Wednesday 28 February 2018

Garden myth or truth?

Healthy Yorkshire food
In writing about gardening myths I sometimes find a grain of truth within them. So too today.

Canadian sleuth Robert Pavlis hunts down gardening myths with great zeal. His blog is solely about gardening myths and his mind is endlessly fertile in seeking and finding fantasy in most unlikely places. His research is precise and he freely provides his own evidence base. 
He does home based experiments that expose silly notions. His particular targets are snake oil salesman who brazenly repeat the most outrageous product claims which he fearlessly exposes. I do get the impression that over the pond the public are more gullible than here.

Robert’s discoveries frequently surprise me.
A few weeks ago he published his personal top ten myths of the year. I have picked out two to which I have in the past been an unthinking believer and shamelessly admit that my post today plunders his thunder.

Myth *1. Eating rhubarb leaves will kill you …. and it’s the oxalic acid ‘what did it’ 

Not very appetising
Actually two myths in one. You would have to eat oodles of rhubarb leaves to come to harm… and if you do die  it isn’t the oxalic acid!

Most vegetables contain natural plant toxins. They are their natural defences to pest and disease. Indeed many scientists wonder if the toxins are the reason why vegetables are good for us! The scientific principle is known as hormesis and in a nutshell this hypothesis states ‘a little of what is bad for you does you good’.

It would take 25 grams of oxalic acid to kill us. That is a massive amount. Robert calculates you would need to eat a serving of 5kg of rhubarb leaves. I think he might be wrong in as much as most laboratory measures are ‘dry weight’ in which cases it would take very much more.

I believe Robert about the oxalic acid but am not minded to try the leaves
Where it gets interesting is that the oxalic acid in rhubarb leaves is  .5 gram/100gm whereas the ‘leaf stalks’ you eat contain  .45 gram/100gm. Almost identical - no real difference at all!

Weight for weight same oxalic acid content
Even more revealing is that oxalic acid is very common in many other vegetables. Carrots and radish, weight for weight, contain exactly the same oxalic acid as rhubarb leaves. Spinach contains twice as much, chives three times so and parsley a whopping great four.

Three times the oxalic acid
There is no way I will forgo my healthy parsley and egg sandwiches or parsley sauce with my fish pie.

Robert suggests that if small quantities of rhubarb leaves really do harm you the culprit might be anthraquinone glycosides. Even so there are today almost no (or even any) reported deaths of anyone eating rhubarb leaves. With their known laxative properties and no doubt horrible taste there are better ways to go.

Guess what I am thinking?
A medical drug extracted from crushed rhubarb roots was once highly prized and very expensive a little more than a century ago and has been fought over from ancient times. In the seventeenth century so called rhacoma root was three times the price of opium.

Myth *2  Adding peat acidifies your soil

Well of course it does but is the fall in pH significant or long lasting? The answer is a qualified no. 

Granulated sphagnum peat
Although I have long considered adding peat to improve a soil as extravagant and arguably environmentally irresponsible I do fear that on public platforms I might have recommended peat to acidify soil. It’s amazing what rubbish gardening experts utter when the listening public expects you to know.
( I do not regard it environmentally irresponsible to use peat as a compost ingredient although regular readers will know I do not use peat in compost myself)

The thrust of Robert’s argument Is that if your soil contains calcareous matter as alkaline soils invariably do then the capacity of the soil minerals to raise pH change is huge compared to peat’s puny capacity to lower it.  Scientists call this resistance ‘buffering capacity’.

Put the argument another way. If you are using a completely peat compost you need very little lime to make your compost as alkaline as pH 8. and to maintain it as such for a fairly long time. 
Recall that the mineral content of calcareous soil is lime. Recall too that some peats such as ‘Somerset peat’ form in alkaline conditions and are naturally alkaline.

Soils whose mineral content is mainly silt and/or sand will have less of a buffering capacity that resists soil acidification by adding peat - but often such soils will already be acid

The above argument overlooks that the fact that adding peat might improve the physical nature of your soil and that incorporating peat might improve the growth of acid lovers such as rhododendrons. But please don’t expect miracles on chalk or limestone soils.

These peat blocks were once very popular for making peat beds
Where peat excels is to grow acid loving plants in raised beds of pure peat and other acid ingredients or better, use it in tubs. It needs to be raised otherwise the alkaline water leaching from soil will soon make it alkaline.
(One of Robert Pavlis’s correspondents wrote that in the USA  they grow their precious blueberries on a buried peat bale and that works very well for several years}.


