[ukmicky (OP)]

Plants require C02 and we are constantly being told that the atmosphere contains more C02 than ever before.

So why hasnt their been an explosion of plant life . Or at least a measurable increase in the health of your average plant.

Why do my house plants still die ,shouldnt it have become easier to grow healthy plants. 

[Atomic-S]

What percentage increase has occurred in the atmosphere?

[Henry Pool]

Carbon dioxide went up from 280 ppm's in 1960 to 350 ppm's now (0.035%).

[Madidus_Scientia]

Which is an increase of 25%, quite significant

According to this website http://www.applet-magic.com/CO2plants.htm most plants increase growth by 41% when CO2 is increased by 100%. So since the increase since 1960 is 25%, I guess we might expect a 10.25% increase in plant growth, assuming it all scaled down reasonably linear, and assuming that all plants in reality were not bottlenecked by other factors such as sunlight/water/nutrients. So i'm not sure if a significant increase in plant growth has been measured or not but if it has I wouldn't call it an explosion, and chances are your plants are dieing from lack of sunlight, water or nutrients, regardless of CO2 levels.

[Henry Pool]

I think if your plants still die you don't talk enough to them and they don't get water at the right time or in the right way?

[frethack]

Not to mention that in your house the CO2 concentration is WAY above atmospheric levels. 

[Jessica H]

I've seen pictures of tomatoes grown in high CO2 conditions and they were way bigger in comparison to the controls.  That's an interesting related question though, to wonder if crop yields would eventually increase!  I think you would also be able to grow more food in some of the cooler climates because warming up the climate would extend the growing season. 
 
Hmmm...maybe blowing CO2 as you talk is the reason that talking to your plants works...