Answer: This plant needs a well drained soil to grow well. Based on your description I do not think watering it alone would have caused the shriveling, unless it is in a very poorly drained location adn then the watering combined with the downpour may have done it. If the soil became sopping wet and fully saturated and the roots were left in very wet soil for several days, this could cause it to happen due to root damage showing up as foliage symptoms. There are also some other possibilities such as it had failed to root out into the native soil and the heat stress caused it to succomb as a result, or there are spider mites. Since it is a new plant, I would suggest you consult with your retailer and/or county extension to see if they can help you trouble shoot. Good luck with your cotoneaster.
Q&A Library Searching Tips