Published: 17 July 2013
The Cultivation of Today's Plants
Renowned horticulturalist Peter Thoday looks at the journey taken by the cultivated plants that we recognise today.
Some gardeners love novelty and they search the pages of their seed and plant catalogues for new cultivars. Others are equally attracted to the conservation of old favourites, be they fruits, flowers or vegetables; they applaud the work of the NCCPG whose efforts have been so successful in keeping old kinds available. But regardless of whether you are an enthusiast for old or new cultivated forms they are more than likely to have arisen as a result of either a mutation or hybridisation.
 
In the 19th century one school of thought, whose most famous exponent was the French scientist  Jean-Baptiste de Monet Lamarck, believed that changes to an individual plant resulting from the improved conditions created by cultivation, could be passed on to its offspring; so the cabbage nearest to the compost would produce seedlings of a greater than usual size. 
 
Well evolutionary change based on that theory was disproved but to get to the start of how change really comes about requires a surprisingly long trip back in time. Back in fact to the start of cultivation some eleven thousand years ago; to the time when humankind started to change from a hunter gather lifestyle to become man, or more correctly, woman the cultivator.
 
This massively significant event occurred independently in at least six widely spaced locations, North China, the Indus Valley, Central America, the foothills of the Andes and most significant for we Europeans, the Middle East, in the region known as the Fertile Crescent. Of course these first cultivators had only their local wild plants to grow so it is no surprise that the plants they had traditionally collected became their first crops. What I think is remarkable is that their selections have stood the test of time to remain today’s staples, among them the wheat’s and barley.



As the new lifestyle spread across the region and into South East Europe more plants were added to the grower’s repertoire, kinds we would immediately recognise from our current orchards and the vegetable gardens. Well maybe recognise them if we looked as hard as we have to when identifying a wild flower from a description in a flora. In every case the first sowings would have looked just as their wild progenitors. They produced a harvest that might seem to us to be of little use except as additional bulk for the pottage pot. Indeed that was the destination of most vegetables just as it had been for centuries when they were collected from the wild. But then came the big surprise, over the first century or so something unprecedented happened. Plants in the care of the cultivators started to change in ways that benefited the growers. 

Charles Darwin
Charles Darwin suggested that such changes must have been due either to what he called unconscious or methodical selection.  Today most people think it was probably some of each, part due to the sharp eyes of the growers and part evolution by “natural” selection, only in this case “natural” applied to the environmental conditions the plants encountered under cultivation. It’s a process that is still at work whenever we introduce a wild flower into our gardens or when a weed becomes resistant to a herbicide.
 
These qualities came to prominence after the plants entered cultivation but some of the variations in the gene pool that lay behind them had probably been around for a long time while others were new mutations.
 
The mutations that were “unconsciously” selected helped the plants to adapt to life under cultivation while those “methodically” selected by the growers affected such things as the overall size, form or chemical makeup of the plant or, quite often, only the bits we use, what is now known as the harvest organs.
 
The pansy is a good example of an overall increase in the size of virtually every part of the plant, while weeping ash, prostrate rosemary, fastigiate hornbeam and bush courgettes all show changes to their habit of growth.

Edible crops at Hampton Court Palace show earlier this year.
Among the outstanding examples of the massive development in the size and/or shape of harvest organs are pumpkin fruits, cauliflower curds and parsnip and carrot roots.
 
It is not only morphology and anatomy that have changed, many mutation derived cultivars show altered chemical composition. There has been an increase in sugar content in many fruits and most famously in sugar beet while we have benefited from a reduction in acidity in apples and pineapples. Poisons have gone from beans and cassava. The chemicals that give flowers, fruits and  some leaves their colour has changed producing yellow tomatoes, the red leaves of some Acers and the rainbow of colours of our flowers such as petunias and zinnias. In contrast white flowered mutants, many of which were collected and cultivated hundreds of years ago, suffered a loss of pigment. 

