Seedlings with different attributes could produce different sort of plants...
High strength could produce tall, strong trees...
High speed, small weeds and grass which grows quickly... (these produce seedlings from stalks..?)
High power would be perfect for small resilient shrubs that cling to the planets with a tenacity not seen from the others...
Then of course, you could work out a formula that decided what each aspect regulated...
And as the seedlings were produced, there stats would be slightly influenced by the planet they're on, but NOT as drastically as with the main game...
slight changes in attributes... and what you plant could alter the stats of the planet also...
As plants GROW on the planet, the Core Energy should drop, seeing how it's be used up to produce the plants... which in turn would effect the growth rate of plants. As plants or seedlings DIE on the planet, the remaining energy from entities could be absorbed by the planet... and the planet it'self could grow...
In which case, pruning would be useful... and since the plants ARE sentient, you COULD still have the combat aspect, but to a scaled down degree... optional perhaps... maybe the A.I is permanently set to 'DO NOT ATTACK TILL YOU ARE FIRST ATTACKED!'