Sunday 31 January 2016

Every picture tells a story

Bolton Percy circa 1980

It’s thirty five years since Bolton Percy churchyard was first opened as a garden under the yellow book Open Garden Scheme. That year the variegated honesty was absolutely magnificent and plants I had potted for sale walked off the stall. Every year since the honesty has returned but has  never been quite so magnificent as that year when I took the above picture as an acetate slide.

A copy of which hangs on our wall together with three other cemetery pictures all of which are professional! I used to trade press interviews for slides for my lectures. If I can secure permission to reproduce them there will be three more stories! Today’s picture is my own and must have been shown in my public lectures at least two hundred times. I have had plenty of practice in telling tales about it!

I wrote about variegated honesty in my post about biennials. The post is long and rambling and very few read it so I will tell you about Lunaria biennis variegata again!
Its a very interesting plant which has the potential to germinate at almost any time of the year if conditions are suitable. A peculiar feature is that if it germinates in none frosty conditions in its first year it grows green without variegation. This is the best way to grow it when it germinates in June, makes a strong first year plant as biennials are supposed to do and then the following Spring it flowers magnificently just like the picture. After the Winter’s cold it flowers with the most wonderful variegation.

On the other hand if it germinates in cold it is immediately variegated, flowers insipidly and is thoroughly confused....

My variegated honesty has been re-seeding itself for the last 35 years. Sometime I help it and scatter it around . I remember one year I spread it over a thin ground cover of ivy and to my surprise it grew through it and almost suppressed it. I got lucky that year!

Geranium macrorrhizum is a strong growing herbaceous perennial ground cover which is much used in both my cemetery gardens. It is the perfect plant to illustrate the principal that if you eliminate all perennial weed vegetative propagules and make sure they are dead then once the ground cover is established you never need weed it again. The leaves go attractive colours in Winter but maintain sufficient cover to suppress any weed seed germination. 

Conversely it is a nightmare if planted into existing couch grass, ground elder or bindweed!

In my lectures I would draw attention to the vulgar combination of orange Euphorbia griffithii and pink geranium.
There is another interesting combination of the drought tolerant thug, Euphorbia robbiae and the yellow bog Iris.

These things happen when you don’t have a plan.

Sunday 24 January 2016

Fertilisers degrade your soil; myth!

I makes my blood boil when I read that using  fertilisers will damage the structure of my soil. 

I will accept the more vague notion that misuse of fertilisers might damage soil. 

I concede further that some gardeners so misuse fertilisers that damage to their plants is almost inevitable.

I must define fertilisers so we can agree on our subject. Fertilisers are concentrated sources of plant nutrients. So defined they do not include manures, compost or other bulky organic matter. Fertilisers may by organic or inorganic. Bonemeal and dried blood are organic, superphosphate and growmore are inorganic and might be dubbed ‘chemical’.
Because many different chemicals masquerade as fertilisers I may have to qualify some of my judgements today!
Growmore is a general purpose NPK inorganic fertiliser suitable for amateurs

‘Fish, blood and bone’ is an organic general fertiliser albeit it’s potassium is usually made up with inorganic potassium sulphate.

The boundary between manure and fertiliser is sometimes quite close. I would regard this rich nutrient liqueur from a worm bin as a fertiliser on account of its high concentration. In a similar vein chicken ‘manure’ is best regarded as a fertiliser.

The myth of fertilisers causing soil degradation I think arises because there is a very long history of farmers and growers relying on fertilisers to maintain high yields and over the years neglecting sound soil management practices. Excessive cultivation, soil compaction, failure to recycle natural organic matter all may be cited as evidence. Such practices undoubtedly do lead to loss of good structure.
That in no way means that when I scatter Yaramila on my undug vegetable garden it will damage my soil in any way at all.