In the case of the wild cabbage the early changes resulted first in the leaves that grow from the bud in the centre of the rosette remaining packed together to form a heart.  Then over the next thousand years a remarkable succession of distinct forms appeared giving us the Brussels sprout, cauliflower, broccoli, kohl-rabi and various forms of kale.



Such changes may seem both unlikely and strange to most of us. Our casual view of nature suggests that all wild flowers of a kind are identical. In fact they are not, as the Reverend William Wilks realised as he walked round his rural parish of Shirley. The result of his patient observation, diligent seed collecting and many generations of selection and crossing produced the colourful display we know as Shirley poppies. The poppy story is a great example of sharp eyes finding variation in stands of a wild species. It is an approach that still goes on in the wild, the nursery and the garden. It is the origin of what used to be known by the helpful title of “improved forms” although the rules of nomenclature now require us to identify each as a separate cultivar.    
 
So much for mutations, but surely when we turn to hybrids as a source of new forms we must be talking of recent developments? Well it’s true the first deliberate hybrid between two plant species was made in 1717 by the nurseryman Thomas Fairchild but our bread wheat that now feeds half the world first occurred back in the fertile crescent some nine thousand years ago!
 
Its creation was a chance act of nature but one that was noticed, saved and perpetuated by our skilled forebears. Such naturally occurring hybrids, be they hundreds or even thousands of years old were in themselves, in their time and from our human point of view, great steps forward, but it is their role as the foundation of future cultivars that has proved to be of even greater long term importance. In successive generations their nixed blood [their gene pool] combined in novel ways to produce even more useful forms.  A good example from the flower garden of a hybrid being a springboard for change and diversity lies at the heart of the auriculas, those plants so greatly loved by gardeners in the 18th & 19th  centuries  We now know that the reason that the early enthusiasts, known as “fanciers” or “florists”, were able to achieve such a wide range of flower colours and forms from among their seedlings was that, although everyone at the time thought that the plant that entered cultivation was the alpine beauty Primula auricula it was in fact a natural hybrid between this species and Primula hirsuta, a genetic mix that kick started a flood of beauty.               
 
Centuries before the Reverent Shirley’s vicarage garden was pressed into service as a breeding ground for poppies, gardeners were collecting the very occasional specimens of wild herbaceous and woody perennials that had variegated foliage or double flowers. The large majority of such forms did not, or in the case of sterile double forms, could not produce similar offspring from seed. These one off somatic mutations, as they are known, had to be propagated by layers, cuttings or grafting all techniques that have been practiced for over 2000 years. 
 
The gardeners of Ancient Greece used the same methods of vegetative propagation for their much loved vines and olives as they knew that seedlings could not be trusted to produce the quality of produce of their parents.
 
Of course a short note like this can only scratch the surface of the story of our discovery of cultivation and the subsequent appearance and perpetuation of the multitude of the plants we grow. I hope I have persuaded some readers to think a little more about how it is that in both garden and farm we find ourselves surrounded by what may be loosely described as “man made” plants.
 
Peter Thoday

About the Author

Peter Thoday
Peter Thoday is known as the presenter of the brilliant television series called ‘The Victorian Kitchen Garden’. Since those days he has been lecturer at Bath University and more recently horticultural advisor and consultant to many garden projects, including The Lost Gardens of Heligan and The Eden Project.
 
As an agronomist Peter Thoday is an international authority on many horticultural subjects, including the history of plant development. Both ornamental and edible species come under his scrutiny and his extensive knowledge, and words of wisdom, are sort after by both academics and practicing horticulturists. 



The above editorial gives an introduction to his two books. The first is called “Two Blades of Grass” and looks at the fascinating history of the development of cultivated crops since the days of early humans.  Peter’s second book is called “Cultivar – The Story of Man-Made Plants” and takes an in-depth look at how mankind has manipulated plants to our own advantage since the early days of cultivation.
The Gardening Times will be reviewing Peter Today’s books in the coming weeks with details of where to purchase them.  
 
If readers have any thoughts about this fascinating subject please send your thoughts to us by email: readers@thegardeningtimes.com
Reported by Peter Thoday  
   
 

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