Thursday 28 September 2017

RHS honey fungus hunt

Armillaria, honey fungus or bootlace fungus - they all mean the same, but very importantly come in different kinds

Armillari mellea
My previous post about this much feared disease suggested that finding it in your garden is not the disaster it is cracked up to be.
When I received an email from the RHS announcing their fungus hunt I took the opportunity to wing back a link to my my rather complacent post.
The very next day I received a long reply from RHS researcher Jassy Drakulic. The kind of things that I was saying were exactly what she would like to know. The RHS are fully aware about all the damage that the bootlace fungus can do. Members send them their problems! Members don’t usually bother to tell them when no harm has been done. They are now inviting the general public to report their experiences.

The RHS would like to know
Have you honey fungus in your garden?
If so what damage has it done and to what?
Equally important what plants remain healthy?
Have you found bootlaces and yet no or little damage at all?
Do you have pictures of armillaria mushrooms - they need to identify which kind you have got.
Have you historic experience of honey fungus in your garden or elsewhere?
Do you have strange mushrooms growing on living or dead trees or in the ground that you suspect to be honey fungus?

Tell the RHS your story. The link at the bottom will take you to the details of their internet hunt. They ask for quite some detail but don’t be put off and if you provide very little information it is better than none. I wasted ten minutes trying to find the link to find the right form! Silly me - just press the link  ‘complete survey’ under the picture of the mushrooms!
Although Jassy might contact you about further details please don’t expect any identification service. You need to be a RHS member and go down a different route for actual advice!

Why don’t RHS get a complete picture?
Apart for the obvious that people only send in their problems there might be several reasons

1. Gardeners fail to recognise a plant death is due to honey fungus
2. Certain plant deaths get noticed! A dead tree or a hole in a hedge is pretty obvious and might lead to disproportionate  reporting.
3. The obverse of point 2 is gardeners do not expect bulbs or herbaceous plants to be killed - but they can be.
What on earth is happening to my evening primrose?
4. Some plants are disproportionately reported when the real cause of death is susceptibility to such as drought, poor drainage or winter cold  and the bootlaces join the party later

Don’t panic
My opinion is still that honey fungus is excessively feared as the kiss of death to a garden and that gardeners go to exorbitant lengths when evidence of bootlaces are found.
Jassy took me to task with some of the details in my previous post and I reproduce part of her e-mail to me here.

Hi Roger,

Thank you for your e-mail! I’m trying to gather as much information about how Honey Fungus affects gardeners as I can and case studies like those you’ve described are really valuable to me to get a better perspective of the reality of the disease impact and how people interpret the science based on what information is out there.

From the look of those mushrooms they are sulfur tuft (Hypholoma fasciculare) not HF as the spores are dark not pale and there is no annulus. The bootlaces are HF however, and given the abundance of them along with how few plant deaths your garden has had, it is likely to be colonised by Armillaria gallica. This HF species is not a true pathogen at all but only an opportunist that can kill once its host plant is weakened in some other way (pests, mechanical damage, drought - rather than waterlogging).

The point that is made in the blog post is the very reason for this year’s Honey Fungus Hunt! Our last survey (2004-7) was based on samples received at the RHS, which itself limited the dataset to only times when host plants had died, so understandably we got lots of incidences of the most pathogenic species in gardens – A. mellea. By asking the public to record any mushrooms they see, which plants they’re found with and how healthy those plants are I can get a better picture of how often HF occurs without causing plant death as well as gathering any historical information about HF in their gardens that they wish to share. (
The survey will also help gardeners ID HF for themselves better – with such resources available the person ID’ing your mushrooms would have been able to tell that it wasn’t right because of the spore colour, for instance (

The two links in the email are very useful

Recognition of bootlaces
Bootlaces - not roots
Bootlace - and roots
Jassy tells me that if in doubt between roots and bootlaces  if you laterally tear a suspected bootlace you get a very strong fungus smell

Not sure about this. The white specks are fungus mycelium - looks like mycorrhiza?
I suggested in my previous post that it is something of a lottery whether your honey fungus is a curse or a damp squib. I noted that if you hit the jackpot and had a susceptible plant that is old and growing in predisposing conditions you might be in trouble. I today add a fourth variable to consider - whether you have a benign or aggressive species or strain of the fungus.
Jassy in her e-mail made the fascinating point that a less aggressive species such as Armillaria gallica might be antagonistic to the more serious effects of the feared Armillaria mellea.

