Monday 27 April 2015

Garden Open Day, Saturday 9th May 2015: zero inflation at Weathervane House

Come to Seaton Ross in Sunny East Yorkshire!

If any of my posts have any credibility they bear the hand of Peter Williams who lives down in the village. 
Peter and Julie Williams did not open their garden last year so now is your chance to see their garden again. If you have never been before you will be amazed and enchanted!

Peter tells me that the entrance ticket is £3 the same as his first opening five years ago. Please note his opening is on a SATURDAY - which is less usual for the Open Garden Scheme. The time is eleven until four.
Apart from  Weathervane House being one of the best gardens in Yorkshire, Julie is renowned for her wonderful cakes. 
I am used to extolling Brenda’s culinary virtues  when my own garden is open. Peter tells me that at one of his recent lectures he was told how fantastic Brenda’s teas were. They were very sorry but they had no memory whatsoever of my garden! Julie has more competition - their garden is unforgettable!

Seaton Ross is one of very few places in the York region to have acid soil. Peter grows  wonderful rhododendrons, azaleas and magnolias and very much more. Just come and look at and feel his wonderful soil. I have hitherto regarded the soil that we share as a very fine sand. Peter is a soil scientist and insists it’s a coarse silt! I have recently conceded to his superior knowledge.
In my defence he had published last week this fine article about rhododendrons in the journal of the Hardy Plant Society - which I recommend that you join. At the end of the article is a quote from the map of East Yorkshire. It characterises our local  soil as ‘very wet acid sand of low fertility’. His plants don’t agree

If you meet a talkative friendly diminutive Welshman as you walk round it will be Peter. Make yourself known. If anything pleases him more than talking about his garden it is explaining the science of how plants grow.

I am not sure how much of Peter’s five acres is open. Most of it will be and there is so much to see. Allow yourself plenty of time. Allow a little more time and walk round our lovely village. The village plot down the road will be blue with forget-me-nots!

2014 and 2015 pictures

Peter grafted most of his trees

Fingers crossed the rhododendrons will be looking like this  

Cornus florida is a beautiful shrub

Corylopsis sinensis will have gone over

Walk the grass paths and enjoy the ground cover that grows in the cool understory of fine shrubs

No doves in the dovecot.

Many bulbs are planted in drifts
Star wars will be over 

It’s always distressing to a garden owner that his best plants are finished by Open Day. But what joy when something overlooked makes a fantastic display!

There are sure to be plenty of cut leaf maples in the plant sale. They are one of the garden’s signatures

All the plants in the plant sale are grown to the best professional quality but are considerably cheaper. The large polythene tunnel is very useful if it rains

Whoops, I showed Julie’s cakes last year. They will be just as good this time! Indeed they are so famous the NGS link shows them too!

Advance information on another garden event

Seaton Ross gardens will be open on 7th of June. I will be giving it blatant publicity soon. 

Saturday 25 April 2015

How significant are soil bacteria to the gardener?

Just let them get on with their lives!

Relevance to manure and fertiliser
I had intended to put this post in my ‘myth’ series and wanted to decry the promotion of organic fertilisers as being beneficial because they encourage bacteria. I found myself in some difficulty!
How could I say that bacteria are hugely significant to the life of the soil and yet most things the gardener might consciously do to promote them be irrelevant? 
In the case of many fertilisers, they do have an effect on specific bacteria, it’s just that the overall benefit on the health of the soil is small and inconsequential. 

Any organic material added to the garden is food for bacteria. Nitrogenous organic fertiliser will stimulate those bacteria that degrade the fertiliser and beneficially make soluble its nutrient content. Although I do not generally recommend organic fertilisers, I admit they are of horticultural value in that they supply nutrients  - my issue is that the fact that bacteria are involved in nutrient release is quite incidental and not a reason to buy them.

Fertilisers versus manures

Farmyard manure is the very best bulky organic material to add to your soil. Because there is a lot of it, it will significantly increase soil bacterial action. 
Although its nutrients are NOT very concentrated because of the bulk the total nutrients added are significant too (provided they have not been leached out in a field!)

Fertiliser is quite different to bulky organic soil additives which are often described in the UK, not with strict accuracy, as ‘manures’. Unlike bulky organic additives, fertiliser is a concentrated source of nutrients and is applied to the soil in very small quantities. Dried blood, bonemeal, fishmeal and seaweed extracts are examples of organic fertilisers. 