Indeed I would argue that use of fertilisers can improve soil structure and otherwise benefit the soil. A plant short of nutrients and in particular nitrogen, will not grow very well. It will make less bulk. There will be less organic matter created than if fertiliser is given. Such organic matter responsibly recycled contributes organic bulk and leads to soil improvement.
Most of the nutrients contained in a fertiliser if not used by the plants are retained in the soil. This is not true of nitrogen that is very readily washed away in Winter. Potassium and nutrients such as magnesium also leach if the soil is very sandy. Clay soils and soils high in organic matter retain such positively charged nutrients very well. Furthermore nutrients including nitrogen become part of the organic fabric of the soil. Phosphate scarcely washes in, never mind leaching out. Fertilisers lead to a build up in soil nutrient fertility.

We frequently read of gardeners trying to reduce rich soil fertility to grow wild flowers! It seems to be  very difficult especially regarding phosphate.

Perhaps phosphate is the achilles heal in my argument. It is recognised that many gardeners and farmers have over the years over-fertilised with phosphate which in consequence builds up in the soil. I can’t resist suggesting that in gardens it is that wretched bonemeal again! In truth most general fertilisers have too much phosphate in their ‘analysis’. The US state of Minnesota prescribes a legal maximum of phosphate in any fertiliser sold! 
If you have a thing about fertilisers I hasten to point out that high soil phosphate can arise  from manure too. As some reassurance I have never come across excess phosphate as a problem when advising gardeners.

A little story
I have always been somewhat eccentric and as one of my lecture subjects used to be soil management, I have done unconventional things to my soil to see what might happen. For much more than a decade after I got the no dig bug I refused to import any external organic matter to my vegetable allotment. All offers of manure from horsey neighbours were declined!
All the organic matter my plot generated was recycled (other than the tasty vegetables we ate!). Most of such fresh organic matter was merely left on the soil. I did frugally apply inorganic general fertiliser ‘top dressed’ on the surface around my plants.
Every year I would quote in my lectures how my soil had developed magnificent structure and had become ‘black with organic matter’. One day I had to give an important lecture and thought I ought to have the soil’s organic matter properly analysed. The level was off the top of any normal scale!

No dig gardening is now starting to be accepted. Most such gardeners still ‘don’t get it’ that you don’t actually need to import organic matter from external sources for the system to work! 
This is me being puritanical. Importing bulky organic matter is a speedy way of developing an organic rich soil structure and for most gardeners is the route to converting to no dig.
The point of my story is that my annual use of inorganic fertiliser did not prevent my soil developing a wonderful structure and in my opinion contributed to its beneficial transformation.

FYM is bulky and organic and is a manure and not a fertiliser. Its nutrient analysis is low but VERY SIGNIFICANT. Because of its bulk it adds substantial nutrients. A vegetable grower who applies it generously every year need never use fertiliser!

Some specific effects of fertilisers for better or worse
I will include lime in my comments. Although the main use of lime is to raise pH and make a soil less acid or even alkaline, it is a fertiliser too.
Indeed lime is widely held to improve soil structure. This might be disputed. The schoolboy lesson is to add limewater to a suspension of clay in a test tube. It immediately ‘flocculates out’ as the floating particles stick together. Some of us argue this gives a false impression as virtually the only time a soil is deflocculated is when it is flooded with seawater - as large tracts of south east England were in 1953. 
Some also suggest that lime improves soil structure because calcium is said to encourage worms.

My general fertiliser has been applied to correct the lawn fungus called red thread - a disease of infertility

Iron sulphate fertiliser’ applied to the lawn is a moss killer too
Salty tales
When the South coast was flooded massive amounts of sodium chloride were absorbed by the soil and its structure became a ruined sticky mess. The clay was deflocculated.
Destroyed by a chemical it was restored with another. Very large amounts of calcium sulphate were applied to the soil. Calcium sulphate is a lime that does not raise pH and its calcium ions displaced sodium ions on the clay. The clay became flocculated again, the sodium was leached away by subsequent rainfall and the rest is history!
This case illustrates that chemicals can destroy soil structure albeit in very exceptional circumstances.

