Several things ...

1 - It prefers afternoon shade in Az. It's cooking.

2 - You are watering too often and too little. The frequent short waterings keep the top few inches of the soil moist, so that's where the roots stay, and the heat kills them. Water it once or twice a week, until the dirt (as tested by a moisture meter) is wet 8-10 inches deep.

OR, if you are in one of the clay-dirt areas of the valley, it's overwatered.

Either way, check with a moisture meter and adjust your watering.

3 - Doesn't need that much fertilizer.

Short lived, self seeding annual...if it has flowered then it is normal for it to die I expect.

You don't say where you live in AZ, but in the lower areas may have more than one crop annually...maybe others with experience can say.

Actually I've found a couple of sources on the web (where all reliable information comes from - lol) that suggest that catnip is a "short lived herbaceous perennial", so I guess it won't live forever but it has the capability to live for more than two years. I am going to try watering it every two days and see if that makes a difference (based on lazygardens' suggestion that it may be overwatered.)

If I let catnip get more than 2-3 hours of sunlight in a row, it always dies like this in the summer for me. All my catnip plants died this year because I tried to give them a little too much sun.

I raise my catnip like I do the mints, more shade, no direct az sun, it fries it..I water it slow and deep about two times a week, and no fertilizer, as the cats eat it and am afraid to have them ingest any of that..twice a year I do side dress with some bone/blood meal.about four times a year,.but it can't take the summer sun at all down here in the low desert..it seems to reseed itself pretty well.

@iAndy, @quotetheraven - thanks for the additional input. It does seem like it's just getting fried by the sun - I'll hit Home Depot this weekend and see if I can pick up some kind of a sunscreen for it. I would hate to lose it all like I did last year (and my cats would hate it even more!)

Thanks...

The temperature zoomed to 112 yesterday and really hammered what was left of the catnip. To give it a fighting chance I put up an emergency sun shield. The rest of the patch is between two houses and only gets 2-3 hours of sun a day - I'm hoping that at least some of the plants will survive the rest of the summer.

I live in the high desert valley of northern Utah, and catnip doesn't work for me either. The tag always says full sun for some reason, but it simply can't take the southern sun out here. Completely dead in a week or so, even if I water it well. I might try again this year in part sun, for my kitty 's sake, but I'm nervous about it because I've already killed two plants.

I have catnip growing in my yard like weeds now. I actually pick some out of the ground to keep it manageable because it gets really big (each plant can get 4-5 feet in diameter). What's cool is it even grows in the full sun areas now once it started reseeding itself. It especially likes the mulched areas.

My cats love it, although I got freaked out last year when one of my cats started drooling a lot after rolling around in the dried up section so I removed most of the dried up stuff.