If damage would be dealt to Phytohydra, put that many +1/+1 counters on it instead.
If Phytohydra blocks or is blocked by a creature with first strike or double strike, Phytohydra will get the counters during the first-strike combat damage step before it deals its own combat damage during the second combat damage step.
If another effect would prevent damage from being dealt to Phytohydra or replace it with something else, Phytohydra’s controller chooses which effect to apply first.