is that growing buds suppress the growth of ones further down the shoot. The practical upshot of this is that you can cut a shoot back to a particular bud and this will be the one that will have the most growth. Leaving the end (or apical) bud will give strong extension of the shoot. The third principle is that plants prefer to fruit on some kinds of growth more than on others. The details vary from plant to plant and the biggest differences in pruning strategy are down to this.

Now, with these principles and a pair of secateurs in hand, let’s have a wander around the garden…

Raspberries
Raspberries (Rubus idaeus) are often grown up wire frames that support the canes and prevent them from being dragged down by the weight of the fruit. The downside of this approach is that canes that wander too far from the frame are usually pruned off, preventing the natural spread of the plants. Over time this tends to lead to the loss of the whole stand to disease.

An alternative approach, which I have now adopted for all my rasps, is to shorten the canes somewhat so that they are robust enough to be free standing. Allowing my plants to wander around the garden has allowed me to make some interesting observations. Raspberries are related to brambles (R. fruticosus agg) and while they don’t share the briar’s trait of making roots at the end of their shoots in order to spread through a wood at terrifying speed, they do share its ultimate dream – of getting up into a tree in order to co-opt its structure and reach the sun. The thorns of bramble and raspberry, like rose, both point backwards from the stem. They are as much about helping the plant to get a grip on the plants that it scrambles over as they are about protection – they are little grappling hooks designed to pull the shoots up into a tree.

Grown in the open, raspberry canes grow with a distinctive kink near the top. When they get near a tree, the purpose of this becomes clear: the canes first punch up vertically through the canopy then loop over, hopefully snaring a branch for support. In the open, I generally prune the canes just below this bend. It doesn’t remove too much stem but it seems to be enough to keep them vertical. Under a suitable tree, I just let them get on with it. The pruning is carried out in winter when the plants are dormant. At the same time I remove the previous year’s canes, take out any weak, spindly, damaged or diseased canes and thin out any areas that are too crowded. The old stems make great kindling; new ones go in the compost.

The exception to this pruning strategy is for autumn-fruiting rasps, which have to be cut right down to the ground at the end of every season and which generally need some support once they are grown up.

Brambles
Brambles or blackberries are like raspberries, except that their shoots are designed to arch over and root at the tip, which makes them something like a cross between creeping buttercup and barbed wire. However, it’s possible to tame a bank of brambles with a little carefully timed pruning. In the middle of summer, when the shoots are growing at their fastest, cut the new stems in half, at the high point of their arc. If you’ve done the same the year before it is easy as you cut them just beyond where they pass the fruiting stems, so it can be done with a hedge trimmer if you have a lot.

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Currants
The currants (Ribes) nicely illustrate the importance of knowing what kind of wood a plant fruits on. Blackcurrants fruit on new growth so they are pruned by cutting the oldest third of the stems down to ground level every winter, giving a constant supply of new shoots.

Redcurrants, whitecurrants, pinkcurrants (all R. rubrum) and gooseberries (R. uva-crispa) all fruit on old wood, so the pruning strategy for them is completely different. Winter pruning is limited to taking out especially old or diseased branches and any shoots that are crossing or growing up from the base. Then, in early summer, all side shoots are cut back to two buds. Because the plants fruit on older growth this doesn’t remove any fruit, but does change the plant’s priorities from making new growth to producing fruit. Leading shoots can be shortened to create a robust, compact plant that will not be dragged down by the weight of the fruit on it.

Overall, the aim with redcurrants and gooseberries is to produce an open, ‘goblet-shaped’ plant that allows air circulation and resists mildew. They are usually grown on a ‘leg’ (the stem of the goblet), a short section of trunk free from any shoots. This is particularly useful when you have ground layer crop that you want to harvest and also helps to discourage gooseberry sawfly, which emerge from the ground every year and have to get up into the plant in order to strip its leaves.