Poultry droppings, although strictly a manure if you define ‘manure’ on the basis that it comes out of the back end of an animal, is best treated as a fertiliser because of its lack of bulk and exceedingly high nitrogen content.

Sulphate of ammonia, sulphate of potash and growmore are examples of inorganic fertilisers. They also effect soil bacteria when for example, ammonium fertilisers are converted by bacteria to nitrate.
When sulphate of ammonia is added to the soil, bacteria convert the ammonium to nitrate and and slightly acidify the soil in the process. In addition the sulphate content has an acidifying action. On my lawn I regard these effects as a very good thing!

Both organic and inorganic fertilisers do effect soil bacteria but in such a small way that such bacteria are unworthy of a gardener’s consideration

Bulky organics such as horse and cow manure, garden compost or ‘leaf mould’ are by definition both organic and bulky and do have substantial effects on soil bacteria. We add such ‘manures’ to the soil for many reasons including plant nutrition but perhaps most importantly for their physical effects on soil structure. It is a moot point whether their undoubted considerable effect on bacteria is a significant reason to chose them.

Bacterial myths the Canadian way.
Robert Pavlis writes a very fine blog about gardening myths. He has been doing a series on soil organisms which includes references to flagrant claims in advertisements for organic fertilisers being beneficial because they encourage bacteria. He gives many excellent references to real scientific research to support his conclusions. You might like to read them.
Am I just out of touch or are Canadian and US citizens more gullible than we are? Perhaps their advertising is even more cynical than our own. Apparently over the pond you can buy bacteria to add to your soil! How pointless! No real gardener would use them.

This is a very useful bacteria that you can buy in France. It is not a soil bacteria but is a very effective bacterial disease of caterpillars that you can spray on your brassicas. I will pluck up courage to write about it one day!

Significance of soil bacteria
There are many ways to convey the magnitude of the presence of soil bacteria. Not only are they not very accurate they are likely to change with the next piece of research. I can’t quite believe that the mathematical progression of a single bacteria surging to 16 million in 24 hours is actually true! I find it easier to believe that the weight of bacteria in an acre of typical soil weigh as much as two cows! Of course if you go deeper, to perhaps more than a mile you, will find that half of the world’s biomass is bacterial! 
I do find it impressive that there might be a billion bacteria in a single gram of soil and that hundreds of thousands may be different species. 

The real message to a gardener is that there is a huge number of soil bacteria and they reproduce very quickly and their numbers dependent on changing conditions may grow or decline by several orders of magnitude within just a few hours. So much for any thought of adding a few from a packet - and anyway they may not be the right ones!

Certain bacteria are essential for soil fertility. In contrast a few are actually plant diseases. 
There are two significant bacterial diseases of cherry - leaf spot and bacterial canker

One of the most significant bacterial pathogens is agrobacterium which can induce galls and tumours on plants by horizontal gene transfer!

Most of the huge number of bacteria in a soil are quite insignificant to the gardener. Perhaps this is untrue in that the good, bad and indifferent may compete together for resources in biocidal combat. Some that seemingly have no known useful function may do so in the future.

Examples of factors that massively and speedily effect bacterial numbers are soil temperature, aeration, drainage, pH, availability of water and carbonaceous material. 

Bacterial soil superstars
These are the ones you will learn about if you study soil science.

Ammonifying bacteria. These convert organic forms of nitrogen into inorganic ammonium. This fundamental process in the nitrogen cycle is known as mineralization. 

Nitrifying bacteria. These convert inorganic ammonium in a two stage process, first to nitrite and then on to nitrate.

Symbiotic nitrogen fixing bacteria. Examples are those that live in nodules on legume roots and enable the conversion of nitrogen gas into organic chemicals. They are one of the very few examples when it is sometimes worthwhile - via commercial seed treatment - to inoculate specific strains of bacteria into the soil

Free living nitrogen fixing bacteria act directly in the soil. They are not very significant in UK soils.

Denitrifying bacteria. These are associated with anaerobic waterlogged conditions and lead to polluting loss of nitrogenous gases to the atmosphere.

Thermophilic bacteria. These bacteria of decay can heat up a compost heap. Although desirable, they are not essential to the composting process.