Some more examples of my own confusion

1. My Spartium junceum, Spanish broom, was checked and lost its youthful vigour after record cold Winter 2010. It's never been the same. It lost its main frame trunk but a strong shoot from the ground took over and made a 'passable plant'. It is in the area that I previously reported honey fungus and for this post I recently scrabbled around.

Stump several years dead and still surviving trunk 
Today, October 2017. The top is still nice - and I hope the plant is recovering

What have I got?

Former misidentification of honey fungus - picture previously  taken near my spartium
2015 picture of original tree stump two metres away from spartium
2. When walking through a near village I spotted thirty or so fungal fructifications emerging from a manicured lawn under a dozen or so healthy mature specimen birches. My own identification skills are such as that I would not be sure of a common mushroom. I did not have opportunity to examine more closely. Most such fungi are completely harmless. Do not fear to submit to the survey if you are not sure.

Perhaps someone can tell me. I dare not go closer

3. In my previous honey fungus post I pictured a somewhat distressed lilac growing in my 'infected 'zone'. It ticked the right boxes. When we moved in fifteen years ago we had pruned it down from an overgrown thicket which had had several trunks.We had also chopped down half dozen old Leylands and being me I had left stumps in the ground! The site is very dry in Summer. As I say all the right boxes, hard pruning, potential source of infection, summer drought, old plant and a susceptible species (nineteenth on the previous RHS survey).
Worse I have allowed my ivy to grow over it - always a symptom (and cause) of a weak growing plant. For ten years now Brenda has told me its on the way out and I should remove it. Every year it flowers magnificently.

From my post three years ago
I really must prune out some ivy
A young sucker is ready to replace the old lilac
I was very cavalier about leaving tree stumps in the ground in this old post. The only amendment I would make to my advice is that I failed to emphasise to cut your tree trunk close to the ground. This is not relevant to honey fungus - or is it with a greater dying food source? - it is forgetting it is there and tripping over!

My original post on honey fungus

Thursday 21 September 2017

Are fertilisers a good thing?

My giant borders neither need or receive fertiliser. Were they to need extra nutrients I would have no hesitation to apply a top dressing of general fertiliser

I am tempted to say  fertilisers are ’the best thing since sliced bread’ but then I reflect that much bread today is not very nutritious. I might even say ‘junk food’. But then many gardeners think that fertiliser is junk food and sometimes it can be! Bonemeal anyone?

I have written about fertilisers many times before. I don’t like to repeat myself - although regular readers might not think so. I cannot completely avoid it when new readers have not yet heard  my ramblings. I have passed on most of what I know and worse, have used up my best ‘jokes’ and stories. Today I will limit my attempts to guide you to the more practical aspects of fertiliser use in the links below. (I don’t want to lose you by sending you into the ether too early) There are a lot of links today which I hope will serve as a reference. For example, I explain that when I talk about fertilisers I mean ‘concentrated sources of nutrient’ and not bulky manure. Bonemeal does not qualify as either.

Not only do my borders usually not receive fertiliser I do not import bulky manure  

Growmore is a far superior general fertiliser to bonemeal
The thrust of my item today is to question how much gardeners need to use fertiliser. Scientist Peter Williams has no doubt of their value and neither do I. If your plants have insufficient nutrients they will fail to achieve their genetic potential. This might include anything from size, speed of development, health and disease resistance, flower and fruit size, colour, absence of deficiencies and plenty of flavour. Neither of us have any inhibitions about using them when they will enhance the beauty of our gardens or the taste, health or yield of our crops.
That is not to say fertilisers are always necessary. Indeed in many cases there is no need to use them at all. Many garden soils are highly fertile; gardeners use manure and compost and good gardeners generally recycle soil organic matter and nutrients. Our soil can be a rich source of fertility. Why add more?