Asparagus is a maritime plant and some gardeners apply small amounts of common salt to it as a fertiliser. This may or may not be a good thing but for asparagus, sodium and chloride are regarded as ‘trace elements’. Many other plants can also utilise sodium and/or chloride as trace elements. For some it is an obligate need, for others it is optional.
The thing about trace elements (in common with almost all chemicals we use in our life) is that small amounts are beneficial and even essential, larger quantities might be of no further consequence but very large doses are toxic. This applies to fertilisers too.

Fertilisers can be used to correct plant nutrient deficiency. This chlorosis has now been corrected by applying Yaramila (It might be the nitrogen, magnesium or trace element content that 'did it')

‘Salt’ can mean other things than sodium chloride. It is a term that includes chemicals that settle out of solution and some soils are saline which is not a good thing. Such soil salts may or may not be plant nutrients and may or may not have been supplied as fertilisers!
Saline soils occur worldwide. In the UK problems are restricted to greenhouse soils where insufficient irrigation allows salts to accumulate. Old time growers - I mean those in my youth - would copiously water in Winter to flush excess salts out. Very few horticulturists including amateurs grow direct in a greenhouse soil now although I myself do. Greenhouse growers are sometimes caught out when salt sensitive plants such as lettuce cease growing and die.
High levels of soluble materials in the soil restrict osmosis and plants ability to take up water.

The most frequent occurrences of salt concentration problems occur when gardeners place highly soluble fertilisers close to delicate roots or apply too strong liquid fertiliser feeding.

I have not exhausted all the examples of how soils, plants and fertilisers interact. Nor have I covered all the good and bad things about fertiliser use but have said enough for today.

  • My comment that phosphate - causing water pollution - does not leach from a soil does not apply to leachate from a compost heap standing on a hard surface that might wash direct into a drain. Nor to decaying leaf litter lying on a road. Nor to soil physically eroded into water.
  • I think it is about time I wrote about the considerable advantages of fertilisers when properly used
  • My previous fertiliser posts can be clicked in the theme column. Because google only usually brings up the last four posts there are two clickable titles.

Sunday 17 January 2016

Why is hybridisation still not generally considered to be a force in evolution?

For many hybridity is peripheral and others fervently reject it.

As a lifelong horticulturist I have always been intensely interested in evolution. To me it is a fact that that life as we know it has evolved from primitive beginnings.

I know as a gardener that many of our garden plants are hybrids. I read that most farm animals are too. Whenever I search the net for a story about the origins of any plant or animal I want to write about I invariably find hybridity is involved. Why don’t we learn more about it in our school evolutionary text books? Today I want to explore why.

Other than my biological background and intense interest I have no special knowledge of genetics. I struggle to understand much of what I read. When I discovered Gene McCarthy’s writings it was revealing that someone with his authority, intellect and lifetime dedication to genetics should believe hybridisation was a prime driver of evolution. Such notions had been knocked out of me at school. I shamelessly return to his writings whenever I have doubts. Reading McCarthy has brought home to me not only that hybridity is equally relevant to both plants and animals but that there is a mountain of evidence that hybridisation has always been common in nature and that known and frequently recorded genetic mechanisms exist that enable the results of hybridisation to join the evolutionary line. Or should I say lines?

Many geneticists take it as a given that hybridisation is significant in evolution. Perhaps it is so obvious it is not even worthy of their attention and spending time in foolish argument? 
In contrast, within narrow genetic specialisations others might not bother to address the big picture? Perhaps they don’t want to bang their heads against a brick wall? Perhaps backwoodsman cannot accept new thinking and change their mind.
Despite all the evidence the standard story of evolution is that hybridity somehow has very little or zero significance. They even use statistical techniques to remove genetic evidence to construct their pure family trees!

