From the CO2Science archive: The approach of autumn in Canada means fresh apples will soon appear at our farmers’ markets. How will they fare with all the extra CO2 in the atmosphere? Here we only have two studies to go on, both from 1988 and both referring to the behaviour of one-year-old seedlings. In response to an extra 300 parts per million (ppm) the little apple trees experienced, on average, 105.5% more photosynthesis (standard error 18.7%). After an extra 600 ppm the plants experienced 224.5% more photosynthesis (s.e. 39.2%) and after an extra 900 ppm they experienced an extra 366% growth (s.e. 79.2%). So if an apple a day is the key to health, extra CO2 seems the key to health for the apple.