No need for fertiliser here
I have written before that my three naturalistic gardens have never had fertiliser. Neither does Cathi’s grass verge - indeed her complete garden -  nor my project in Lyndi’s field or in most of my own flower borders. Never-the-less in a year I almost get through a complete 25kg bag of yaramila fertiliser. Further on I will explain how.

No fertiliser for Cathi's new grass feature (although I am  pleased that her soil is naturally fertile)
Many gardeners seem to regard it as as a sacred duty to supply fertiliser in their planting hole (or less damaging adjacent to it). Sometimes this might be a good thing but usually there is a greater need to get the plant established and perhaps apply a top dressing of fertiliser later. Fortunately many amateur fertilisers - but by no means all - are mere toys and like bonemeal will do little harm (bonemeal will do no good either). 

Objections to fertilisers discussed
This is the real thrust of my article today

Do they damage soil structure?
In the round this is nonsense. However in the big wide world there are thousands of soils of different nature and hundreds of so called fertilisers. Many are of dubious nature and some growers excessively apply them. There are bound to be instances where there will be an adverse reaction between between chemical and soil. Ammunition for the anti fertiliser lobby!
More usually fertilisers are neutral in effects on a soil’s physical condition. A few such as lime and calcium sulphate are applied to directly improve it.
A secondary effect of using fertiliser is that increased growth means more biomass is available to the gardener and farmer. When decayed organic matter is recycled there is improvement to soil structure. I previously wrote about how use of fertiliser contributed to the greening of Yorkshire’s pit heaps and creating ‘new soil’.
I have also written how my former allotment which never received imported organics over the years, that with sparing use of inorganic fertiliser, recycling of organic matter generated on site and a no dig policy, that it became black with organic matter.

What gives credence to the myth that fertilisers are bad for the soil structure is the way some farmers abuse them to maintain high yields and neglect other aspects of good soil management. (‘Good soil management’ might be as simple as minimum cultivation).
Claims of bad soil management is often true. I hope it does not apply to you.

They pollute water courses, ground water, lakes and the sea
This is a problem when farmers use large quantities, apply near water courses and apply them when leaching conditions prevail - usually in late Winter.
The main problem is soluble nitrate which arises from ammonium and other soluble nitrogen-containing fertilisers.The problem is more or less restricted to misuse of these ‘nitrates’ and from agriculture the problem is significant. 
Phosphates pollute water too and significantly so. Fortunately virtually all phosphate applied by growers is strongly absorbed by the soil and other than being hugely significant in contributing to the health and nutritional value in crops never leaves the ground. Phosphate pollution by farmers and gardeners only occurs when the nutrient directly bypasses the soil. Hang your head in shame if your compost heap made on hard standing leaches out direct to a drain! (In limited but sometimes significant cases phosphate can directly enter the water by wind blown soil erosion)
The main source of phosphate pollution is when phosphate rich detergents from your washing machine empties to your drain.

Organic gardeners should not be complacent about water pollution. Their organic manures release copious nitrate too

The amounts of fertilisers used by gardeners are minute compared to those used by farmers. I would suggest that gardeners less commonly apply them to not-yet-sown soil than do farmers and rarely as early as February - a time when leaching is most likely. Gardeners certainly don’t use great machines that fling fertilisers a long way. (My own garden gets a boost when the farmer fertilises his field).
Leaching under most growing conditions barely exists in Spring and Summer. Heavy rain washes nitrogen just a little deeper and hungry roots find it.
In my view a responsible gardener should have no reservations about his fertilser causing pollution.

Fertilisers are very energy intensive and add greenhouse gases to the atmosphere
There is no doubt that agriculture is energy intensive and uses a lot of fertiliser and diesel. In addition to carbon dioxide production, the greenhouse gases such a nitrogen oxides  - and methane from cattle - are also an issue.

