Darwin’s Weed Garden
Darwin’s garden was a site of scientific experiment. He cleared a small patch of ground to watch the progress of emerging weeds over a period of time. He was surprised at how many seedlings came up and was even more surprised at how few survived. He cleared the ground in order that no effects could take place by existing plants or weeds crowding out others, and he meticulously observed number, variety, size etc of different weeds and wild flowers that grew there.
Darwin recorded this experiment under the heading ‘Weed Garden’ in his Experimental book. Selecting a small plot of land in the orchard protected from large animals, he cleared it of all perennials in January 1857. Here are extracts from his notebook and letters indicating its development.
Experimental Notebook – March 1857
Weed garden – Old shrubbery & then Strawberry neglected Bed. Piece of foul (but not very foul judging from rest) ground in Orchard, which had been (Shrubbery and then for a year or two) strawberry Bed— in size 36 inches by 24 inches.—(protected from large animals) Dug in January & cleared of all perennials— Early in March seeds began to spring up: marked each daily.
Letter from Charles Darwin to Joseph Hooker,21 March 1857
I am amusing myself with several little experiments; I have now got a little weed garden and am marking each seedling as it appears, to see at what time of life they suffer most
Experimental Notebook
Darwin’s garden was a site of scientific experiment. He cleared a small patch of ground to watch the progress of emerging weeds over a period of time. He was surprised at how many seedlings came up and was even more surprised at how few survived. He cleared the ground in order that no effects could take place by existing plants or weeds crowding out others, and he meticulously observed number, variety, size etc of different weeds and wild flowers that grew there.
Darwin recorded this experiment under the heading ‘Weed Garden’ in his Experimental book. Selecting a small plot of land in the orchard protected from large animals, he cleared it of all perennials in January 1857. Here are extracts from his notebook and letters indicating its development.
Experimental Notebook – March 1857
Weed garden – Old shrubbery & then Strawberry neglected Bed. Piece of foul (but not very foul judging from rest) ground in Orchard, which had been (Shrubbery and then for a year or two) strawberry Bed— in size 36 inches by 24 inches.—(protected from large animals) Dug in January & cleared of all perennials— Early in March seeds began to spring up: marked each daily.
Letter from Charles Darwin to Joseph Hooker,21 March 1857
I am amusing myself with several little experiments; I have now got a little weed garden and am marking each seedling as it appears, to see at what time of life they suffer most
Experimental Notebook
March 31st About 55 marked, of which about 25 Killed already
April 10th Pulled up 59 wires marking where seedlings before development of two leaves had been devoured, I suppose by slugs, & many drawn out by worms, & apparently some beaten out by heavy rain. All, or nearly all earliest seedlings thus destroyed. I think certainly grass seedlings escape better than others. [No doubt they suffer more by being open & exposed to weather & only few, so better chance of being devoured]
Letter from Charles Darwin to Joseph Hooker, 12 April 1857
I have been interested in my "weed garden" of 32 feet square: I mark each seedling as it appears, and I am astonished at the number that come up. and still more at number killed by slugs etc. -- Already 59 have been so killed; I expected a good many, but I had fancied that this was a less potent check than it seems to be; and I attributed almost exclusively to mere choking the destruction of seedlings. -- Grass-seedlings seem to suffer much less than exogens. -
Experimental Notebook
April 20th Pulled up 28 wires, dead. – (I think dry weather is beginning to tell against some)
May 8th Pulled up 95 wires. – (I suspect that some seedlings are killed by drought.)
June 1st Pulled up 70 wires. – Left still 80 still living of several Kinds most Ranunculus & Grass Spergula – Labiatae Thistle (1 Nettle, some Crucifers (Extremely few have come up during all May)
Letter from Charles Darwin to Joseph Hooker, 3 June, 1857
My observations, though on so infinitely a small scale, on the struggle for existence, begin to make me see a little clearer how the fight goes on: out of 16 kinds of seed sown on my meadow, 15 have germinated, but now they are perishing at such a rate that I doubt whether more than one will flower. Here we have choking, which has taken place likewise on great scale with plant not seedlings in a bit of my lawn allowed to grow up. On other hand in a bit of ground 23 feet, I have daily marked each seedling weed as it has appeared during March, April and May, and 357 have come up, and of these 277 have already been killed chiefly by slugs.
Experimental Notebook
July 1st 13 of the 80 are now dead, leaving 67 alive a few more & but a few more seedlings have come up now there are 67/357 alive ie not 1/5 alive. Evidently the risk is in early state.
Letter from Charles Darwin to Joseph Hooker, 1 July 1857
Thanks for your interesting note about embryonic leaves: after I had sent it, I began to think about cotyledons, and marvelled that I could not remember having ever read any discussion on their resemblances and dissimilarities in allied plants. How curious that the subject shd never have been taken up! I do not even know whether functions of the cotyledons are same as leaves, or whether they serve, also, as receptacle of nutriment: I have noticed in my weed-garden that their destruction seems always to kill the plant.
