If you have cold winters and must bring rosemary inside each fall, you may find it convenient to grow it in a container all year round. Then you can move it wherever you want.
Set a small starter plant directly into an oversized pot that is 12 inches in diameter or larger and has drainage holes. Fill it with light, sterile soilless potting mix to prevent root rot. Clay, or terra cotta, pots are ideal for rosemary because their porous surface permits air exchange from within the pot. This reduces the risk of overwatering the plants. If a potted rosemary dries out too quickly in the summer sun, sink the pot into soil in the yard up to its rim. Water with dilute general purpose liquid fertilizer or add a slow-acting granular fertilizer to the planting mix beforehand.
Alternatively, transplant garden grown rosemary to a container each fall to bring indoors for the winter. Dig the plants and trim damaged or matted roots. Prune about one third of the top growth as well. Pot as described above. Leave the plants outside for a couple of weeks to let the plants adjust to their new container. Then bring them inside and set them in a sunny room.
Rosemary is particularly vulnerable to fungal disease from poor ventilation, so be sure it enjoys good air circulation at its indoor site. ‘Logee Blue’ is more resistant than most. Water it sparingly. In the spring, when the plants start growing again, add some dilute liquid fertilizer to the water, plant them out after the last frost.
