Asparagus growth speed is different during the day and at night.

During the day the average growth speed is 0.37 cm/hr.

At night it is 0.18 cm/hr.

So basically, the growth speed is doubled during the day compared with that at night.

The summary:

The sources:

1). 13.8 cm

2).  12.0 cm

3). 17 cm

4). 15.5 cm

5).  20.1 cm

6).  17.3 cm