Most evolutionary texts emphasise that evolution has been in a completely straight line. No hesitation, no deviation just like an arrow. This implicitly rejects the notion of hybridisation.
On the other hand the concept of hybridisation does not  deny that all life has evolved from that first single spark. (Nor does it confirm it as a single event).
Hybridity does suggest that the path of evolution is somewhat striated, that new mutations can be shared, that chromosomes can be restructured and new genomes created.

The belief that the arrow of evolution is precisely a straight line denies that an evolutionary line can share with others exciting new options. An organism passes new configurations on to its own progeny but not others. Sexual sharing is limited within its own species.
One might reasonably argue that normal sexual exchange is a form of hybridity. Why is such sharing acceptable but is taboo when breeding occurs across so called ‘species barriers’?

Cathi’s soay sheep remain true to type as they interbreed freely. If they got together with a different breed of sheep they would  readily create a hybrid, albeit a genetically close one

Although evolution has no preordained direction, nature has proved endlessly innovative in its procession. Evolutionary mechanisms unimaginable to Darwin are now understood in everyday currency. Genes are now known to have undreamed of mobility from species to species. I cannot believe that hybridity across so called species ‘barriers’ has not been a powerful force in evolution’s speed and direction.
My subject today is to wonder why many people disagree.

Why is hybridisation swept under the carpet?
I attended a lecture recently where mention was made of a project on the distribution of trees and the success of significant varieties in a dissimilar range of European climates - thought to be of interest in terms of conservation. The speaker showed us a picture of the magnificently handsome best performing tree and in a lowered voice stated that it was an interspecific hybrid. There was a perceivable frisson.

Listening to Jim jal-khalili’s excellent programme where he interviews great scientists, his guest for the day was a man whose knowledge of the botany of cereals had transformed whisky production. He recalled his first job interview as a young man armed with his botanical degree(s). He was asked what he knew about wheat! His answer was “nothing” , his course did not include hybrids, they were not considered real plants!

Our language is pervaded with words that suggest ‘pure breeding’ is a good thing. Mongrels are regarded as inferior. In truth everyone knows that many mongrel dogs outperform expensive pure breds most of the time.

The popular perception of a mongrel

Rocking the boat
Half the world does not accept the fact of evolution. It’s deniers know no limits in their propaganda that demeans the concept. Not only have many such people never tried really to understand evolution, much of the believing public only sketchily comprehend it.
Since Darwin’s time much of the detail of his so called ‘theory’ has been expanded and generally confirm his brilliant deductions. He would have been delighted to know about mechanisms that have now been discovered that he could never have dreamed of. 
Charles Darwin himself was a great hybridist and wrote extensively about hybrids. He did not permit himself to speculate about them in ‘The Origin of Species’

New discoveries can be wrongly portrayed as original error. Proponents of evolution are hoist on their own petard in being dogmatic about certain aspects of the process and over simplifying explanations. To admit that hybrids are a fundamental part of the process gives deniers ammunition.

Fear of public ridicule
Darwin withheld from the public his insights most of his life. As a devout man he worried how it would impact on public belief. Perhaps he also feared ridicule. The suggestion that man was descended from the ancestor of a monkey was a startling revelation. (Scientists these days are a little more specific when they name our ancestor as a chimpanzee).

The huge range of modern pigs bare little resemblance to their wild ancestors

My inspiration, Eugene McCarthy has postulated that in addition to chimps that the pig  family also features in our early human ancestry. Only a hypothesis, not  a statement of fact. His website includes a very long list of human characteristics that we share with pigs and no other primate. I am inclined to believe McCarthy’s suggestion.