I wrote about how to grow rhubarb and lapsed into Yorkshire dialect

We visited a rhubarb farm

I spoke up for peat compost

I could not resist using this picture on this particular snowy morning

Monday 19 February 2018

Follow my narcissus and daffodils through a season.

Two (and a bit) edited posts republished from 2013

In 2015 I published this picture and invited a name - but had no takers. That year it flowered the third week in January

This year, 2018, my daffodil has been continuously standing in water for eight weeks since it emerged. Now in mid February it is still healthy and about to flower
This late season in 2018, February Gold is only just emerging
1. First half of the season 
I am lumping them together, they are all narcissus. Daffodils are the ones with the large trumpets. I love them all, but perhaps daffodils most. They are so popular, that some complain they are over-planted. 
I once read that a particular variety, I forget which one, made up the greatest total mass of vegetatively propagated identical genetic material in the world! This might be wrong but there are tons and tons of it around.

Apart from their bold beauty, I adore narcissus because they hold their flowers a long time, there is a huge range of varieties and species, and by planting a sequence of early, intermediate and late varieties you can enjoy flowers for up to five months.

Narcissus are  wonderful for naturalising. Planted in the ground they become stronger each passing year and thrive in a huge range of soils. A man on the television recently said they are intolerant of poor drainage. How wrong can you be. Had he never seen the beautiful drifts of daffodils in Farndale, North Yorkshire.There, they are frequently flooded, and grow right to the water’s edge. I see snowdrops in wet conditions too but never hyacinths and tulips.

A little worse for wear these daffodils have been under water for a month.
Follow my narcissus this year
I am intending, in this blog, to follow my own daffodils as they progress throughout this coming year. Other than those in tubs they are all permanently planted. 

In beds and borders
The snowdrops were there first!
Provided you don’t dig, narcissus can stay in place for years. It is best to plant new bulbs before the end of September - unlike tulips where if necessary, you can wait until Christmas! I try a few new varieties each year.There is an enticing range and they are not all yellow! I plant mine in discrete clumps where they have room to die down in sunshine before being overgrown by summer vegetation. 
Be aware that the changing landscape of a garden such as the growth of shrubs and trees may eventually heavily shade bulbs. When this happens either prune the bushes or transplant the bulbs. Do not be afraid to move them ‘in the green’, otherwise you might forget their location! Shaded bulbs ‘go to grass’ and will not flower. But read on, do not throw them away! 

In tubs and planters outside.
I make up a few new tubs each year, others I refurbish and some I do not disturb at all. Eventually with the ravages of time, animals and neglect, they subside and any surviving bulbs can be convalesced to permanent planting in the ground.
Because it is sandy, I can use my soil instead of compost in tubs. I prepare soil with slow-release fertilizer, dolomitic limestone (it’s my choice of lime) and very judicious use of NPK compound fertilizer. More cautious gardeners might use John Innes No.2 compost instead. My new bulbs come from Parkers Wholesale and all my Spring bulbs are planted well before the end of September. They remain in my ‘nursery’ alongside my greenhouse, until they burst into growth and are ready to display. 
Established tubs are given a top dressing of my Yara Mila compound fertilizer in August and January. Growmore is a suitable but inferior alternative. (I do not use any fertilizers on my bulbs in the ground).
An important cultural note. In tubs in winter it is easy to become complacent with watering. As bulbs become leafy, in dry windy weather, the soil is quickly dehydrated and they then need plenty of water. I have frequently seen bulbs in containers damaged by severe water loss in drying conditions.

In grass

Narcissus (together with crocus and snowdrops) are one of the few bulbs with the constitution to naturalise in grass. It is traditional practice to fling bulbs over the ground to mark a random pattern for planting. I only recommend this if there are swathes of grass you do not intend to mow until the bulbs have died down. In my own case I want to regularly mow between them and just as I do in my borders  plant  my bulbs in random clumps. As to actual planting I use my border spade to lever-up the grass, shove in a handful of bulbs and tread down. Fancy bulb planters are of no use to me.

In the wild
My house was originally two farm cottages and is more than two hundred years old. I imagine a householder collected native lenten lilies ‘in the wild’ and planting them in the hedgerow across the farm track, now a busy road! They are still there and set seed. With a little encouragement from me they have made very strong clumps and some (with my help) have migrated across the road to my own grass verge.