Actinomycetes. These bacteria have characteristics of fungi - such as reproducing from spores. They are significant in the breakdown of tough chemicals such as lignin and cellulose. 

Cyanobacteria. These green photosynthesising and nitrogen fixing bacteria are of huge worldwide significance but are not commonly found in temperate soils. They also have an almost unique ability to ‘mop up’ high levels of nitrate from water. One to watch for the future!

Relevance of bacteria to gardening practice

Soil cultivation will aerate the soil, but not necessarily in the way you might wish. Aerobic bacteria will increase, which in turn increases the speed of breakdown of organic matter. For the gardener this conflicts the competing needs of release of nutrients and maintaining organic resource.
The other side of this coin is that the better pattern of oxygenation which results from minimum cultivation will usually lead to the highest bacterial populations yet retaining higher levels of organic matter.

Liming, fertilising  and manuring practice all effect bacterial action

Poor drainage leads to an increase in undesirable anaerobic bacteria

Good composting occurs when bacterial action is maintained by heat retention, sufficient nitrogen and application of lime.

Because temperatures have a fundamental effect on bacterial action, soil in winter will have next to no nitrate available to plants. In contrast a nitrate analysis in late summer will show greatly enhanced levels. 

It’s more important how fertiliser practice is effected by bacteria rather than how fertiliser practice effects bacteria!

A few less well known facts about soil bacteria

Thirty years ago growers would sometimes apply the systemic fungicide called Benlate as a soil drench. It was noticed each time it was used that its action diminished. It turned out that a soil bacteria could use the fungicide as a food and with each application the bacterial population population increased and gobbled up the fungicide.

In a similar vein, growers and farmers were permitted to dispose of washed out empty pesticide containers by burial. It was recommended that the holes were not too deep. Soil bacteria that degrade the chemical residues are far more numerous near the surface.

Thirty years ago it was routine practice for glasshouse growers to steam sterilise the soil. This was  primarily for soil pest and disease control. Most, but not all of the bacteria were also killed. In the absence of competition the first bacteria to colonise back - and without competition in greater numbers than before - were those bacteria that release soluble nutrients. The effect of planting in still warm soil with an increasing level of available nutrients over the first few weeks of the crop was highly valued by growers.

And I am sorry to spoil the party, but my beloved glyphosate has biocidal properties! In terms of how I use this herbicide the effect is insignificant!

On the brighter side it is now starting to be thought that a child’s exposure to soil and other outdoor bacteria greatly reduce future sensitivity to allergies.

A story about bacteria from my friend Peter Williams

Microbiologist and maestro gardener Peter Williams played a very significant part in the greening of Northern coal mining slag heaps thirty years ago.
An important aspect of their restoration was the use of huge quantities of lime. A bacteria called thiobacillus acts on iron pyrites in the coal waste to release sulphates which form sulphuric acid. The acidity of the slag can become as low as a a remarkable pH 1.5! The most acid you will ever find a real soil is a very rare pH 3.5.
Peter tells me that in the reclamation they used lime at 200 ton per acre every two years. He remarked that a farmer might use lime at 10 tons per acre once in his lifetime! When they applied lime the colliery waste fizzed!

He went on to tell me that on a similar site in Wales when land engineers used concrete drains, to their surprise and consternation within a year they had dissolved away.

I hope the above arguments help to persuade you that gardeners should carry on with good gardening and forget about the bacteria. They will look after themselves!

Yesterday morning I discussed this post with Peter W. and the futility off adding bacteria to the soil. The conversation turned to adding mycorrhizal fungal spores from a packet! Mycorrhiza are of course fungi and not bacteria. As I have posted before mycorrhiza are highly beneficial and sometimes essential. I have previously shown doubt about adding them from a packet. 

Peter is a fine microbiologist with a special interest in mycorrhiza. He has been talking to colleagues even more knowledgable about fungi than he! After our conversation this morning I now feel emboldened to offer our opinion that adding spores from a packet is a complete waste of time. 

Monday 20 April 2015

Blogger Page Views milestone for the No Dig Gardener!

Roger has a little Google Page View counter on the No Dig Gardener blog, just as an indicator for him to see if he gets any visitors. He is quite obsessed with both the counter and Google Analytics!

