Saturday, 29 February 2020

Companion planting, is it just tosh or is there something in it?

By all means mix plants together and avoid monoculture but read on...

It is all very complex
Companion planting is usually associated with pest control that arises from planting two or more different plant subjects together. The concept can be extended to the idea of plants being mutually beneficial to each other in other ways such as combined yield increase or giving each other a protected environment.
Both ideas can be flawed and in particular the first concept is supported by little evidence, gross exaggeration and wishful thinking and endlessly repeated myths such that companion plants need to be strongly scented. 

Except there are exceptions. Nothing in the fascinating plant world is simple.

As to the second concept, plant yield is usually limited by mutual competition for such as  available light and water. Growing for example a root crop among a leaf crop leads to lower combined yields than when the plants were grown separately.

I suggest that most companion planting arising from dedicated pairings or perhaps more commonly a ‘deterrent plant’ within a crop are a waste of time either because they are  completely ineffective or have only marginal impact which in normal practice is useless.

Take the highly popular belief that marigolds deter whitefly on such as tomatoes. Well they actually do - but not well enough. For me one whitefly is too many - on a plant like tomato which is so susceptible to glasshouse whitefly (indoors and out) a single whitefly soon becomes an infestation. Those who declare complete success with marigolds as a deterrent are probably good growers who do not insist on overwintering whitefly in their heated greenhouses on such as pelargoniums and do not introduce it into their gardens in the first place in Summer on such as their greenhouse propagated french beans. Without any companion planting I have not suffered from whitefly in twenty years. I would go so far to say that  my tomatoes have not encountered a single whitefly in that time (As opposed to brassica whitefly on my sprouts which is a different story)

You might be wondering why I have apparently destroyed my case by quoting one of the very few pairings, whitefly and marigolds where there is actually some deterrent effect! Indeed Newcastle University have extracted limonace (also the main oil in orange peel), the chemical actually responsible and have suggested it might be applied as a spray. To my mind spraying would be the kiss of death to the idea bearing in mind how gardeners seem to regard any spray as the work of the devil!

My example stands out as a kind of success story among other rather more useless popular pairings and my point is that a gardener has better things do than companion planting - except he might get pleasure from his illusions and might even like marigolds in his carrots. Actually marigolds are a fascinating plant and do produce root secretions toxic to eelworms and for certain plants in certain climates they might be useful - but in your own garden? Forget it.

I remember a bright intelligent student totally imbued with organic notions. He enlivened my lectures - not an easy task. His ‘plot project’ endeavoured to demonstrate the success of companion planting. With the best will in the the world we could not discern the benefits he purported to show. (But he won the plot prize)

I am indebted to Robert Pavlis whose latest post shines further light on companion planting. He shares much of my scepticism  and his post
specifically rubbishes the idea that it is scented plants that work these pest deterrent wonders. But first read this…

Evolved relationships between pathogens and plants
Is companion planting a waste of time?
Gardeners may feel that modern research which shows how plants communicate one with another -  often by scent - gives strength to the belief that scented plants confuse pest predators in companion planting. In fact it is very specific pheromones by which plants can communicate in closely evolved relationships where for example they warn one another about the presence of pests and consequently produce chemicals antagonistic to them. It does not follow that because plants have a strong scent they do the same. Our own senses do not discern a  plant’s subtle communications.
You might imagine that measures of natural plant self protection bear some resemblance to precise controls required by the gardener. Not so, there are subtle balances between potential pathogen and host. After all plant priority is to set a lot of fertile seed. It is not a priority to kill every last pest - that is too expensive to the plant’s resources.

To go further when you look at the plant world there is a spectrum between plants and potential predators which runs between complete symbiosis to total destruction. It is sometimes not clear whether an organism is an enemy or friend.
Why is it that such pests as red spider mite or whitefly cosy up to certain plants in abundance and yet other plants hardly suffer from them at all. Indeed one researcher asked why is it that most pests have restricted hosts and only attack vulnerable species? Is there anything in it for the so called victim?
It can all be represented as evolutionary combat.