In my two cemetery gardens there are many thousands of daffodils, snowdrops and bluebells. Planted on graves going back a hundred and fifty years, the narcissus had all ‘gone to grass’ and did not flower. This was a result of the heavy cover of weed. Nettles, brambles, ground elder, couch, horse radish with roots thicker than you arm, you name a weed, it was there. It took a couple of years of my Roundup sprays to eliminate the weed. It took two to three years of sunshine for the bulbs to return to flower but they all did. With no further attention other than keeping them weed free, they continue to flourish at Bolton Percy after nearly 40 years. What happened at Bolton Percy ‘by accident‘ was repeated at  Worsbrough fifteen years ago, this time with intent. It was a delight to watch the same succession back to flower. 

Anticipated pleasures later this season

You will recognize a superior camera skill to my own. Harry had been  commissioned for a book about York.

2. Down daffy lily, the continuing daffodil season

It’s been a good year for daffodils. My earlier post examined the start of my own daffodil season. This post now examines how the season progressed. In particular I want describe how I try to ensure strong daffodil bulbs for next year. 

It’s ironic I posted a picture of an early narcissus in mid January when we had a warm spell. Two months of cold dehydrating biting winds that followed held later varieties back. Never have I known standard varieties to be so late but how magnificent when they eventually flowered. My advice to remember to water bulbs in outdoor containers and not let them dry out in dehydrating winds proved particularly sound. The reward for a gardener’s patience was that when flowers eventually appeared in the prevailing cool conditions they lasted a long time.

 Rip van Winkle
How to let daffodils die down
Don’t cut them back too soon. Preferably don’t cut them back at all and let them die down naturally. Thousands of daffodils in my cemetery gardens just fade away without any attention whatsoever.
Inexperienced gardeners sometimes do not realise that leaves need to photosynthesis and build up strong bulbs for the next year. After flowering the leaves need to remain green. For bulbs in containers, or those that have been lifted (not recommended) watering is still needed. Don’t let them dry out until they seriously yellow. Give them full natural light. Do not tidy them away behind an old shed! 
Some gardeners imagine the leaves just need to die down and translocate their stored reserves to the new bulb. Not true, the leaves need to continue working in the sunshine for as long as possible. It horrifies me how people who have had bulbs in the house (itself a great cruelty) just dump them outside in the cold in a shady corner and wonder why they do not flower again!

It's the middle of May. It will be many weeks before this late variety can be cut down

Do you know there are still some people around who after flowering tie the tops of their narcissus in knots? Yes really! How ugly, how decadent! Apart from being visually repulsive those poor leaves cannot do their essential work. I sometimes hear protestations to my ire, “but they still flower”. They might, but next year there will be less flowers, they will be weak and insipid and not last very long. Flowers should remain in their pomp for at least three weeks if the bulbs are strong (unless the weather happens to be very warm).
I once had a client, dear Mrs Blunt. Her daffodils really where too tall for her small spaces. Of course I refused to strangulate the green leaves. After my maintenance visit the arthritic the old lady would be down on her knees….
Another acquaintance said he thought tying in knots is what you had to do…..

Also relevant to building up a strong bulb is nutrition. When naturalised in the open ground daffodils normally need no fertilizer at all. In tubs and containers which are inevitably subject to leaching, although feeding will do little to improve flower quality in the current season, it is worthwhile if a sturdy bulb is to be achieved for the next year. I apply a top dressing of fertilizer to my tubs in September when my bulbs are building their root system and again in January when the foliage starts to grow.

Does dead heading help?
In another week these will be ready for dead heading

Ready to deadhead
Dead headed. I like spiky green leaves. Why on earth do some gardeners think these elegant leaves ugly?
None of the thousands of daffodils in my ‘natural gardens’ are dead headed but they still flower well in the next year. At home Brenda cuts off the dead flowers (but not the stalk). It probably helps that energy is not diverted into the seed head. The bulb production industry would seem to take this view with all those otherwise unwanted flowers, profusely displayed at spring bulb festivals. There are many bulbs such as my own native lenten lilies, dwarf tulips, scilla and chinodoxa that set viable seed. Do not dead head them!

I have never found Narcissus bulbocodium to naturalise from seed - but they bulk up vegetatively very well
Why bulbs ‘go to grass’ and fail to flower.