It is not my purpose today to persuade you of the right or wrongs of this hypothesis. My point is that takes a lot of courage for an eminent geneticist to share his ideas when they might destroy his reputation.
I was recently distressed to read a virulent and ignorant attack on Eugene McCarthy. Written on a blog that google statistics show to have thousands of followers, it demeans itself by suggesting that only an idiot would perpetrate such nonsense. It scornfully distorts McCarthy’s  achievements and creates a caricature of of his theories. It displays total ignorance of science when it distorts his opinions before it triumphantly knocks them down. Such a level of argument would disgrace kids in a schoolyard. When I showed it to Cathi she observed that those who shout loudest have usually lost the argument.
One of this man’s scathing ‘put downs’ revolved around the fact that pigs and monkeys are distant on the mammalian family tree. I was delighted to recently read that new genetic studies have placed the two lines very much closer together.
A female academic was more subtle in her insults. She writes that McCarthy was somehow given his PhD and that ‘he writes about birds’. Some understatement about  a world authority on bird hybridisation.

Diverse animals can be friends 

Public distaste

Sex rears its ugly head

Paleaolithic cave art. This picture has an enormous similarity to a roman depiction I have seen from Pompeii 

It’s easy to accept hybridity in plants where innocent albeit potentially promiscuous pollen is carried to the stigma by wind or animal transfer. Not so animals that indulge in copulation. Sex across species lines and animal behaviour that might involve incest for many is repugnant.

Bisquit’s father is his grandfather! 

Worse when one wishes to study reported cases of historic hybridisation there is a long history of records that include both the genuine and the manipulations of charlatans. We have a history of Victorian circus and a morbid interest in monsters.

Belief that hybridity is an evolutionary dead end and that hybrids are sterile

Hybrid crosses like the 'cockapoo' might become popular. I presume they are repeatedly created each time by the breeder producing a litter by hybridising a spaniel with a poodle. 
If cockapoos were to self fertilise over several generations and a breeder were to select in each new generation, they would eventually give a fertile pure breeding line.

When a horse and a donkey breed together a mule is created. It is a frequent occurrence. Much is made of the ‘fact’  that all mules are sterile and this is often quoted as evidence of the sterility of all hybrids. 
What might be true with mules is patently untrue as any gardener will testify in the cases of tens of thousands of hybrid plants. The same with animals, especially where crosses are not genetically very distant and in particular where different species and genera share the same chromosome number. 
More distant crosses are much less fertile and sometimes are not fertile at all. I have written in my previous posts about plant hybrids such as Primula kewensis originally sexually infertile which after many generations of vegetative propagation produced fertile seed. Many ‘more primitive’ animals also reproduce vegetatively and share this opportunity. (En passant I mention that this morning’s New Scientist carries an article on so called ‘virgin birth’ over multiple generations in sharks).

Some successful crosses might be extraordinarily rare. In terms of evolutionary time  ‘rare’ might be reinterpreted as ‘certain’.

If this palaeolithic cave art is thirty thousand years old and if we take a billion years of evolutionary time and scale it down to a 24 hour clock, then this painting was done at about three seconds to midnight. 

Take mules as an example of a rare case of an infertile hybrid producing offspring.  A geneticist estimated the chances of a mule procreating as one in five million. A dubious figure up or down! The figure of five million mules born must in earth’s history have been exceeded several times over and indeed as the mathematics would suggest there are reported examples of a very small number successfully breeding.

Mules are very fine animals and display hybrid vigour

Another objection often quoted in the case of hybrid plants is that although they may be produced by a successful cross and also be fertile, further seed production gives highly variable offspring. This is absolutely true! 
Such variation provides new opportunities for nature. And the plant breeder too. This is the stuff of evolution where selection from new innovations wends life on its way.
I suppose all those posh pure breeding dogs started as mongrels.

Teaching evolution
When the scientific community does not agree whether hybridity is a small blip in evolution's alleged beautiful straight line or is a prime driver by the process of sharing and the fabrication of new genomes it is not surprising that the public presentation of evolution is shallow.
Pity the poor teacher. For most subjects these days syllabuses are restrictive. How much more in a world where many do not accept evolution. Worse where their is ignorant resistance to teaching evolution at all.
It must be a delight to teach evolution to a group of eager young scientists. It must be hell on earth in a school where pupils have come to the class armed with preconceived  propaganda.
There is little scope for the teacher to speculate that the story of the descent of the horse although correct in outline is in detail seriously flawed. Nor to discuss the notion that many species appear in the fossil record with a relative suddenness and remain very little changed over millions of years.
It will be years before hybridity receives the attention it deserves.

