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| 12 January 2018 |
This is a question I am asking myself for quite a while now as it feels like I am seeing the first crocus flowers earlier and earlier each year. To answer this question I went back to the photos I have taken each year of my allotment. As the first flowers are always eagerly anticipated I normally take photos of the first crocuses and snowdrops I can see each year so I have a pretty good photo record of these flowers from 2012 until now.
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| First crocus flowers seen on my allotment |
As you can see in the graph above, in 2012, 2013 and 2015 I recorded the first crocus flowers in mid February. In 2014 the first crocus flowers were out at the beginning of February. In 2016 and 2017 the flowers opened towards the end of January and this year I have seen the first crocus flowers on the 12th of January!
Having the dates of first flowering for seven consecutive years, I was
actually able to test the above question statistically, with a so-called
Spearman rank correlation test. Using the one-sided version of this
test, which specifically asked the question 'Has flowering begun
increasingly earlier throughout the period 2012-2018?', I could confirm
this with a probability of 99.91%, corresponding to a P-value of
0.0009 in the statistical test, which is considered a highly significant
result in statistical terms. To answer the question in the title, yes, crocuses tend to flower
earlier every year on my allotment, even though 2015 appeared to
represent a bit of a blip.
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| 16 February 2013 |
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| 2 February 2014 |
I am not the only one recording earlier flowering dates for plants. A
study derived a 250-year index of first flowering dates for 405 plant species in the UK and found that British plants are flowering earlier now than at any time in the last 250 years. As there is a strong correlation between temperature and the date when flowers first open each year we can assume that our climate is getting warmer.
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| 24 January 2016 |
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| 22 January 2017 |
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