Cant wait for an update or a sequel...
The framework for this game is awesome, it certainly has potential.
The problems however are balancing.
Shielder trees are fine
Attacker trees are fine. If anything their seed damage should be dropped and collision damage raised to further increase the dependence on shielders.
Archer trees definitely feel underpowered, especially compared to attacker trees in terms of mana usage and damage output.
Mana Shrubs are fine, If anything their power output could be dropped then upgraded into the current level.
I can say I have never built a leaflet shrub. Max power and max health of trees have never been an issue. If Flower turrets were viable then I can see them being useful and actually being used.
Flower turrets as many have said are awful. Well not awful, just inferior to the other trees. They are the joint last tree to get out, their damage output is atrocious even at max upgrade. Either increase their damage or drop their production cost and make them possible to build straight away.
Pollen turrets I think i used once and I died, so i can't really comment.
Finally the last two problems I had with the game were as follows:
1) You got more points for taking longer to win???
2) If you "destroy" (reduce the hp to zero) the enemy base before nuke stage it moves onto the next stage instead of dying(and restores hp). This would be fine if you got more points for getting to nuke stage faster =S
The ways I've won with that I can think of:
1 mana, 5 shielders, 4 attackers
2 mana, 1 shielder, 7 attackers (can "destroy" enemy base 2 stage before nukes)
2 mana, 2 archers, 6 flower turrets
(to see if it was possible, and it took ages. I also destroyed my shielder and attacker)