I am assuming the drought is well known in your area, is that correct?
Do you normally have adequate rainfall or do you have a water system set up for your plants?
Here is one way to look at it: If everyone in your area is experiencing the same situation, then the buyers may be aware, and would certainly understand if normally there is no need to extra irrigation, so you do not have a system set up to do it.
It is not as though once you opened escrow you decided to stop watering the plants to save money, right?
So, in concert with the other advice you've received so far, discuss the situation with your Realtor, who, I would think, have some suggestions. Preventing surprises for buyers is ALWAYS a good idea.
Best of luck to you.
I would concur with the previous commnets. Best thing would be to address this with the Buyer via their agent to make sure there is no misunderstanding whan it closes. In California, we all understand water conservation. Good luck to you.
Paul is absolutely right. If the problem occurred after inspection, I recommend you contact the buyers agent and apprise them of the situation as soon as possible. Also do this even if the condition was present at inspection, because it MAY have been overlooked by the inspector and/or the buyer if he/she was not present for said inspection. At worst, you may be required to replace the dead/dying shrubs or provide a credit to the buyer for such. Better to solve this now. If you wait and find out later that it is an issue, your closing may be delayed. Best of luck!
Although I do understand the Draught situation as I am in the northern part of Marin in California. The water district has imposed a draught policy, although not as extended as it was when there was a severe drought, but I am seeing browing lawns, both in my own backyard and my neighbor's frontyard and other places.
If this happened after the inspection period, and you don't want your buyers to walk away, you might want to explain the situation to the buyers as this is not what you nor they can do, but perhaps negotiate some credit back so they can plant drought resisitent plants, which will be better in the long run anyway.