First controller advice - Plant/Rad

Take Roots, the AoE immobilize, it does significantly more damage than other AoE immobilizes and synergizes well with Seeds of Confusion. Let the Confused mobs clump up, then immobilize them so they stay there.

The sleep Spore Burst is skippable.

Spirit Tree is fairly skippable, especially on a /Rad since you have a self heal.

Spores of Confusion: Take and slot up immediately, it's your signature power.

Vines: Long recharge, short hold duration, low accuracy. Useful for emergencies and Boss holding if you are willing to heavily slot it.

Carrion Creepers: An effective and extremely cool power, take it. Does damage, helps with confuse resistant enemies and takes the occasional alpha for you.

Fly Trap: An OK pet.

For Radiation Emission, you definitely want the three big debuffs; Radiation Infection, Enervating Field, and Lingering Radiation.

Accelerate Metabolism is an excellent buff.

Mutation and Fallout are optional; they are OK at what they do but if you aren't in a team they are useless, and if your teammates don't die they are also useless.

Choking Cloud: Not very useful on a Plant/Rad I'd think, although Fire/Rad and Elec/Rad do well with it I understand.

EM Pulse: A nice and very large Aoe Hold, I always take it.

I will second this. I don't even end up using CC on some of my rads, but on my Fire/Rad I never turn it off.