Copyright (c) 1988 Ludovic Robillard

The game starts at following hexagonal board:

Each player has 50 'grains' and 3 'seeds'.

PLANT - One or more connected grains of the same color with contact to at least one seed. 
A plant with no seeds is a dead plant and is removed from the board.
A plant may perform the following actions: 
Grow - drop a friendly piece (i.e., seed or grain) at an adjacent empty cell.
Move - move one of his pieces to an adjacent empty cell.
Trim - remove one grain back to the reserve.
Recoil - remove one seed back to the reserve. A plant can only recoil if it has at least two seeds.
Plants can capture enemy plants. Captures are custodian (one or more enemy pieces in a straight line are captured when placed between two friendly pieces).
After the capture, any resulting dead plant is removed.
All captured grains are returned to the owner. 
The seeds are removed from play and cannot be reused.
Suicide rule - A piece cannot be placed in a cell where it would be captured, except if itself captures enough stones so to remove that threat (check the last two examples).
Ko rule - The player cannot repeat the position from the previous turn.
EDGES - The board is (almost) cylindrical around the blue line (cell B is adjacent to cell b).
The red line cannot be crossed and may be used (it acts as a friendly piece) for custodian captures.
There is an extra capture rule regarding columns: if a column does not have at least two vertically adjacent empty cells, all pieces (of either color) on that column are captured (and eventually all resulting dead plants). 
SETUP - Each player drops one friendly seed into an empty cell. 
The second seed must be at a distance of at least three cells from the first.
In the first three turns, all pieces must have a minimum distance of three cells to any enemy piece.
MOVE - On each turn, a player may drop one or more seeds into empty cells and must manipulate each one of his plants.
The number of action per plant equals the number of seeds that plant has at the beginning of the turn
These number of actions must always be performed in full (the player cannot skip actions).
The player cannot use the actions of a plant to manipulate another plant.
GOAL - Wins the player that captures all enemy seeds.

Plant actions imply some possible effects: (a) fusion - by growing, a plant may fuse with another friendly plant; (b) massive trimming - by removing a grain, a part of the plant may be without contact to a seed, and so it is removed from the board; (c) separation - a plant with more than one seed may separate in two.

A simple capture

[In these diagrams, black seeds have blue grains and white seeds have yellow grains]

After the grow of the blue plant (by dropping the marked blue grain), the marked yellow grain was captured.

A capture with an extra dead plant

In this case, after the grow of the marked blue grain, two yellow grains were captured (the marked ones).

After this capturing, a new dead plant was created (the two isolated yellow grains), which is also removed from board.

Suicide are illegal

The grow showed by the marked yellow grain is illegal, since that grain could be captured without any extra action.

Not a suicide

Growing the marked yellow stone is no longer illegal, since by moving there it captures the marked blue grain.

This game has some extra rules (dealing with plant parasites and fast grow) which I believe are optional and do not add much more interest to the game. There is a detailed document with the complete rules (in French).