Garen vs Katarina Mid Matchup
Garen Mid wins 55.6% of 671 Low Elo games against Katarina Mid, +1.5 points vs expected, 2-patch window 26.19-26.20.
Researched on LoL patch 26.20. Tips are written to hold at any rank; stats come from Low Elo ranked games up to patch 26.20.
How to play as Garen
Hold Decisive Strike(Q) for Katarina's Death Lotus(R) if she channels within your reach; Katarina players explicitly warn that your silence can end her ultimate.
Decisive Strike(Q) silences Katarina and can interrupt Death Lotus(R) if she channels within reach; Katarina players call out this interaction as a major danger in the lane.
Perseverance(P) restores Garen's health when he has avoided recent damage, so Katarina's occasional poke may not keep his health down if she stops pressuring him.
How to play as Katarina
Do not channel Death Lotus(R) while Garen can reach you with Decisive Strike(Q); his silence cancels the channel, so wait for Q to be spent or for him to be out of range.
Use Bouncing Blade(Q) to break Perseverance(P) when Garen backs away to recover, but avoid trading into his Q and E after level 6; Katarina players warn that his sustain and all-in make extended lane pressure difficult.
Sources
These notes come from r/KatarinaMains, checked against the champions' abilities.