I moved a healthy rosemary plant indoors and it is now turning white and loosing leaves. It is in its original pot and soil, and was healthy when I brought it inside in October- before any frost. Sits in an east facing window. Is this a watering issue? I water usually once a week.
Rosemary (Rosmarinus officinalis) is a perennial plant but is usually wintered indoors in our climate.
Rosemary will not survive our cold winters outdoors but can be grown indoors. Pot it up using an growing medium for containers. Bring it indoors gradually so that it has time to acclimatize to its new environment – for an hour the first day, then back out to a cool spot. Increase the time indoors for a week or ten days. This is similar to the way in which we harden off our seedlings in the spring except that the plant is being moved from outdoors to indoor.
Your rosemary leaves are likely covered in powdery mildew, a common disease that occurs when plants are brought indoors. It is a white, powdery fungal infection that develops when air circulation is poor, encouraging high humidity. Shady conditions are also conducive to powdery mildew. This will not kill your rosemary but it weakens the plant. Control it by keeping the humidity at low levels. Allow the soil to dry out between waterings. Expose your herbs to plenty of sunlight, preferably a south facing window. If necessary, create a breeze around the herbs using a fan. Try spraying water on the leaves every few days to knock off the little white spores. As a last resort you can dust your herb with sulfur to bring mildew under control.
The following web site provides additional interesting information: https://www.doityourself.com/stry/identifying-diseases-that-harm-rosemary-plants#ixzz3KCiIEep0
You also might be interested in reading an article in the Star written by Sonia Day about overwintering rosemary. Here is the link: