Blue Rug juniper turning brown
Junipers (7) planted last September. Morning direct sun. They were great til it got warm. Well draining soil with sand. 2 inches of bark chips. Water 2 minutes twice weekly until it started 90 degrees, then to 4 minutes twice weekly. The ones turning most brown get the most sun. The nursery says too much water which seems inconsistent with fact that ones getting worst get the most sun
This looks consistent with watering problems. It could be too much or too little, or it could be something is wrong with the root system, which could be water related or due to something else such as a tight root ball. 2 minutes and 4 minutes of watering doesn't really tell us anything about how much water the plants are actually getting. In fact, it doesn't sound like much at all. However, the best way to know what the soil moisture situation is like, is to carefully dig up one of the plants and inspect the roots and the soil in the hole. The soil should be moist down to the bottom of the hole, but not saturated. If it is real soggy and the roots are brown and slimy then it is too wet. Of course, the opposite would be true if it is too dry; the roots would be brown and dry. An irrigation audit might be helpful too. This entails running the system for a period of time, measuring how much water was distributed, and then digging a hole after it has time to soak in and see how deep it actually penetrated.
Based on 90 degree weather, how much sprinkler time should I run ?
Time to run a sprinkler is not so much based on temperature as it is the output of the irrigation system, the infiltration rate, and the soil type. Here is a link to a fact sheet that I think may be helpful for you in determining the length of time you will need to irrigate - http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-7896/HLA-6610web.pdf.