Which time is best for foraging nettles?

Gillian Edom, the author of ‘From Sting to Spin’, kindly shared a table from her Mphil thesis on nettle fibre extraction about harvesting / foraging dates. Seems although there is not much difference in the yield, the fibres are easier to extract early in the season.
As with all foraging, only collect what you can process and consider the wildlife that feeds on nettles!