Fastest growing plant
Who
Bamboo plant
What
0.00003 kilometre(s) per hour
Where
Bamboo plant
When
The world record for the fastest growing plant belongs to certain species of the 45 genera of bamboo, which have been found to grow at up to 91 cm (35 in) per day or at a rate of 0.00003 km/h (0.00002 mph).

According to the RHS Dictionary of Gardening, there are approximately 1,000 species of bamboos.  The tallest recorded in the tropics was reportedly 40 m (130 ft), in Europe and the USA 20-30 m (65-98 ft) has been the tallest.