When will it flower? Plants and Climate change
by Alistair Fitter
Alistair’s talk took place on Zoom on Saturday 10th July with thirteen members attending.
He began his talk by explaining that in the past the flowering of plants was like having a calendar. Snowdrops would flower in January, Primroses indicated the start of Spring, bluebells flower in April and there would be a sequence of flowering times. This is embedded in literature and Alistair quoted from Shakespeare, ‘A Winter’s Tale Act 4, Scene 4 and a Midsummers Night’s Dream Act 2, Scene 1.
However, that calendar is changing, and Alistair gave the example of the fritillaries he has in his garden. If you look in Floras in 1870, in Hooker: Student flora, fritillaries flowered in May/June, by 1952 it was April /May and in Alistair’s garden in York in 2020 they flowered in March/April. That is a big change.
According to the central England Temperature Record if the years 1960 – 1980 are classed as average temperature, then the years before were cooler than average but since they have been warmer with only one year being cooler. (naturescalendar.woodlandtrust.org.uk) Plants now flower earlier. In the period 2001 – 2016, fifteen years, Hazel flowered 31 days earlier, Lesser celandine, 27 days earlier and the Bluebell, 21 days earlier.
Richard Fitter (1913 – 2005), Alistair’s father an active conservationist and naturalist, was also a maker of records, and kept records of the first flowering dates of over 600 species of plants from the mid 1950’s to 2000. When the data was analysed, most plants flowered earlier, although there were a few exceptions. Six days earlier was common; however, some plants were six to eight weeks earlier.
Some plant’s first flowering date advanced 3.5 days per year.
By looking at the Flora’s, it can be seen that all native species were in flower by mid-June in the 20th century. Richard Fitter’s data from his own garden in Oxford records this as 10 days earlier and Alistair records, in his York garden, that this is a month earlier, despite York being 200 miles north of Oxford. This applies to both garden and native plants.
Alistair explained that there were several factors that influenced the flowering times. Firstly development and when the buds develop, secondly the day length and thirdly the temperature which can speed development and trigger flowering. He gave us the example of when the Wakefield and North of England Tulip Society held their annual show. The date was determined by when the Tulips should be at their best and this in turn was determined by the temperature in March. For every degree warmer the show was brought forward by three days. In 1827 the show was held late May to June and by 2020 the show was held in early May.
The change in flowering time can have knock on effects for insects and birds which rely on certain flowers being present when they emerge or hatch. Pollinators that are specific to certain flowers such as the Fly Orchid and particular pollinating wasp and the Orange Tip butterfly which relies on the seeds of the Cuckoo Flower. Hybrids can be more or less likely depending on the flowering times between plants such as the red and white Campion.
Alistair summed up his talk by saying that there had always been warm winters and cool summers, but this was becoming more frequent and that flowering times were shown to be a good indicator of climate change.
After a short break there were a few questions and observations with Sue Baddeley asking if there was a particular book or literature on the subject suitable for a novice. Alistair said that the literature was complicated and there might be an opportunity for someone to write a book on the subject. It was noted that some species of plant were moving north/higher, for example alpines, but at some stage they will not be able to escape the warmer weather and probably become extinct. ‘Creeping normal’ was mentioned with the example of insects on the windscreen, a feature on cars on the 1970’s but not so much in the 2020’s. Anne Bebbington mentioned the lack of teaching on the subject in schools and that in universities it is now Plant Science and Biochemistry and not Botany that is studied. There are, however, some proposals for a GCSE in Rural studies that is being developed by the exam boards.
Thank you to Alistair for an excellent talk on an interesting and topical subject.
July 22nd, 2021