How this was made

Every week or two, a volunteer at the Australian National Botanic Gardens in Canberra walks through the Gardens and writes a short leaflet describing the plants in bloom along that day's walk. From 1997 to 2016 the Gardens published it as In Flower This Week. Since August 2016 the Friends of the Gardens have carried it on as Flowers, Fruit & Foliage. Together the two series cover nearly thirty years.

This website uses those leaflets to answer a simple question: are the plants in the Gardens flowering earlier than they used to, and if so, why?

What was done, step by step

1. Every leaflet was collected

   899 leaflets from the Gardens (1997 to 2016) and 248 from the Friends (2016 to today) were gathered. Most are still online. About 180 had gone missing, including many of the Friends' older leaflets after their old website closed. Copies of those were found in the Internet Archive, a public library of old web pages.

2. The plants in each leaflet were picked out

   In every leaflet, the plants being featured are printed in bold. A computer program read each leaflet and wrote down every bold plant name, together with the leaflet's date. The Gardens' leaflets are web pages. The Friends' leaflets are printed sheets saved as PDFs, laid out in two columns with numbered stops, and a few store their text in a scrambled form that had to be decoded. This gave 22,000 records of a plant in flower on a particular day.

3. The plant names were tidied up

   Botanists sometimes rename plants, and a few names in the leaflets were misspelt. Each name was checked against the Atlas of Living Australia, the national list of Australian species. That way the same plant is counted as one plant across all the years, even if its name changed.

4. Each plant's flowering time was worked out for every year

   For every plant, the dates it appeared in the leaflets each year were noted, and the middle of those dates was taken as that year's flowering time. Only plants seen in at least eight different years were used, which left 436 plants. Then came the key question: did that flowering time move earlier or later as the years went by?

5. The results were compared with Canberra's weather

   Official temperature records for Canberra from the Bureau of Meteorology, and rainfall records, were used to see whether plants flowered earlier in warmer or wetter years. The Bureau's long-term record currently ends in 2024. For the months since then, a weather model that closely matches the Bureau's figures was used.

6. The work was double-checked

   In 2014 the leaflets changed format. They began coming out every two weeks instead of every week, and each became a fixed walk of 15 stops instead of about 20 plants. With fewer leaflets and fewer plants, a plant tends to be spotted a little later, even if nothing has changed. That's why the middle of each plant's flowering time is used rather than the first day it was seen. The analysis was also repeated in several other ways, for example treating the early years as if they too were fortnightly, and using the Gardens' leaflets on their own. The result held each time, and nothing changed when the Friends took over the leaflets in 2016. A separate page lets anyone compare a leaflet with what the computer picked out, to measure how accurate it was.

What was found

Things to keep in mind

• Every other assumption is listed on the Findings page and in the report.
• The leaflets were written to guide visitors, not as scientific records. A plant only appears when a volunteer chose to walk past it and mention it.
• Because of this, the result for any single plant is not reliable. The overall pattern across hundreds of plants is much more trustworthy.
• Since 2014 each leaflet features 15 plants and comes out every two weeks, so recent years have about a third as many records as the early years. The analysis allows for this, but it does make recent years less certain.
• There are no leaflets for April to June 2020 or for mid-August to October 2021, the periods of COVID-19 restrictions and lockdown in Canberra.
• The findings are best read as a strong hint, not as proof.

The rest of this website

With thanks to the volunteers of the Australian National Botanic Gardens and the Friends of the ANBG, who wrote every one of these leaflets.