My hard yaramila prill stores very well and a 25kg bag satisfies most of my annual fertiliser needs. (Lots of little bags of 'specialist' fertilisers is wasteful folly)
I wondered about the energy used in my own annual usage of 25kg of yaramila. In a very much ‘back of the envelope’ estimation I calculate that the manufacture and distribution of my 25kg bag produces the same amount of carbon dioxide as when 15 litres of petrol burns in my car. Interestingly the monetary cost of each is almost exactly the same.

Fertiliser might scorch my crops and cause ‘soft’ disease-susceptible growth
Unskilled and heavy use of fertiliser can damage plants.This is perhaps why weak toy fertilisers are often sold and recommended to amateurs. Not that misdirected chicken droppings will do no harm or that inferior lawn fertiliser spreaders cannot lead to disaster.
Some gardeners excessively use single nutrient fertilisers which are not balanced. High nitrogen alone especially if delivered in poorly illuminated greenhouse conditions does create soft and disease prone plants,
Nurserymen tend to use high levels of nutrients to achieve more speedy production of their plants. My all time least popular post is about ‘soft growth’ (there seems to be a negative correlation between my effort and a post’s popularity). I still wonder why when I buy a new dicentra at the garden centre it almost inevitably dies….
Sensible use of fertiliser grows better plants. This does not always happen.

Excessive phosphate application
Superphosphate was the first major manufactured fertiliser nearly two centuries ago. It increased yield and transformed farming. Phosphate is an essential nutrient. 
It is not a bad thing that it accumulates in the soil but there are circumstances where there can be too much. Most gardeners and farmers needlessly apply more to their soils. Unfortunately most general fertilisers include more phosphate than is needed. It’s not usually a problem, more a waste of resources.
Gardeners sometime find excess phosphate a problem when they attempt to naturalise wild flowers in grass. It is not that wild flowers do not like it, it’s just that nettles and coarse grasses like it better.

Effects on soil micro - organisms
In the rich cycle of organic life in garden soil numbers and composition of bacterial populations vary by orders of magnitude within just a few days of changing conditions such as warm, wet or dry. As long as we manage our soil well such changes do not matter a jot to our gardening. Fertilisers might do all of stimulate bacterial action, have no effect what-so-ever or inconsequential inhibition.

Inhibition of mycorrhizal fungi is a more serious concern. Fertilisers seem to break the faustian mutualistic contract between soil fungus and plant. If the plants’ need for nutrients is easily satisfied by a fertile soil - however this is achieved - then there is no need for the plant to donate to the fungus its carbohydrate resources and ergo less mycorrhiza.
In the wild mycorrhizal associations abound. For some plants they are essential for survival. Fear not, there are more mycorrhizal associations in your garden than you think - even when you use fertilisers.

So how do I get through 25kg of YaraMila in a year?

Buy this analysis for general use. Your local supplier might sell suitable similar products. Not usually sold at garden centres.
Other than iron sulphate on my lawn, yaramila is the only  fertiliser I use.

My pot grown tomatoes need generous applications
1. In my vegetable garden I might lightly scatter perhaps 30gm per square metre over any area I plant or sow. This may be before or after plant establishment and if I remember. Overwintered brassicas might get a little extra in Spring

2. On my sandy soil I find that top dressing my soft fruits such as blackcurrants, blackberries and especially raspberries works very well. My asparagus too. In recent years I have found that very early application in late February is best!

I top dress my contorted robinia three times a year
3. We have a large number of plants in display containers growing in soil. Nutrients do leach from containers and plants have a much smaller root zone than in the ground. Some of our tubs itinerate between indoors and outside. These might receive a top dressing as often as four times a year - as well as having been ‘made up’ with fertiliser content. This nutrient need would be greater if my plants were growing in regular potting compost.

Although I apply yaramila to my tubs of agapanthus I never need to fertilise those in the ground
4. I make up my own seed and potting composts from my own sandy soil. Most garden soils are unsuitable for this practice - but I think many gardeners do miss an opportunity. I sometimes add small amounts of yaramila. More sensible folk might use a slow release fertiliser.

