Nettle Vine is a plant exclusive to the Hamlet DLC. It can be harvested without the need of a tool, and will provide one Nettle. Nettle Vine has four states, but only one of these could make it grow.
Nettle Vines will only bloom when they are both Wet and fully grown. They spawn into the world fully grown, and can be harvested during the Heavy Fog and Rain of the Humid Season. However, once a Nettle Vine has been harvested or replanted, it will require three days of continuous wetness (or Wickerbottom's Applied Horticulture) to fully grow again. Once a vine has fully grown, it can be harvested at any time while wet. The practical way to regrow harvested Nettle Vines is with the use of a Sprinkler. Nettle Vines will also only bloom on Deep Rainforest turf (in which they spawn) and on Dense Turf. If they are planted on any other turf, they will wither and never bloom, even if it gets wetness.
The sparse placement of Nettle Vines combined with weather-bound harvest availability poses a significant time-sink for players who choose to gather Nettles early on. However, the Fountain of Youth island is guaranteed to contain 2 large clusters of Nettle Vines within the deep rainforest where the player first emerges from the ruins. It may be wise to utilise the Gas Mask for the first lush season, in order to have additional time to collect nettle plants.
Nettle Vines used to require 1.5 days to regrow, and they had a bug which their growth timers would reset to zero if they dry out before they fully grows. Both these were changed and fixed in the February 27, 2019 update.