First, let me apologise to all the gardeners who read Roger’s blog. This post is not about gardening, although I’m sure all you other bloggers out there will understand.

I’m Cathi – Roger’s neighbor and long-suffering resident blog adviser! Roger is away on one of his jaunts to see family in France at the moment, and all the excitement has happened in his absence. He’ll be so disappointed!

The Page View counter reached half a million on Sunday morning!

Reaching the half a million page view mark

That is 500 000 pages looked at! His very first blog was published 26th June 2012. I find it more than a little amusing that the no dig gardener’s half million was reached on 19th April 2015 with this active pagewhich was published 1st November 2012! It’s a post about digging – oh, the irony!

Still, it was ever so exciting watching the counter hit half a million.

…and I just can’t resist posting this picture!

Sunday 12 April 2015

Why does my new tree grow so slowly?

Trees and shrubs can be inhibited by grass and weed!

There are many reasons why woody plants fail to make healthy new growth and sometimes die! Causes are from the common place such as planting too deeply, failing to water or watering too often to the totally bizarre, such as strangulation and urination. Today I have only one focus: competition from grass.

Grassing up to the base of young trees stifles their growth.
The stunting of tree growth can be quite extreme and sometimes a woody plant fails to grow at all and may be more susceptible to pest and disease. Not always, some very vigorous plants such as the Norway maple might not miss a stride.

This vigorous Cedrus atlantica glauca tolerates the poor winter aeration in my deep wet soil and thrives

As a tree eventually achieves some stature it starts to outgrow inhibiting grass. 
In traditional fruit growing practice, reduction of vigour and promotion of fruiting was achieved by grassing down orchards. Such an effect might be an advantage to gardeners when in later years a tree threatens to outgrow its position.

My Acer griseum has made very little growth in twelve years
I often see inhibition of tree and shrub growth as a result of grass competition and have experienced it myself. Numerous trials by the landscaping industry have demonstrated dramatic effects. After several years in soil clear of vegetation a young tree might achieve double or treble the height of its grassed down neighbour. 
Sometimes gardeners plant shrubs in a lawn and they often die for lack of summer water.

To my amazement I have witnessed arboreta that don’t understand this phenomenon. I have seen young trees just standing still for years in coarse weed or grass. I think that their green credentials do not permit them to get out the knapsack and underspray.

Although grassed to the base I sometimes take out just a little grass to facilitate mowing
It’s all about competition
Horticultural students are taught weeds compete for light, water and nutrients. We can discount light unless very small saplings are planted in very rough grass. Shortage of tree nutrients is significant but it is lack of water that makes the real difference.

Many gardeners are surprised how most tree roots grow in the top 30cm. That is the  most fertile place in respect of air and availability of nutrients. A significant proportion of rainfall comes in small doses and just wets the surface. Shallow roots get first bite of the cherry.
Grass is a past master at making strong surface roots. It has evolved that way to survive on savannah. It is a moot point how the deeper roots made by un-mown taller grass compare with the dense matted roots of mown grass. Mown grass is usually the worst competitor because constant mowing keeps it constantly green and transpiring compared with tired old leaves on uncut plants. Dead grass might even give temporary benefit to the trees by mulching!

A particular problem of tall un-mown grass is at the base of a tree trunk when wet conditions prevail and wet leaves and humidity facilitates fungal infection.

I had intended to speculate about allelopathy where one plant chemically inhibits another. I knew that couch grass produces organic toxins that act as natural herbicides. I wondered whether such an effect might occur with other grasses. I found this site which claims allelopathy has a huge inhibiting effect on trees. Not all the allelopathic grasses quoted are relevant to UK lawns! 
Kentucky bluegrass, red fescue, perennial ryegrass, Bermuda, and bahia grass all produce toxins. As much as 50% inhibition has been suggested. I have no idea how such a figure is derived!

Another danger is when closely grassed  trees are damaged by mowers.

So where do trees grow best?
Trials have shown that they establish best in soils clear of vegetation. After planting such soil is best left undisturbed and kept weed free by shallow hoeing, hand weeding or spraying. The very best results of all are when weed free soil has a thick mulch. Most research into this has used materials such as bark mulch. If appropriate, don’t overlook loose gravel or stone.
In real gardens you will want to underplant the trees with plants!

