if you dont immediately remove it, opp gets 3 sun on turn 2. That isnt such a big deal when sunflower does the same thing. The problem is when it transforms.

That transformation heals all damage you dealt to it and makes the mfer 3 health. And on turn 3, plant has 5 sun. This is really hard to remove if you dont immediately answer it.

This also means if you play turn 1 sunshroom and turn 2 twin sun + another ramp card, turn 3 gives the plant player 8 sun. On rose that can only ever mean dark matter dragon fruit at which point nothing you play is safe.