Apples (and pears)
Apples and pears are pruned in the dormant season, between leaf fall and bud burst. The overall aim of pruning is to produce a robust, compact frame of sturdy branches and short fruiting ‘spurs’ that will support the un-naturally large fruits that we have selected the ancestral apple for. Spurs are side shoots that are kept short (just a few buds). As well as ensuring that the apples are borne close to the main stem this encourages the formation of fruiting buds.

The other main aim is to stop the tree putting all its resources into non-fruiting growth. The rule of thumb here is that vertical stems grow rapidly and produce little fruit while horizontal stems grow slowly and produce lots of fruit. As I said above, you don’t want to have to achieve this by cutting off lots of the wrong kind of growth but rather by pruning back to buds that are going in the direction that you want them to in the first place.

Before you start, it’s important to learn to distinguish fruiting buds (which will break to produce a spray of blossom, followed by fruit) from vegetative buds (which will produce a length of stem). In the photo below you can see some spurs pruned back to the large fruiting buds. The vegetative buds on the side of the stems are much smaller. Before you start pruning, check whether your tree is a spur-bearer, with the fruit buds closer to the base of the shoot, or a tip-bearer, with the fruit buds clustered at the end of the shoot. Spur-bearers are more common.

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The first part of the pruning strategy is simple: reduce all vertical shoots to short spurs (or even cut them right back to the branch as they will always tend to want to make vertical growth). The only exception to this is for stems that you want to form the central trunk of the tree in the future. These are generally reduced by about half to keep the tree compact and the stems robust. I generally like to give myself options by keeping a few leading stems at the top of the tree – ones that aren’t needed can be pruned back in the future. Also cut out any diseased wood at this stage.

The second part of the strategy is to create a leading shoot at the end of the branch that will give horizontal growth. Pick a shoot (or two) near the end of the branch and prune it back, by about a third to a half, to a bud on the underside of the shoot. This will grow in the direction it is facing, giving a downward-facing shoot (the tendency of all shoots to curl upwards will translate it into a horizontal one). If all shoots on a branch are trimmed back hard then lots of buds will break, setting you up for a dense tree with lots of vertical growth in the future. The end shoots therefore achieve two aims: they give you a horizontal extension to your branch and they produce chemicals that suppress the growth of the buds further down the branch. The photo below shows the result. Right in the middle you can see a shoot that has been pruned back to a downward facing bud at the start of the year, resulting in a horizontally-growing shoot.

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Finally, the side shoots behind the leading stem are your spurs. Here you can take your pick. Traditonally, spurs were cut back to a short stem of approximately five buds, ending again on a downward facing bud. More recent thinking is to do no more cutting back than is needed to avoid congested and crossing spurs. If the fruit buds are clustered at the tips (a tip bearer), this is definitely the option you need. I’m used to the old way, but will try experimenting with the newer recommendations this year.

Plums and cherries
Avoid pruning stone fruit like plums or cherries in wet weather or in winter as this makes them vulnerable to a disease called peach-leaf curl. A sunny day in July is ideal. Plums do not require a lot of pruning – mostly just cut out any diseased branches and any shoots that are growing vertically or towards the centre of the tree. Summer pruning may involve removing some shoots with developing fruit. Don’t worry about this. Plums always set too much fruit anyway. In fact you might want to thin out the developing fruit at this stage to avoid overcrowding, broken branches and exhausted trees.

Festooning
An alternative to pruning on apples, pears, plums and cherries is festooning – tying down vigorous vertical branches to the hortizontal. This is more work but gives a quick way to achieve a more horizontal structure without removing lots of material and making lots of cuts. I use it, in combination with pruning, on trees that haven’t been pruned for a few years and need some drastic action.

Formative pruning
If you are pruning a newly planted fruit tree, you don’t need to worry about encouraging fruiting as you shouldn’t allow it to fruit anyway in its first year. Instead, this is the time to think about the future structure of the tree. The traditional advice is to cut the leading shoot of a ‘maiden’ (single stemmed) tree at 75cm and then allow the shoots that come from the buds below the cut to develop into the main branches of the tree for a goblet-shaped structure (removing the topmost shoot if it is too dominant). For access to the ground layer, I prefer to have a little more unbranched trunk than this.

