Salix darts through the portal after Shooting Star, moving off to the right side after he exits, but he remains fairly close to the main group--five feet from the nearest other member. If there happens to be a conveniently-grouped bunch of guards -- or at least multiple guards within a 30' diameter -- he lets fly with a spore from his chest that bursts into a Fatiguing cloud, enveloping as many guards as he can (and excluding any team members, if he has to). If there is only a sole remaining guard, or multiple guards too far apart to be affected by the Fatigue, he fires off a Stunning dart at a single guard instead.
If all guards on the roof have been taken down, he simply tears a particularly large flower off of his own body, tosses it to the ground, and begins to channel mental energy into it. The flower blooms and a tangle of vines and leaves sprouts from its base, growing rapidly into a vaguely humanoid shape almost as tall as Salix himself, with the flower in place of a head.
(OOC: Fatigue 6, ranged, area (cloud - 30' diameter), selective; or Stun 10, ranged, attack +11, power attacking for –3/+3, taking 10 on the attack if minions; or Summon Minion.
EDIT: Thanks, Elric; took your suggestions.)