Water thoroughly when the potting soil feels only slightly damp to the touch. You do NOT want a plant, even rosemary, to dry out in severe heat. Remember, I said to water thoroughly.

A very simple 'fix' for an ordinary commercial potting mix would be to add lots of perlite....about three parts potting mix to one part perlite. Buy the coarser perlite and rinse it well before using.

Rosemary is also very prone to spider mite infestations, something that often gets much worse in the heat of the summer. A bad problem would certainly cause the foliage to be browned and dried looking....dead.

I have a brand new Rosemary Organic Herb plant I got from the grocery store. When I got it, it looked like the healthiest one there, even a couple unknown sprouts in the corner that appear to be rosemary babies. I picked off maybe 5 dried leaves when I got home & placed it in the window sill. I haven't been watering it.

In a period of about 6 days the entire plant seems to have dried up and died, the needles brown & crunchy even though the soil is slightly damp 1" down. I was not sure what water schedule the store had, so I thought it may have been overwatered & the soil was very damp & clumped together 100% pure potting soil. Transplanted into 30% sand, 30% perlite, 30% potting soil to provide better drainaige & save it. I gave a 1/2 cup of water & let it sit outside for a day. I clipped off the dried out stems. Today there is at least another 1" of dead plant.

What should I do? : (

You need to water from the bottom. Like set it in a bowl of water deeper than it is, and let the top get wet. Remove from the bowl and don't water again until the top is really dry.

I do this with herbs I grow in the house, but most I stick in the ground outside. Rosemary is one of the easiest. I live in a really hot dry climate, and my whole yard is covered with it. It's a friendly weed.

Okay that may do a world of good, for future watering.

Also, I noticed when changing the soil that the roots were sort of brown & limpy, maybe even hollowish Iinside. Are there any steps I should take right now, to help the roots? Does it need to be dumped out to dry the soil, trim roots or the plant? Does the soil composition seem good for this situation?

This is a pic of what rosemary roots should look like, white & feathery almost. Mine did not look this way, and were brownish & stringy like an old rotten chive.

As well as letting it dry out I would put it outside. There is very likely insufficient light for Rosemary indoors.

Thank you @desertdance. After a couple days I will try this! Ive never heard of this before, and sounds like a great tip! So a deep saucer or a bucket & set the rosemary into it for a few moments & let it absorb through the bottom. Then I remove it right? Dont let it sit in any type of saucer until the soil dries again?

@ floral_uk I placed it in a shady location of the porch, with fresh dry dirt.

As the rosemary was withering & getting crunchy (Im used to leaves being yellow from overwater), so I started watering it more. I replaced all the wet soil & used the same exact dirt as before, and put dry dirt into the pot with pebbles at the bottom last night. It has been in the dry soil for about 24hrs, if it has root rot, how long is appropriate to let it dry out?

Heres current photo:

Is all hope lost? : /