5. I don’t liquid feed. I do not disprove of liquid fertilisers it is just that I am lazy (and mean) and top dress with fertiliser instead. All our pot plants have a scattering at some time or other. Even the orchid collection with a dozen granules or so per pot. They love it

6. A typical gardener might annually apply lawn fertiliser at say 20gm per square metre to their lawn. I have perhaps 600 square metres of lawn and grass paths embracing my borders.
I prefer to not box off my mowings and consequently return nutrients when I 'mulch mow'. Perhaps every other year an area of grass will receive a little fertiliser. Perhaps about 20gm yaramila per square metre. If a little goes on my borders when I fling it so much the better.
To apply this rate to the whole of my lawn would take 12kg of yaramila - half a bag!
In different circumstances Peter Williams applies 20gm/sq m of yaramila three times a year to his lawn - including midwinter!

This amount of homemade charcoal will be 'charged' with about 1kg of yaramila over the next year before I use it
7. Readers will know my penchant for making my own biochar when I douse the embers of all my garden fires with water. This wonderful medium initially is powerfully absorptive of nutrients and needs charging. If I have fertiliser handy when I pass my maturing pile it gets some.....

To buy yaramila you will need to find your local horticultural trade supplier or more easily order on the net

These links provide more detail

Why you do not need to buy lots of little bags of specialist fertiliser. 
My thing against bonemeal
All year round use of fertiliser
Why general fertiliser is suitable for your lawn
My penchant for using charcoal
Restoration of a slag heap 
Buying professional fertiliser
Crushed rock myth
Do fertilisers degrade soil? - whoops I have been repeating myself
My homemade soil potting compost
My post about hard and soft growth was a damp squib

This vigorous plant finds its own nutrient
So do these delicate ones
 Delphiniums need a little help on my very sandy soil
The annuals are rather lush on my former vegetable garden

Saturday 9 September 2017

Elimination of nettles and ground elder: victory declared

Ground elder almost gone in just over two years
(scroll down to find nettles)
 Just demonstrating using pure water!
I am standing on ground that 28 months ago was solid ground elder
For some peculiar reason my original post under a similar title has been read 40,000 times. It would seem that many gardeners have trouble with these weeds! My original project spawned a continuing series of posts about Cathi’s grass verge and this will serve as a weedy update for those of you who have skipped the details of developing this garden feature.

This looked like the picture below 16 months ago
Note the sneaky self seeded nettles too
As to nettles I claimed victory before the end of the first season. The strong stands of nettles were completely killed by the first two or three applications of glyphosate and/or MCPA. (MCPA  bought as Agritox is particularly effective against nettles)
As I explained at the time nettles will always be with us as new ones develop from seed and join the pantheon of weeds from seed that will always need repeated attention. Even now In my own garden I often spot a nettle that has sneakily infiltrated a tall plant. It gets immediate attention with whatever tool I have in my hand be it border spade, fork, trowel or secateurs. I even enrol my hankie to pull it or for small ones more bravely use my bare hand. I even slide in with my boot. 
It will have seeded  from an earlier intruder I have missed!

A week before Open Day and I spot this
I hold no truck for those foolish people who grow nettles on purpose in the misguided and largely discredited belief that they provide unique habitat for rare butterflies and moths. When did you last see any caterpillars on your nettles?
For that matter when did you notice a shortage of nettles? I just cannot believe anyone should want to grow them. 
In another context growers of wild flowers denude their soil to reduce the vigour and discourage weeds such as nasty nettles. The only good thing about having nettles is when they take over a garden it does indicate high fertility!

Ten years ago I replaced the farmer's verge of nettles with helianthus so loved by the bees
My claim for eliminating ground elder is bit of a cheat in that the two year period in which I claim to have slayed it includes several months of its third Summer season of growth and even now some are still there. I make my claim that although by Summer 2017 some remain it is no extra inconvenience to my routine and very speedy weed control. Other than myself no one sees any there. It is weak and sparse and easily targeted. 

The problem of ground elder

I have previously stated that it is one of gardeners’ worse weeds.This is a little unfair as it is not particularly unattractive and does not stand out as a weed. Introduced by the Romans it is edible ground cover. A dear lady who managed a cemetery garden in Bath put a label on it and it was generally admired. As a complete ground cover it does the job very well especially if mown or strimmed after flowering -
even under shrubs…..

