From the CO2Science.org archive: Gymnocladus dioicus or Kentucky Coffee is a hardy, attractive deciduous tree that was the state tree of Kentucky until 1994 when they ditched it in favour of the Tulip Poplar. We don’t know why, as people genuinely seem to like the Kentucky coffee tree although many websites point out that the seeds are toxic when raw. As for “coffee” in keeping with the general trend to eccentricity in plant names, they can apparently be roasted and used to make a non-caffeinated coffee substitute, aka a drink that does not resemble coffee including in its effects. If however you just want to admire it for its attractive foliage, you’re in luck because a 2018 experiment showed an additional 300 ppm CO2 over 6 months increased its biomass by 15%.
15% is unusually small growth increase for +300 PPM CO2
only one study does not make a satisfactory article
you should look for multiple studies with the average of 30%+ growth for +300 PPM . CO2science was my favorite climate website while it was active, and i still like the archives, and the articles here This is the first time i've ever complained about one here.
From 1997 to about 2021 I read about 200 plant growth CO2 enrichment scientific papers. Based on the studies i read concerning food crops, i would say +300 PPM increased growth by about 30% on average.
The studies are tedious reading, and you have to pay to read some of them.
Thank you for covering 1998 to 2021 from the CO2science website