Apart from the obvious, when men on their ride-on-mower toys cut back too soon to achieve their wretched stripes, there are more subtle reasons why daffodils don’t flower. Usually the reasons involve excessive shade.
  • Planting under evergreen trees.
  • Diminishing light levels over the years as neighbouring plants in a developing garden grow tall.
  • Failing to properly manage bulbs in containers after they have flowered.
  • Being overgrown by tall weeds.
  • Following the calendar as to when to cut down. The leaves  should be distinctly brown and this will vary with the season and whether they are early or late flowering varieties. This year my lenten lilies were mown on the seventh of June. Now in early July several varieties remain uncut.
  • Sometimes when light levels are marginal and the spring weather is dull some bulbs might miss flowering the following year.
If your bulbs have ‘gone to grass’ providing they are healthy and are not infected by an endemic pest or disease, do not throw them away. It might take a year or two but they will  return to flower -  if you let them have the sunshine they crave!

Although this is planted in grass under my ceder it has plenty open sky to give enough light to flower well each succeeding year
Mowing strategy
As mentioned in my earlier post when I plant daffodils in grass I like to do so in clumps which  can easily be mown around. You will see in some of my pictures, that if you choose, you can mow very tight to the bulbs to allow very little long grass. In other places the tufts of longer grass look rather nice. As the leaves start to fade at the end of the season I tend to mow closer to the bulb. In some cases mowing a clump completely down is a gradual operation over three or four weekly mowings and I do not need to adjust the height of cut of my unboxed rotary mulch-mower. For larger grassy clumps when I make the decision to completely cut down I do raise the height of cut so the engine does not stall! Because I have a wide range of daffodils some early, some late, the whole process is gradual and is spread over several weeks. When long grass is suddenly cut short it will remain yellow for a while. By my open day in mid July in a normal year the last brown scar is just about gone! 

Little long grass where I mow close to the bulb
I will have to raise the height of cut when I soon mow this
On the the next cut these will be shredded and mulched to the ground. Not the one on the right, it's too soon
Another pet hate
Worse than tying in knots is cutting green leaves half way down. I go to the Worsbrough cemetery and on some graves I see it and despair.


It has just dawned me that David Willis will tell me its name
I wrote about David's daffodils here
wrote about snowdrops last year

Friday 16 February 2018

Evolution of new species through natural hybridisation

More evidence of hybridisation’s contribution to evolution

Hybridisation is starting to be accepted as a major contributor to evolution. 
The word ‘hybridisation’ is no longer a stigma and less often are hybrids  referred to in whispered euphemisms such as ‘mosaic’ or ‘mixture of modern and archaic features’ or merely ‘unusual event’. Unfortunately ‘rare’ seems to be mandatory in the report of any new finding.

The world's tallest tree Sequoia sempervirens is an ancient hybrid between the two species below

In point of fact it is virtually mainstream botany that half the world’s plants are hybrids.Yes, the world’s plants not just those in your garden. Considering that hybridisation has existed since sex was ‘invented’ I cannot believe that hybridisation  has not contributed to the evolution of all plants in their long history. And all animals too. It is now freely acknowledged that hybridity is significant in the evolution of fishes and birds but there is still a reluctance to agree that it makes much of a contribution in mammals. Despite emerging evidence of our own hybrid origins.

The idea that some scientists now challenge is that evolution of an individual organism is in a straight line from life’s very beginning; instead they consider life’s advance is an evolutionary line of genetic data since the very first ‘replicator’. The difference is that each small genetic move forward that has occurred over evolutionary time as a mutation in one of countless billions of organisms can be shared.

It has long been recognised that mutations within a species are shared by sexual reproduction. New human characteristics such as tolerance to alcohol might have occurred by mutation once or at the most a very few times. Billions of us now, thankfully, carry that ‘gene’.

There are often evolutionary barriers to breeding between species. Fortunately such barriers are often so weak as to be none existent or leak like a colander. Gene transfer between species is essentially the same as within a species.
It is claimed that hybridisation only occurs between very similar species. Ironically the meaning of ‘similar species’ can be defined as those known to breed together!

Hybridisation tends to take place between similar organisms whose natural distributions overlap. This occurs frequently as measured on an evolutionary scale. Even on an everyday basis where huge natural populations overlap fertile hybrids are routinely found. Normally they quickly disappear as they and their offspring are swamped by repeatedly back crossing with the most available parent species. Never-the-less genes have moved over and those that are advantageous will persist by natural selection in a new population.
Not only will genes cross over and multiply in mutually compatible species they can in turn be passed on in a multitude of new lines by further hybridisation ‘events’.

