From the CO2Science.org archive: Hypericum perforatum is a popular herbal remedy despite an off-putting name that sounds like St. John should reach for the salicylic acid, and it actually may have some efficacious properties, namely for the alleviation of mild depression. What’s more it’s apparently easy to grow in gardens, so easy that you must take care not to let it spread too much and become a pest. And take care not to eat it because it is toxic, and “notorious” for interacting with other medicines. But it interacts happily with the extra CO2 you emit. From 2004 to 2019 there were 12 studies showing that an extra 300 ppm CO2 in the air boosted its growth by 39.7%.