The weeds are having a tough time of it too
Post categories: weeds
| 07:00 UK time, Friday, 19 August 2011
Charles Robert Darwin (Photo: HO/AFP/Getty Images)
I was asked recently if gardening at , home of 40 years, gave me a "more philosophical outlook on weeds". As strange as it sounds, some parts of the garden wouldn't be complete without them.
Darwin's 1857 'weed garden' or'seedling mortality' experiment as it is also known, was one of the many garden experiments he carried out at Down. In particular, it helped illustrate an important point in the third chapter of On the Origin of Species By Means of Natural Selection.
In introducing the world to his theory of evolution by Natural Selection, Darwin had to demonstrate the pressures that plants are under, and how these pressures - a universal 'struggle for existence' - were an essential part of the ongoing process that eventually gave rise to the wide diversity of life on earth.
Cold, drought, grazing, pests and diseases, competition from other plants - including closely related species and even individuals within their own species: all of these pressures fuel the process of natural selection in this experiment.
Slight genetic variations in the seedlings give some of them an advantage over the others in this particular environment. These well adapted few - not just the biggest or the strongest seedlings - are able to survive these pressures long enough to flower and fruit, and to pass on their advantage to some of their progeny, which continues this refinement generation by generation.
These changes can add up so greatly over time, that they give rise to new species of the most suitable plant for their present environment - even if we gardeners consider it a weed.
The Weed Garden at Down House
Since the garden has been restored by , this simple experiment has been recreated each year from spring, following Darwin's description.
'On a piece of ground 3 ft long and 2 ft wide, dug and cleared, and where there could be no choking from other plants, I marked all the seedlings of our native weeds as they came up, and out of the 357 no less than 295 were destroyed, chiefly by slugs and insects' (On the Origin of Species chapter III).
Marking the seedlings with a short piece of wire, just as Darwin did, and keeping a regular tally through the season, we've found that on average only one in six weed seedlings survive until they can reproduce. Reassuringly, the same ratio of survival that Darwin found continues at Down to this day.
So what has this told me? No matter how much of a struggle a gardener's non-stop battle against weeds can be, at Down House, nature is helping out by killing off the 'least suitable' 83% of weeds, often before we even get to them.
Perhaps I should be proud in knowing that the weeds elsewhere in the garden, those that we end up hoeing down, those not lucky enough to be growing in the experiment plot, were descended from the 'best of the best'. Possibly from an elite handful of weeds that once upon a time slipped by Darwin's own gardeners, Brooks and Lettington.
A botanical rogue's gallery honed by generations of natural selection but not quite evolved enough at the moment, thank goodness, to make it past a well sharpened hoe.
Rowan Blaik is the head gardener at Down House.
Comment number 1.
At 19th Aug 2011, Dan Martin wrote:Great blog post, and what a good place to work. For some reason I thought that all weeds were 'super' plants that seemed to be resilient to everything that attacks my veg. I will try to look on them a little more fondly, now knowing that less than a fifth will survive. Although I'm sure the overwhelming colony of snails in my garden are definitely more interested in eating the broccoli and brussel sprout leaves than the weeds.
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Comment number 2.
At 21st Aug 2011, hereisabee wrote:Darwin published the The Origin of Species... in 1859, ten years later a Buddleia was discoved in China by the French missionary Pierre David that has since borne his name. However many of the early introductions of the plant were thought unsatisfactory (although probalbly in terms of flower). Since then this plant (Buddleia davidii) has sought out every nook and cranny in the urban environmeant, it would be interesting to compare it's make up to wild plants in China to see if our weed has in-deed evolved?
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Comment number 3.
At 25th Aug 2011, Papa Nopsis wrote:Although I have spent more heavy man hours working on my garden than ever before, there are also more weeds than ever before! A wholesome bed of poppies just does not like to be weeded without losing the poppies as well, unless you choose broad leafed varieties.
After digging over the whole garden, when flowering and propagating weeds arrive in profusion you suddenly begin to realize the value of the weed!
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