Experimental Notebook
Aug 1 5 more of the 80 now dead – leaving 62 alive 62/372 62/310 – say between 1/5 & 1/6 have survived.
Evolution and the Weed Garden
April 10th Pulled up 59 wires marking where seedlings before development of two leaves had been devoured, I suppose by slugs, & many drawn out by worms, & apparently some beaten out by heavy rain. All, or nearly all earliest seedlings thus destroyed. I think certainly grass seedlings escape better than others. [No doubt they suffer more by being open & exposed to weather & only few, so better chance of being devoured]
Letter from Charles Darwin to Joseph Hooker, 12 April 1857
I have been interested in my "weed garden" of 32 feet square: I mark each seedling as it appears, and I am astonished at the number that come up. and still more at number killed by slugs etc. -- Already 59 have been so killed; I expected a good many, but I had fancied that this was a less potent check than it seems to be; and I attributed almost exclusively to mere choking the destruction of seedlings. -- Grass-seedlings seem to suffer much less than exogens. -
Experimental Notebook
April 20th Pulled up 28 wires, dead. – (I think dry weather is beginning to tell against some)
May 8th Pulled up 95 wires. – (I suspect that some seedlings are killed by drought.)
June 1st Pulled up 70 wires. – Left still 80 still living of several Kinds most Ranunculus & Grass Spergula – Labiatae Thistle (1 Nettle, some Crucifers (Extremely few have come up during all May)
Letter from Charles Darwin to Joseph Hooker, 3 June, 1857
My observations, though on so infinitely a small scale, on the struggle for existence, begin to make me see a little clearer how the fight goes on: out of 16 kinds of seed sown on my meadow, 15 have germinated, but now they are perishing at such a rate that I doubt whether more than one will flower. Here we have choking, which has taken place likewise on great scale with plant not seedlings in a bit of my lawn allowed to grow up. On other hand in a bit of ground 23 feet, I have daily marked each seedling weed as it has appeared during March, April and May, and 357 have come up, and of these 277 have already been killed chiefly by slugs.
Experimental Notebook
July 1st 13 of the 80 are now dead, leaving 67 alive a few more & but a few more seedlings have come up now there are 67/357 alive ie not 1/5 alive. Evidently the risk is in early state.
Letter from Charles Darwin to Joseph Hooker, 1 July 1857
Thanks for your interesting note about embryonic leaves: after I had sent it, I began to think about cotyledons, and marvelled that I could not remember having ever read any discussion on their resemblances and dissimilarities in allied plants. How curious that the subject shd never have been taken up! I do not even know whether functions of the cotyledons are same as leaves, or whether they serve, also, as receptacle of nutriment: I have noticed in my weed-garden that their destruction seems always to kill the plant.
Experimental Notebook
Aug 1 5 more of the 80 now dead – leaving 62 alive 62/372 62/310 – say between 1/5 & 1/6 have survived.
Evolution and the Weed Garden
He continued to monitor the plot, marking new plants, counting the ones that had perished, and suggesting possible causes of death, until 1 August 1857. Out of 357 plants he had marked, he found 62 had survived
The weed garden also is mentioned in his master work “On the Origin of Species”, published in 1859:
‘With plants there is a vast destruction of seeds, but, from some observations which I have made, I believe that it is the seedlings which suffer most from germinating in ground already thickly stocked with other plants. Seedlings, also, are destroyed in vast numbers by various enemies; for instance, on a piece of ground three feet long and two 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.
Repeating the experiment
Repeating the experiment
Rowan Blaik is the head gardener at Down House where Darwin lived and conducted his “weed garden” experiment. They repeated the experiment to see if Darwin got it right:
“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.”
What can we learn from Darwin’s Weed garden?
First of all, that Darwin was a great experimentalist, and he meticulously observed, counted, record, with such detail that his experiments, such as the weed garden can be recreated and observed by others, as has been done. Today there are even instructions which have been written for schools to do this to explore this experiment and see how Darwin used in as part of his theory of evolution.
Secondly, that the fact that nature kills off 83% of weeds over a fairly short period of time are in themselves a small scale demonstration of the pressures that plants are under, and how these pressures were an essential part of the ongoing process that eventually gave rise to the wide diversity of life on earth. That is why it is present in Origin of Species – it is just one more example to demonstrate evolutionary pressures.
Thirdly, while the fecundity of weeds is halted by climate and predation, unfortunately the same factors are at work against crops planted by human beings. Nature knows no privilege, and so we have to work hard to prevent our crops being damaged by evolutionary forces at work in the natural world.
Glossary
Cotyledon: an embryonic leaf in seed-bearing plants, one or more of which are the first leaves to appear from a germinating seed
Referenceshttp://www.bbc.co.uk/blogs/gardening/2011/08/the-weeds-are-having-a-tough-t.shtml
https://www.darwinproject.ac.uk/sites/default/files/learning_resources/Experiments%20Activity%203.pdf
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