Awesome

hedera

paint 3D ivy in Unity, simulate growth
includes textures, shaders, and 5 presets for painting realistic ivy, cartoon ivy, or even ropes and cables
curious about vert count / polycount? download sample ivy .OBJ (right-click Save As)
- merge multiple ivy meshes to save draw calls, or just let static batching work
- randomize vertex colors for subtle color variation, auto-unwrap ivy UV2s for lightmapping
- store ivy meshes directly in your project, or export to .OBJ (note: OBJ file format doesn't support vertex color nor UV2)
25+ different ivy settings to tweak for your own presets! guide and user documentation is on the Wiki
tested on Unity 5.6.7f1 and 2019.1.8 and 2021.2.0f1 (but probably works ok on other Unity versions too)
no HDRP or URP shaders included so you have to swap in your own, but everything else will still probably work OK
changelog

(recommended) in Unity's Package Manager, add https://github.com/radiatoryang/hedera.git as a Git URL package full instructions
or manually download the latest .ZIP from Releases and unzip to /<your project folder>/Packages/com.radiatoryang.hedera/
or clone this Git repository as a submodule into /<your project folder>/Packages/com.radiatoryang.hedera/

GPL2 (due to original author's use of GPL2)

You can use the ivy assets / generated meshes and results, with any or no license, in commercial or closed source projects. GPL2 focuses on the code, and does not apply to program output.
All code is editor-only and stripped upon build, which (I think) avoids GPL2's wrath. This code basically won't be in your build, which means you aren't distributing it.
If you use this code / tool in your own tool AND distribute that tool, then your tool must use GPL2. Note that Unity Asset Store bans licenses like GPL, so no part of this tool can ever be put on the Asset Store.
(but I am not a lawyer, this is not legal advice, etc.)

donate to the original Ivy Generator author (Thomas Luft): http://www.loim.de/ivy_generator_donation/
to donate to me, just go to my itch.io page and buy / tip whatever you want: https://radiatoryang.itch.io/