It might be taking things a bit far to speculate why a plant might allow itself to tolerate a particular pest. A researcher suggested that aphids could be good for a plant in the wild that is in infertile conditions. Aphids drop honeydew which can stimulate nitrogen fixation in the soil. The plant effectively gives up sugar to achieve more nitrogen and thereby maximise its seed production.

My Solomon's seal missed the sawfly this year
I myself wonder why solomon's seal allows sawfly to decimate it so severely year upon year? Could it be that in late Spring it has completed its life cycle and hived away in its thick roots ample resources? It just might be a service for the tough leathery leaves to be chomped up into manure.

Why do brussel sprouts abandon their green leaves on old stems when attacked severely by fungus disease in late Autumn and yet the sprouts and the plant tops stay green? Is it saving its resources to fight the real battle?

You might very well ask what is all this to do with companion planting?
I am not really sure myself! It does illustrate that plant/ pest relations are complicated and most companion plantings are too simplistic and that nature’s aims are not the same as our own.

(If at this point I might put in a promotion for my next but one post. It is about symbiosis when organisms  evolve in harmony. New thinking is that symbiosis is a prime driver of evolution right down to genome level. Those of you have followed my series on evolution might wish to read it)

The appropriate/inappropriate pest landing theory

Thank you Robert Pavlis for reporting this elegant study at Horticulture Research International, Wellsbourne UK . I applaud this prestigious institute which in a previous guise was the National Vegetable Research Station. If you grow your vegetables in anything like a modern away you can be sure that their innovations play a major part.
In a series of elegant experiments they demonstrated that flying vegetable pests having generally identified the area of their host crop by scent from the air and are only attracted down to the ground by the colour green. Any green plant would do and even green coloured paper attracted the pest. They planted a wide range of potential companion plants around vegetables crops and all that were green attracted the pest. Any plants that were any other colour did not attract the pest.
The pest detects on alighting whether anything green is the appropriate host. If not it tries again on a nearby green plant. The more ‘false starts’ the less eggs will be laid. It was shown that any green ‘companion plant’ fulfilled this function. Conventional coloured scented ‘herbs’ performed poorly. There were several examples of vegetables that had lower pest loads when they had  green companions such as clover!

This might lead you to the correct conclusion that such as ground cover and weeds(!) would both satisfy this deterrent effect!
Hang on! Weeds might decimate your crop far more than pests and ground cover might reduce yields by competing for water. Take care not to draw the wrong conclusions from new discoveries!

Companion plants as a lure
I knew a dutch commercial grower of tomatoes who used a few pots of french beans in his glasshouse as a trap for whitefly. Each week he would remove the infected pots and replace them.
I have not time to discuss this principle today but will merely quote Robert Pavlis’s dry comment that his neighbours are only too welcome to plant them

Grow a wide range plants and avoid monoculture

Although I have been sceptical today about targeted companion planting I must hold true to my conviction that growing a wide range of plants in your garden is a fundamental arm of cultural pest control where diversity provides a myriad of habitats for predators of pests. In contrast farmers and commercial growers are stuck with large monocultures and find the need to regularly spray


Robert Pavlis writes about companion planting

Peter William's  article on natural planting

Tuesday, 11 February 2020

Stress from the floods

Roger and Cathi's garden. It got much worse than this
Drain Strain September 2019
As I write this we have no idea how it will end. A huge lake has invaded our garden. It might be only 30 cm deep but it covers more than a hectare. It covers half of Cathi’s garden and continues on over her fields. Its total volume must be more than a million litres.
Each time in rains yet again the lake’s level rises by more than the rainfall. A centimetre of rain brings a rise of rather more. Each dry day there is no perceptible fall in the level. We have had a pump going that takes out thousands of litres an hour. I makes no difference. Imagine  emptying your bath at a cupful a day- or perhaps even by a thimble?
As I write at the moment I cannot bare to predict the harm to my garden. At present a fifth under water a further rise of  40cm will threaten our house. Already Cathi’s barn is under water. Every morning she wades across the mud to feed her old rhea stranded and isolated on the far bank.
There is still ahead of us a Winter of wet and little evaporation.
I cannot bare at this stage to elaborate on the measures we are taking to provide drainage.