Intergeneric hybrids between muscovy ducks and mallards are relatively common but are sterile. This does not mean that mallards and muscovys do not share genes that have introgressed via past intermediate hybridisations
Such movement of genes across species barriers is a well recognised unchallenged phenomenon known as introgression. Really useful new mutations will be passed on in endlessly long chains.
Introgressed genes often go unrecognised and might mutate or take on new functions in emerging genomes; introgression makes no obvious challenge to the still standard dogma of new species developing in straight lines. Even now some evolutionists are blind to introgression’s contribution.

The imprint of hybridisation on life's evolutionary tree

How do you imagine life's tree?
Although hybridity fundamentally challenges the classical  tree-like representation of ‘the progression of evolution’ the broad direction of life’s arrow remains broadly as that usually portrayed.

Ever open to reinterpretation as new knowledge emerges it is now necessary to recognise that life’s tree is not a series of completely straight lines. 
The analogy might be better represented as a weaving of an almost infinite number of strands. The trunk and branches and twigs of the tree might remain but imagined filaments within have continually separated and merged. Such an analogy might be extended by showing some of the twigs grafting together.

It would seem that life’s evolutionary tree does not have much of a trunk. It would seem to be more a very straggly series of suckers. I wonder what appropriate plant analogy readers would choose.

Speciation as a result of hybridisation

Very common In plants, evolution of a new species as a result of hybridisation in animals is poorly documented. Indeed ancient hybridisations are overlooked and almost impossible to recognise. (Until recently no-one was looking
and as already explained introgressed genes offer no obvious challenge to standard theory). 

The thrust of today’s post is to report three very thoroughly researched new examples of hybrid species

1.The Galapagos finches

Said to be the inspiration to Darwin’s insights into natural selection in isolated communities it has long been suspected that the emergence of new species of finches involved some degree of hybridisation and examples have been found. Now an example of the process has been observed and closely recorded since 1981.

Flew 65 miles
Reported on the BBC website a resident team of researchers on the Galapagos island of Daphne Major observed a Large Cactus Finch male had arrived from its native island 65 miles away. It successfully mated with a local Ground Finch and and after only one back-cross the distinct and larger new form only mated within its own community. Apparently the local finches fail to recognise it's mating call. The new species has maintained its integrity and now numbers more than thirty. It exploits a new food source where it does not compete with the local population.

It is often a feature of a new hybrid that it lives or dies depending on whether it finds a niche. Unlike ‘regular’ natural selection where an organism by a series of small changes evolves to suit its habitat, a hybrid only survives if it finds a suitable niche. This explains why most recorded successfully stabilised hybridisations are where there has been dramatic rapid changes in habitats - by for example, climate change or human interference.

2. The Golden Crowned Manakin

The snow capped manakinJOHN JENNENS / PUBLIC DOMAIN
The golden crowned manakin  popped out of the Amazon jungle in 1957 and was only documented again in 2002. Populations have recently been studied and genetic analysis and comparative anatomy show it to be a hybrid species 180,000 years old. It had been previously thought to be a rare hybrid aberration destined to die or be subsumed by repeated backcrossing.

Researchers associated with Toronto Scarborough University have shown it to be a hybrid between the geographically overlapping Opal Crowned Manakin and the Snowcapped Manakin. The remarkable thing is that although capable of fertile mating with either of the parent species it has maintained its integrity for 180 000 years.

A rather nice outcome is that the researchers say  - and  hopefully not merely surmise, that the result of the original cross has been modified by natural selection over intervening time. If true it is a revealing amalgam of a distinct evolutionary hybrid ‘jump’ to a new genome and subsequent slow change.
The research scientists suggest that such hybridisation might be a more significant force in evolution than previously thought.
The light is slowly dawning

3. The Clymene dolphin

Its origin has long been somewhat of a puzzle, it was thought to be a subspecies of the spinner dolphin. It was recognised as a distinct species in 1981. Recent investigation using molecular analysis show it to be a hybrid between the spinner dolphin and the striped dolphin. 

To me the significance of this discovery is that it is reported on the Richard Dawkins Foundation website. My hero has long been at the forefront of genetic research and its promotion. What better evidence is there of an evolution in thinking?

Harry's pictures
Cathi has passed these over to illustrate this post. Too good to miss, all the birds are known to be capable of hybridisation.

                          Our own finches

Behave yourself
I am the only one here normal

The new finch
The golden manakin
The clymene dolphin
My earlier post about introgression

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