Rosemary (Salvia rosmarinus) is a perennial herb in USDA zones 7 to 10, where it can be left in the ground year-round. But in colder regions you can also over-winter a rosemary plant by digging it up in the fall, planting it in a container, and bringing it indoors. But grown as an indoor plant, rosemary has some special requirements.
Rosemary is native to the Mediterranean region, and it prefers rather dry soil since it normally absorbs most of its moisture from surrounding air, not from the ground. Unlike most other plants, it prefers a dry potting soil when grown indoors. With the right technique and growing location, you can easily transplant garden rosemary to an indoor pot and continue to grow it over the winter.
When to Transplant Rosemary
The best time for transplanting rosemary is in the late fall or early winter, at least two weeks before the first expected frost of the season. Before digging, makes sure the soil is damp, as this will make digging easier and minimize stress to the plant. During dry weather, run a hose lightly for about 15 minutes, then wait 30 more minutes for the ground around the rosemary to become damp.
Before Getting Started
Carefully look over your clump of rosemary and find a large portion that looks full and hardy, but one without thick stems. If the plant is too old, it will be mostly woody stem without much greenery; this is not a good choice for indoor planting. Instead, choose a large healthy section that is mostly fresh and leafy.
Closely examine each stem and avoid sections that are hiding bugs or harboring disease.
Equipment / Tools
- Shovel or trowel
- Rosemary plant
- Planting pot
- Cactus/ succulent potting mix
- Drainage pan
Clear the Ground
Before starting to dig, clear away mulch and debris from around the base of the herb. This helps to ensure you do not add any hidden insects to the pot when transplanting. Clearing the area also allows you to look at the entire plant and evaluate how worthwhile it is to transplant. Again, if it seems overgrown and woody, it may make more sense to just take cuttings and root them instead of transplanting the entire plant.
Loosen the Soil
Use a shovel or garden fork to form a deep, circular perimeter in the soil around the plant, roughly the same diameter as the spread of the stems. Typically, a rosemary plant has a root structure that is nearly the same size as the above-ground growth, and the fewer roots you cut, the less stress the plant will experience when you transplant it. Gently rock the shovel or fork each time you sink it into the soil; this will make it easier to extract the plant, roots and all.
Lift Out the Plant and Rootball
Once you have loosened the soil around the entire rosemary plant, you can then lift the entire rootball from the ground with ease. If you find that lifting the plant is difficult or you hear a lot of roots ripping, go back and loosen the soil more before trying to lift the root ball again.
Move the Plant
Immediately transfer the rosemary plant into a bucket for moving. It is best to keep as much soil intact as possible. The bucket will prevent the roots from becoming exposed while you get ready to transplant the plant into a winter container.
Pot the Rosemary Plant
Move your rosemary plant into a container spacious enough and deep enough to hold the entire rootball. Fill the spaces around the roots with a well-draining potting mix designed for cacti and succulents. Water the soil as you fill the pot with potting mix, to settle the soil and eliminate air pockets.
When the rosemary has been potted, place it in a tray containing a layer of gravel. This tray will provide drainage for the plant and prevent the roots from becoming too soggy. For the first week or so, acclimate your plant by bringing it indoors during the night, but move it back outdoors during the daytime. When the daytime temperatures are no longer reaching at least 55 degrees Fahrenheit, it's time for the plant to come indoors permanently for the winter.
Grow your potted rosemary in the sunniest, brightest indoor location you can find. If the plant begins to struggle, you may need to add fluorescent lighting. Water once every few weeks, but make sure the tray always has water in it. In the spring, the plant can be moved outdoors to continue growing as a potted patio specimen or transplanted again back into the garden.
McGowan, Alice, and McGowan, Brian. Bulbs in The Basement, Geraniums on The Windowsill: How to Grow and Overwinter 165 Tender Plants. Storey Pub., 2008