It looks spectacular at times

Drainage theory
Let me step back to describe the fundamental principles.
Most gardeners are familiar with the problems when water stands and cannot penetrate through. The problem is usually puddling or compaction and gardeners often try to improve absorption by adding gritty materials and busting compaction.
This is not relevant to me as my soil is almost pure sand. Unfortunately  two metres down it is pure clay where further penetration is almost impossible.
A route for surplus water
This is achieved by buried drainage tubes and ditches. On a very small scale perhaps rubble drains. The problem of course is there must be places for pipes and ditches to go.
Water received from higher land
This can be very much more than the actual rain that falls on your land. We have that in diamonds  and are surrounded by higher land on three sides to the garden.
How long will things survive underwater?
About half my garden has been underwater
February 2020 The black dog descends
I don’t just mean the black stinking mess our garden became after six months of standing water but also the dark depression that crept up on me to the point that I am now on medication against acute anxiety. Brenda too struggles to hold us together. Its worse for Cathi next door. For months she waded every day across foot deep ever muddying water to feed her rhea stranded on the far side. Her shed is flooded and birds are trapped high in her henhouse. The ducks love it as each morning they swim outside. She struggles to keep her rescue hedgehogs thriving and cart out extra food to supplement the grass for her soay sheep.
It is only now I can bear to tell you about our watery nightmare. It’s not over yet but the end is nye. You might have noticed my posts have appeared less frequently recently. I have almost run through my stock and must write some more. I have just not felt up to it. Several further posts will be on the implications of this watery theme.

Things got worse after my first paragraph written six months ago. Our problem is that our gardens exist in what in Winter is a great big wet hole. Cathi and our own flooding has coalesced into a seven acre lake.
As we all know it just kept on raining last Autumn. In a two month period we had the rain for an average year.

Searching for the drain in the dry top part of the garden.
So much for no dig gardening!

Hitherto we have been dependent on a huge fourteen inch bore drain laid in 1940 by War Agriculture when constructing the then Melbourne airfield. It has become partially blocked over such long time. It runs down into the three foot slope to the top of our garden.
It goes under a fairly busy road at a depth of seven feet - and runs away to lower fields below

The horror of finding the under road blockage
We of course with the help of drainage experts dried to clear the drains. Our world came to an end when they found that re-metalling the road several years ago had almost completely smashed the drains.That is the only route to take the water away

Everyone told us being under the road made it the council’s responsibility!
Ever tried to get speedy work from a council whose maps show no drains at all! Cash strapped councils don’t do these things without prodding and ‘legislation’ and considerable time - which we did not have. We were told of a case where a council was successfully sued but the litigant was NOT awarded costs - more in lawyers fees than paying yourself.
We have asked a reputable contractor to do the work which as I write is delayed by administration!

A faltering step forward

By the time the lake had extended to seven acres Peter Williams and a local farmer John Rowbotham came up with a short term solution. John has a drain that crosses under the road two fields away from our flooded area and it has spare capacity. The farmer who owns the intermediate field (itself thoroughly saturated) kindly agreed for a drain to be cut across his land. Local drainage genius Robert Hunt braved the bog to cut in a three inch drain that leads into a temporary ditch that gives the water a route out. A ‘full pipe’ removes thousands of gallons an hour and yet it will still take a month to clear the water (And that assumes no more rain - some hope with a huge storm predicted for tomorrow)

The machine that laid the drains was very speedy and Robert managed to not get stuck in the bog
Temporary ditch runs water to the drain
After three weeks the flooded half of my garden is starting to reappear. Not so for Cathi where the water is much deeper. Heaven knows how many of my thousands of plants have been killed after up to five months under water.
I will be keeping you posted!

Six months ago - much worse was to follow in Cathi's garden
The very next day from writing the above it rained more than two inches - put us back at least two weeks
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