The variegated form looks rather nice
As my articles illustrate it takes a few years to get rid of ground elder by repeated spraying but it eventually goes. The real problem is when gardeners try to chop it out. The fine long lived roots are very insidious and intimately infiltrate between the roots of perennial plants and traditional cultivations spread it all over. Innocent gardeners donate infested herbaceous perennials to friends and bingo they have a new weed. They only start to notice when the ground elder starts to take over. and then it’s too late.
The reasons not to chop it are even more subtle than I have already suggested. I have explained that if it has been cut into small pieces and gardeners have failed to pull it all out - as they inevitably do - that chopped pieces rejuvenate erratically and new and for spraying necessarily well developed leaves cannot easily be treated. In this unhappy situation you need to leave it alone for several months of its growing season before you can spray it. When I was a weed control trouble shooter my easiest clients who needed elimination of such as couch grass were those who'd given up completely and intact weed abounded. Couch was nearly all eliminated after my very first spray. For those who had faffed around it took very much longer.
No the real problem is the distribution of small pieces of root. Any new plantings over the first three years might meet severed ground elder roots and be intimately infiltrated. A year or two later the herbaceous clump is more weed than plant. (It is much easier to control under shrubs)

It regenerates in almost exactly the same place
A key thing that has now only belatedly dawned on me is that the intact sprayed ground elder clumps not only still receive translocated herbicide even when some leaves have been missed but that more significantly repeatedly regenerating new shoots appear in more or less the same place. (At first there might be little terminal extension). This knowledge is what has enabled me to plant between groupings of ground elder in as early as the second year and Cathi’s verge was beautiful with Autumn planted Spring bulbs in that very first new season.  
In Cathi’s border it has been very easy to spray the very obvious ground elder.(As well as the rest of the weeds that come from seed). Even where some are actually under her plants, still intact they are easily targeted with an accurate squirt.

More tricky to spray but easy with a body contortion and a low pressure directed squirt
I end with a small confession. I have claimed that I completely eliminated all the strong two foot high monoculture of ground elder that completely covered the third of an acre village plot ten years ago. For all practical purposes it was gone by the third year. (In the second and third year it had been temporarily clothed with expendable annual flowers).
In truth a few ground elders had been missed. As my routine weed control is knapsack spraying it has not mattered a jot. Even now I occasionally find one - even two or three - small and subtly hiding, When spotted I spray it - as I do routinely for seeded weeds.
There is absolutely zero ground elder in my own garden! 

Fortunately ground elder does not come back from seed!

More about nettles

I fear I might have been little coy about eliminating nettles. Because it is so easy for me to get rid of them with MCPA (Commercial source Agritox) and given an initial clear run free of garden plants in both Cathi’s verge and Lyndi’s field very sturdy nettles were completely eliminated with two or three sprays over four months in the first season. (Remember for MCPA which is also a constituent in many amateur lawn weedkillers a ’clear run’ includes nettles growing in a grass field)

This neglects nettles’ ability to freshly and rapidly reassert themselves from seed. Although all the nettles were completely killed in my other project in Lyndi’s field, now in the second year you will still find some! I go to spray in Summer once a month. In a quarter of an acre it is very easy to miss some small seeded nettles and in such a large area it is easy to miss a few on my next visit too! It might be after ten weeks when I find luxuriant clumps. (her old paddock is very fertile after all those horses). By then the nettles are almost seeding! Worse my regular spray is glyphosate which against nettles is not as effective as MCPA. (Please don’t embarrass me by asking whether you can legally mix glyphosate and MCPA together).

I shall just keep pegging away until the nettle seed is out of the system. Most will very soon be gone as I practice zero cultivation and I do not bring buried weed seed to the surface. But you never get rid of them all. Overall the project is going very well.

How effective is glyphosate against nettles?
Undoubtedly sprayed at the right rate and frequency it will eventually kill them but I am in denial as to how ineffective routine glyphosate spraying can be!