Bisquit’s mother was unable to suckle and rejected him and he was raised by Cathi. Brenda was stepmother to feed him in the daytime. Now returned to his flock, whenever Cathi approaches he is first to come running

It’s amazing how variable a lamb’s diet can be when not in a field

This is the first of a new series about hybridisation. Below is a resumé of my previous posts

Hybridity 5. Traces the discovery of the Wollemi pine and relates the genetic mystery of why all wollemis whether raised from seed or vegetatively propagated are genetically identical. Also references to horizontal gene transfer and stabilization of new genomes

Hybridity 4. Metasequoia is not only a fossil tree that has maintained its genetic integrity over millions of years it is also thought to be the hybrid parent of the giant Sequoia sempervirens. Growing taxodium and metasequoia. Russian genetics and hybridisation, the evil Lysenko and the sad story of Vavilov. Taxodium fossils. References to ancient plants that hybridise freely

Hybridity 3.  Gene transfer across hybrid zones. The apparent ‘saltation’ of new organisms in the fossil record. The amazing ginkgo. Speculation that cycads might be an ancestor of Ginkgo. Tentative talk of hybridity in human ancestry

Hybridity 2. Numerous cases of garden hybrids including Leyland Cypress (hybrid vigour anyone?) The question is asked why with so many known and verified hybrids is it always assumed that any new species has developed by Darwinian ‘straight line’ selective mechanisms. The curious duck billed platypus that has bird and mammal characteristics, both in its physical structure and its genetic mechanisms. Similarity of a chicken to a dinosaur. Sarcastic comment about statistical binning

 Today’s New Scientist reports that the domestic chicken has been known to give parthenogenic birth

Hybridity 1. Numerous cases of garden hybrids. My own enlightenment to hybridity Examples of rapid ‘natural selection’ over very few generations. Gene transfer between microbes. Dogs, coyotes and wolves. Deficiencies of plant classification.

addendum January 2016
More negative publicity for the idea of hybridisation
Today’s morning newspapers, in their latter page headlines, splatter the notion that we inherited our ‘bad genes’ from the neanderthals. My paper states from ‘limited liaisons’ (we must not scare the children) that nicotine addiction and depression come from Neanderthal genes. Such information comes from research in Nashville, Tennessee where I understand they talk about nothing else other than evolution.

My hackles rose at the suggestions of human superiority and the implication that other neanderthal genes will not have made positive contributions in our genesis. The way that the press report the research we are left with the notion that hybridisation although generally insignificant is also a bad thing.

Sunday 10 January 2016

Slug control. More about molluscs

Are gastropods really so ghastly?
I will frequently state ‘slugs’ when I mean slugs and snails

My first opus on slugs and snails was posted two years ago and very few read it. In contrast every time I talk to gardening groups everyone asks about them. I wonder where I go wrong. Perhaps there is so much rubbish out there that my own slippery contribution is google linked on an exceedingly high page. 

Slugs and snails are the only molluscs that have emerged from the water to live on land. Slugs and snails love wet conditions! If drainage is poor and it is a wet season they will give gardeners a problem.
Not only do slugs thrive when it is wet, control measures that use metaldehyde based slug pellets often fail at that time. Not only is the dose of poison less likely to kill them but pellets when wet are much less attractive.