Happy pruning!

Winter woes and wonders

It’s been a while since we’ve had a really testing winter in Aberdeen, so in an odd way I am rather enjoying the difficult one we’re having this year – as an opportunity to find out whether more recently acquired plants really are suited to growing in a forest garden in the north. We haven’t had any really deep freezes, but the continual back-and-forth over freezing point that we’ve experienced can be tougher for many plants than straightforward cold.

To start with those that definitely aren’t going to make it, I think I can firmly rule out milk thistle (Silybum marianum) for my garden. It was looking good after December’s frost and snow, but the extended cold seems to have been too much and all four of my plants are now withered husks. I’m also sad to report my mauka (Mirabilis expansa) as missing in action. This Andean root crop is widely described as growing in ‘cold, windy’ conditions at high altitude so it sounded perfect. My plants put on impressive aerial growth in 2016 but produced only small roots. I planted them in various positions around the garden to test out different conditions, but not one of them showed leaf again in 2017.

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Pan breid

Some other plants have been putting on growth but are now looking like they are regretting it. Prime among these is alexanders (Smyrnium olusatrum), a surprisingly hardy plant given its southerly distribution in the wild in Britain. It always starts into growth very early in its second year and never seems to suffer for it. What has been fascinating this year has been the differing trajectories of two different two-year-old plants that flowered and seeded copiously in 2017. One followed this by dropping dead in standard biennial fashion. The other not only clung on to life but sent up a mass of new flowering growth in November and December. This is now being progressively cut back by repeated frosts, but if I had to take a guess I would put my money on it making it through to spring. I’ll be keeping a close eye on this plant to see how far its ambitions for perenniality go.

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alexanders

Another surprisingly hardy plant is globe artichoke (Cynara cardunculus Scolymus Group). When I started growing, received wisdom was that cardoon (Cynara cardunculus Cardoon Group), a variety of artichoke selected for stems rather than flowers, was hardier. That’s all very well, but I’ve never found cardoon worth growing and I’ve never met anyone who actually uses it. Fortunately it seems that globe artichoke is just as hardy after all and mine regularly puts on significant growth in the winter, seemingly unworried by getting cut down by frost every now and again.

Of my newer experiments, I’m glad to see that the Chinese mahogany (Toona sinensis) is looking unaffected by the cold. Not that I’m expecting a mahogany crop any time soon, but the tree’s young leaves have a spicy, oniony flavour that I’m looking forward to experimenting with more. My Ohio spiderwort (Tradescantia ohiensis) has not only been surviving but growing throughout the winter. I’m very keen to try it once spring comes and I’m not worried about weakening it. Creeping dogwood (Cornus canadensis) is not an entirely new experiment. I’ve lost several that I acquired as plants in past winters. This time I grew one from seed. It survived last year’s mild winter and seems to be looking good for this year’s harsher one, so perhaps I’ll get to try its fruit eventually.

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creeping dogwood

The jury is still out on saltbush (Atriplex halimus). I had given up on this species after losing several plants over winter but decided to try again after finding a variety called ‘Cascais’ with larger leaves and shorter internodes – perfect for food production. Winter wet seems to be saltbush’s biggest enemy, so I gave this one a raised position on freely-draining sandy soil and crossed my fingers. So far it has suffered leaf scorch on a number of shoots but there is still a good bit of life in it, so I guess it will depend on what February and March throw at us. One advantage with saltbush is that it roots very easily from cuttings, so I have a backup copy on the kitchen windowsill.

Then we come to the real winter survivors. Land cress is the far easier relative of water cress. It grows throughout the winter and goes perfectly in land cress and potato soup, with the land cress leaves blended into a potato base at the last minute. Leaf celery (Apium graveolens) can be used similarly, and in many other ways besides. I’ll write a separate post about this under-rated vegetable soon. Kale (Brassica oleracea) is another great winter survivor, but I do find that the older perennial kales get the more susceptible they seem to winter cold. This is not only true of Daubenton’s kale but of Pentland Brig, an heirloom variety that has always shown a little bit of a tendency to survive an extra year or two. I’m told that in Florida this variety is genuinely perennial, but some of my three-year-olds are looking a bit touch-and-go this winter.

