Every year there are plans to do this: 2015 this is the year. The Japanese knot-weed growth is going to be recorded. How fast does it grow in a day, 2 days a week? Seems like it grows so fast you can see it. You can actually hear it as it pushes up from under the leaves. Yeah, its that fast.
The plan is to record the growth and the rainfall for each day.
Shoot height on plant #1: 8mm, height on plant #2: 2mm and 11mm.