I remember when I was hired to manage an old walled  kitchen garden free of established perennial weed but that by neglect of the necessity to prevent weeds seeding for in this case the last hundred years the soil weed seed population was phenomenal. Poor Paul  - who I taught to spray out the regular crop of emerging weed seed. He was concerned that annual nettles were persisting. What should he do? …. (Annual nettle Urtica urens is distinct from the more common perennial kind).

When I was writing my original post on nettles and was checking out a few things on the net I found some references to folk routinely spraying rough weedy areas with glyphosate and claiming that it seemed to encourage nettles! Clearly their spray was not strong or frequent enough and killing competing vegetation gave nettles a free run. I wondered if the victims were rich enough to be foolishly using amateur ‘ready to use spray’. 
I don’t actually know how strong these ready made solutions actually are. I imagine very weak!

I thought I should find out what strength of glyphosate is responsibly recommended to kill nettles. The net is very opaque when we home  gardeners seek information as to how to use professional glyphosate in our garden and I found no references suggesting nettles might be ‘difficult’. It is ironic that when searching google for recommended dilutions for nettles I found Roger Brook at the top of page two.

My previous experience suggests that 1 in 50 dilution of 360g/l commercial product is sufficient. But what if in my haste I fail to achieve complete cover (but as ever best short of wasteful ‘run off) or if a complacent gardener sprays regeneration too late? (or even too soon!)
I think if I wanted to be sure to get rid of it now I would use dilution 1 in 40 which I would make up with 250 mili-litres of product dissolved in ten litres of water in my 15 litre sprayer. (A full sprayer is too heavy for me)

A problem with MCPA
You might conclude that if you have nettles in a paddock, on waste land or under hedges and trees you might prefer MCPA. I went to the Agritox website to read about dilutions and to my amazement I found the weasel words ‘not approved’ for knapsack sprayers’. What on earth does ‘not approved’ mean? There are many things in this world that I disapprove of and they still carry on. Why should MCPA be plastered over tens of thousands of acres of grassland and cereal crops with huge tractor mounted monsters and applied in amateur products to almost everyone’s lawns and yet knapsacks, those most accurate of all sprayers be not approved for applying MCPA?
If these things bother you the sister professional product  24D is ‘approved’ for knapsack spraying. Virtually identical to MCPA and used as alternatives or mixed together they have been used for selective weed control in cereals, grassland and lawns for the last fifty years. 24D bought as similarly priced Depitox kills nettles very well.
It amuses me to think that when I ordered some 24D thirty years ago my supplier substituted MCPA as if it were identical and I have used Agritox in my knapsack sprayer ever since.
A new nettle project

Although I look after Cathi’s garden I have not been concerned with the strong clumps of nettles in her fields where her fifteen soay sheep and her two rheas graze. I am about to start a demonstration in a one acre field

Spike hates the nettles
This Spring Cathi had her nettles ‘professionally’ spot sprayed. Unfortunately the usual story, they were not sprayed again. By now the old nettles have completely regenerated and new young plants have come from seed. It is normally necessary to respray at least on one further occasion perhaps about ten weeks later. This is when new strong growth has occurred and before it can consolidate and recover or new nettle seedlings get going.
The pictures below represent a necessarily new start.

Sprayed five months ago and look what happened!
On the roadside of the fence I have now sprayed with 1 in 50 glyphosate. In the fields I used 1 in 75 MCPA made up by dissolving 150 ml in ten litres of water 
Typical patchy distribution of nettles. Perhaps the ministry would have Cathi hire a tractor?
She might use a watering can or a hand sprayer but a carefully directed knapsack is ideal. Perhaps the ministry would prefer Cathi to use an amateur lawn weedkiller or would that be illegal?
I intend to completely eliminate the nettles in one of her fields. I will update this post to show how things proceed and I will take care not to exceed Ministry regulations that dictate maximum doses per unit area per year.
It took me twenty minutes to spray the nettles with a 1 in 75 dilution.

Watch this space!

Links to related posts

My original post on nettles and ground elder project
Prologue to second year of project
Report on first year

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