Slugs love organic matter but that is no reason to remove it
There has been an awful lot of organic matter on the surface of my vegetable garden this Winter with debris from cleaning my ponds (It will be redistributed in Spring)
How ever often gardeners read about the horticultural benefits of organic matter they still remove it in the misplaced interest of hygiene and tidiness. The latter I can understand although I don’t share this quality. Compost and manure are deemed desirable but not dead weeds, leaves and other debris. 
I always complain that when nature offers to add organic matter to the garden that tidy fusspots spurn it. Some gardeners even feel guilty if they hide a dead hand-pulled weed behind a tall plant. I do not bother to disguise mine expecting them to quickly shrivel and benefit the soil. 

Quelle horreur, organic debris might even attract slugs. This might be so, but what could be better than them acting as nature intended. Let them rasp away any dead vegetation and start the first stage of natural organic decay. Better eat this than your plants. And they prefer it.

Look at slugs differently 
You will always have slugs and snails. Their rate of procreation is little effected by lots of debris. There are other significant influences on their rate of breeding including  a gardener’s diligent destruction. The quicker you kill those species whose fecundity is effected by the number of slime trails they crawl over the more they will breed. 
Slugs can travel considerable distances to come to your garden. If they find it surgically clean of plant debris they are so much more likely to eat the leaves of your plants. 

Big black one

Do minimum cultivation methods minimise slug and snail damage?
I personally think so and the more I read I find others agree. The closer a soil is to nature the greater the likelihood of natural control. For example there will be more hungry black shiny highly mobile ground  beetles to devour slugs and snails. It is ironic that so many gardeners inadvertently drown ground beetles in childish slug pubs!
There is more slug damage to seedlings in loose fluffy seed beds. Farmers are advised to make firm seedbeds and avoid lumpy clods. Deep sowing apparently helps minimise slug damage to seedlings and agricultural advisors  frequently recommend deep firm sowing to growers of grain.
I will explore the theme that there will be less slugs with minimum cultivation in a future post.
They come in all colours

Use of slug pellets
This is the normal control used by farmers and growers whose produce would never sell if there was even a hint of slug damage. Slugs in a lettuce might ruin a reputation. In the middle of a cabbage slugs don’t endear you to your culinary cutie.

Gardener’s worry pellets are a problem to wild life. If used sparingly and responsibly and in limited circumstances I don’t really think so. The real danger of their poison is that domestic animals might ingest a quantity from an unprotected packet. There have been several tragedies. I personally remember with sadness a doctor whose dog died after devouring a pot full left in her greenhouse.

Slug pellets are a bran bait charged with poisonous metaldehyde. They also contain a chemical that makes them highly unpalatable to animals and birds. The bait attracts slugs and it acts over several centimetres. In my opinion no more than half a dozen pellets per square meter are needed. I deplore gardeners who apply pellets enough to create a blue mulch. That is how real harm is done. Rates of application of pellets on a farm will be no more than about four kilograms of pellets, (not raw metaldehyde) per hectare. That’s far sparser than the quantity applied by the ignorant and ecologically uncaring.
Four kilogram per hectare per hectare is four gram per ten square metres.
Why that means with my gardener’s arithmetic that an ounce of pellets would cover eighty square yards!
I have six acres of garden and one small pot of slug pellets last me over two years. Most of my gardens receive no slug control whatsoever!

My own Yaramila fertiliser is a blue prill and I sometimes imagine visitors think I have been scattering slug pellets! Even my fertiliser is spread much more thinly than some idiots slather on pellets.
I secretly suspect that the irritant action of my highly soluble fertiliser in the vicinity of a newly planted cabbage might be a slight slug deterrent but unfortunately not after it has rained.

Gardeners forget that pellets are a bait and sometimes apply them close to their plants. The incoming slugs or snails are very likely to prefer lettuce to the bran. Spread pellets widely over the whole patch of any new planting in your vegetable garden and then go a little wider. Best to attract the slugs away. If I suspect my newly planted sweet corn might be vulnerable, I spread a few pellets the day before planting. (On the rare occasions I remember to spread any at all!)
It is sometimes possible to cover your slug pellets. Not only does it keep them dry it might hide them from birds. Unfortunately dead poisoned slugs are toxic too. 