This tuberous corydalis is only above ground for ten weeks in winter and  provides zero competition.

Winter bulbs generally thrive under deciduous trees
So what can a gardener do to grow trees in the lawn?
Short of avoiding grass altogether to plant in clear soil circles is the usual solution. A meter or so diameter, although not perfect, will make a huge difference for the first few years. There will come a time that you can dispense with the circles. (and any ugly  stakes - but that is another story).

Whoops - I have just noticed the ugly stake. As Cathi’s gardener I need to remove it. These trees have sprayed out circles to facilitate safe mowing. I have already removed several decapitating branches to protect Cathi when she charges round on her ride-on mower!

I hate seeing trees planted in excavated depressions with deep edges that catch all the litter. Worse, if winter drainage is poor the sunken soil catches the rain. Best for your plants to be level with the lawn or in wet gardens slightly raised.

Personally if I want to plant a tree in grass I kill out the circles with glyphosate and plant direct into the lovely fibre-rich soil. I cringe when I see gardeners moving good turf - their very best soil - to plant trees!

What about ornamental borders under trees?
It’s probably not a good idea to grow grass under a grove of  trees. You will get a load of green moss as a result of their shade!
Most of we gardeners will wish to grow mixed plantings of ornamental plants. To varying degrees such plants will compete for the trees’ water but dehydration will be much less than that caused by a lawn. 
For most of us as trees become well established our new worry will be that the trees will dehydrate our plants!

In terms of a beautiful garden most of us will opt for tree plantings with a ‘natural’ looking understory of nice plants.

Most of my own trees are planted in mixed borders

A couple of caveats
Wise gardening words are often redundant in unusual circumstances. My own garden is a deep coarse silt  - I have previously wrongly described it as fine sand - overlying sticky clay about two metres down. My perched water table ensures deep roots can always find water. My own trees are grassed up to their bases. It was a surprise how much the grass suppressed my Acer griseum and ginkgo but all my other trees have grown very well.

My advice to plant trees in clean soil applies to climates like here in the UK where dry periods in summer are rather frequent. My advice will not apply in places with high all year round rainfall. I saw a shrub border in Eire and another in Costa Rica where the complete planting was in mown grass and grew very well.

A tree planting scheme remembered
The promotion logo was …
‘Plant a tree in 73’
The next year it became…
‘Plant some more in 74’
A wag added…
‘None alive in 75’

The cynic had noted that the public were encouraged to plant trees in the countryside without any indication that without after care their chances of survival were small.
I saw many trees after planting invaded by coarse grass, ground elder, bindweed and all manner of dehydrating vegetation. No wonder many died or at best stood still for many years.

Bolton Percy Parish Council were informed that they would receive fifteen trees the following week. A planting committee was immediately convened. As the only horticulturist I was made chairman. In practice the committee was never quorate and I chose the sites and did the planting and all subsequent maintenance. 
The trees that arrived were a curious selection. No wonder the nursery industry loved the scheme, they could sell all their surplus. It was proclaimed that each tree would have a ‘tree preservation order’. How stupid - any administration and preparation of plans would take a much greater time than planting and maintenance. I was not only too lazy I did not want to saddle people with future trees that might be in the wrong place, outgrow their space or even prove to be eyesores when perhaps not very healthy. The only plan of the whereabouts of these trees is in my head!

It is very difficult to suddenly find places for extra trees in a well wooded country village. My choices were rather desperate. It was the year before I started to maintain the then rather wild Bolton Percy Cemetery. Five trees were planted there. Twenty years later I was rather relieved when three by then large Sorbus aria, were chopped down when part of the old churchyard wall needed rebuilding. Every time I make my monthly maintenance visit I curse myself for the deep shade under a wretched huge sycamore I planted. On the other hand a beautiful Amelanchier canadensis in the parish room yard has thrived and produced beautiful blossom and autumn colour for the past forty years.
Last month I took it into my head to see how many trees have survived. I was pleased to find ten including a fine copper beech that will grace the village for the next hundred years.

Planted in 1973 this copper beech is starting to make a fine tree. If you look carefully through it you will see another tree planted at the same time across the road. Sadly it is being strangled by ivy

Now worthy of a tree preservation order - hint to Parish council

In these links I discuss the theory of water conservation by mulching and dehydration by planting.

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