Salsify (Tragopogon porrofilius) and scorzonera (Scorzonera hispanica), two related root crops that can also be used for leaves and flower shoots, are both lasting well. Salsify is a biennial but it often germinates in autumn and then stands the winter. Perhaps the most unexpected winter survivor is wasabi (Wasabia japonica). Wasabi is possibly a little confused in this climate as it dies down and reappears at odd times, but it never seems too troubled by the cold.

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Variegated Daubenton’s – not a happy plant

I’m not entirely sure whether winters are getting milder or some plants are simply adapting to my garden. When I first grew leaf beet (Beta vulgaris) it generally died back over winter and only re-emerged come spring. This year many plants have been putting on significant winter growth. I must be on something like my eighth generation of self-seeded plants by now so it wouldn’t surprise me if there had been some selection for the conditions in my garden. I was also absolutely astonished to see a living rocket (Eruca sativa) plant. Rocket usually dies back at the first sign of frost. I’d be utterly delighted if it was getting hardier.

While some plants try to tough out the winter, others sensibly die back and wait it out undergound. While some of these won’t be seen again until May or June, others are more adventurous and quite a number are appearing already. Leading the charge is the onion family, including the chives (Allium schoenoprasum), Siberian chives (A. nutans), prairie onion (A. cernuum), German garlic (A. senescens), welsh onion (A. fistulosum), Sikkim onion (A. sikkimense), wild garlic (A. ursinum) and tree onion (A. x proliferum). They looked like they were regretting their rashness a little last week as blizzards swirled around them, but this is pretty normal behaviour for onions and I don’t think any of them will come to any harm from it. Only the three-cornered leek (A. triquetrum), which grew all through last year’s very mild winter, is looking decidedly unwell – perhaps not surprising for a plant more at home in the Canary Islands.

Then there’s the allium that laughs at winters, the queen of the Scottish vegetable garden, the leek (A. ampeloprasum). I have a range of perennial leeks, including elephant garlic, Babington leek and wild leek ‘Chesil Beach’ (which puts the song ‘Echo Beach’ by Martha and the Muffins into my head each and every time I see it), but perenniality is never far from the surface with leeks and many lines of cultivated, biennial leek occasionally form overwintering bulbs. This seems to me to be a promising route to new perennial varieties. For biennial leeks, I’ve tried many new varieties but nothing seems to beat the traditional ‘Musselburgh’ for winter hardiness and growth.

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Wild leek ‘Chesil Beach’. Far away in time.

Other plants already showing a bit of growth include the sour-leaved garden sorrel (Rumex acetosa) and a very handsome bronze lesser celandine (Ficaria verna). There are even some mushrooms! Jelly ear (Auricularia auricula-judae) and oyster mushroom (Pleurotus ostreatus) both seem to be unconcerned by winter cold.

With some other plants there’s nothing I can do but wait a little longer to see if they re-emerge from underground hiding this year. One of those that I’ll be most interested in is myoga or Japanese ginger (Zingiber mioga). This survived last winter but failed to produce any of the flowers which are its only edible part. If it makes it this time I’ve promised it a move to a sunnier position.

Finally, I’ll share with you the ingredients of last night’s curry, sourced almost entirely from the forest garden, to show that there’s never a time when you can’t get some sort of meal from it. Harvested that day: leek, potatoes, yacon, celery, salsify, hopniss (Apios americana), sweet cicely roots and leaves, jelly ears, leaf beet, kale, wasabi and alexanders. From stores: oca, beans, neep and apple.

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lesser celandine

Seed list 2017

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.

Are ‘dynamic accumulators’ a thing?

‘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.

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Nettles are high in nitrogen, sulphur and magnesium

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.

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.

Laburnum

Laburnum

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.

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comfrey-triffid

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bee enjoying the comfrey flowers

Eating daylilies (Hemerocallis)

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.

Plants for a Future appeal

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

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