A couple of grey ones
I sometimes get slugs in my greenhouse and occasionally use slug pellets. Only on the bench if as usual there is a frog on the ground! Frogs from my ponds love the plant nursery outside my greenhouse and often migrate inside through its crumbling wall.

Remember too that slug pellets under a plant canopy such as ground covering hostas will be hid from the birds.

Snails have made a real mess of Steven’s yucca. If the odd slug pellet lodged in the leaves it might help
I once visited a famous garden in Seattle. Our guide casually stated that they did their annual slug kill in March. Whatever did he mean?  No gardener challenged him. I imagine they thinly spread slug pellets all over the garden. Just like a farmer covering the whole of his field. I imagine such a cover is quite effective as slugs and snails travel more than you  imagine.
In my opinion the ornamental perennial garden needs no treatment at all -  except for the hostas.... and perhaps the delphiniums not to mention the….

I read that the organic establishment in ‘force majeur’ situations sometimes gives a special licence to their members to use slug pellets based on iron phosphate. Having read this article I think they might be misguided. As the author states ‘alternative medicines’ often escape proper safety controls.

How damaging can slugs be in the garden?
There are two types of gardener. Those who take slugs in their stride and marginally adjust their methods to accommodate them. Others become neurotic and despair when they are insulted by even the slightest scar. They go out at night with torches and salt and buy geeky products.They spend a small fortune on biological control. Just for a few carrots!

When cutting back my hellebore in December I found these snails. I did not have the heart to kill them and they remained there a couple of days before they slithered away.

Most plants are hardly effected by slugs at all. There are however some circumstances where plants are very susceptible and damage may be severe.
Often the problems are associated with the production of vegetables and plants such as strawberries. Damage might be severe where soft plants are raised inside and planted outside. Damage might be  be particularly nasty if the weather is wet and cold and plant establishment is slow. Plants that are in any way stressed and wilted, often newly planted, attract slugs. Perhaps the nearer to death the more slug friendly your plants are.

Dare I call this a slug club? The snails take a break in Summer, especially when it is dry and hibernate in Winter. My pile of bricks (used to anchor and build up walls for my fleece) is always fully booked.

What else can I do?
Many species of slugs and snails do not feed on garden plants at all. They browse on algae and fungal green slime and eat decaying vegetation.  Don’t waste your time killing these kinds. Heed the old country saying
If it is black put it back
If it is grey, keep it at bay
Unfortunately that does not apply to those black slugs eating your potatoes!

So here are a few tips...
Encourage birds
Encourage frogs, have a garden pond 
Traditional East Yorkshire gardeners kept a toad in their greenhouse
Hedgehogs can eat 500 slugs in a night
Sometimes susceptible crops such as potatoes have more resistant varieties.
Use avoidance strategies such as early lifting of root crops
Plant sacrifice plants as a decoy for slugs
Listen to Mr Foolhilly….

I believe that slug 'problems' are of our own making and stem from a seriously distorted perspective of 'what a garden should look like'. Orderly rows, clean soil and immaculately manicured lawns and hedgerows are so alien to nature that we create terrible distortions of balance - that all too critical component of nature’s stability. This is often compounded by our overpopulation with the consequence that a 'garden' can often be as tiny as a container or two. In such tiny portions, nature finds it near impossible to establish any sense of balance.

When I took over my field, it had been used extensively as agricultural smallholding for many decades. I planted a third of it with wheat (for the chickens). It was a wet year and every ear was smothered with small grey keel slugs. My first stab at re-establishing a sense of balance came with the release of half a dozen Khaki Campbells. For weeks, their crops were gorged with a rich diet of slug protein. For the ducks to harvest the slugs, they had to be able to be active by first light, so they were left un-cooped - the local foxes soon dined well on recycled slug…

Read the rest of Fool’s comment in my previous post about slugs and snails

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