Answer: Wilting can be a sign of over or underwatering.
This plant is particularly sensitive to excess moisture and must be planted in a well drained location so that it is never sitting in water or saturated soil. In heavy clay based soil it may need to be planted on a slight slope to provide the drainage it needs.
On the other hand, in a drought situation long term water stress can cause wilting, too. This is especially possible with a new plant since it has a relatively small root system and potting mix tends to drain very fast. Junipers are deep rooted plants, so they can withstand dry conditions once they are established, but not right away.
Watering is done to supplement natural rainfall and help create a more ideal environment for deep new root growth. Your goal is to keep the soil slightly moist but not sopping wet. You should check down in the soil with your finger to see if and when you need to water. Check both the potting mix and the surrounding soil as they may dry out at different rates.
When you water, water slowly and deeply for a deep soaking then wait until the soil dries out a bit (check it and see) before you water again. After watering, wait a few hours or overnight and then dig down and see how effective your watering was, it can be surprising. Using several inches of organic mulch over the root zone can also help keep the soil moister longer as well as keep down weeds.
In hot, dry, or very windy weather you may need to water more often than you will in cooler weather, or in rainy weather. There is no magic timeframe I can give you, you just have to check and see. Eventually you will begin to know by experience when you need to water and how much.
Junipers are also sensitive to being planted too deeply as can happen if the soil settles more than anticipated after planting. It should be no deeper than it was originally in the container. If this has happened, dig it up carefully and reset it slightly higher.
Good luck with your juniper.
Q&A Library Searching Tips