The tooltips for Spriggan form’s Summon Vines skill are inconsistent between the tooltip on the skill when you are in Spriggan form:
https://imgur.com/fiG9F4z
And the tooltip on the Vine nodes (all of them give the same tooltip) on the skill tree:
https://imgur.com/Lb4nERW
The Skill bar tooltip appears to be correct, since it says that it summons 3 Vines (which it does) & has the poison chance underneath Attunement scaling.
Edit: From @Cujo