Garden centers, big box retailers and even grocery stores are filling up with holiday plants, and the ones I’m drawn to are rosemaries shaped into classic topiary forms and cone-shaped Christmas trees.
Rosemaries are actually evergreen shrubs that originated in the rocky sites and scrub of the Mediterranean region. They grow wild in the south of France where the winters are cold, damp and very windy and the summers are hot and dry.
When grown in the ground, rosemary sends its roots deep into the soil to search for moisture so it can withstand dry conditions. But when grown in a pot, the plant soon becomes pot bound and the roots suck up the moisture so quickly the fast-draining soil dries out.
Unfortunately, the rosemary does not make a good houseplant for those of us who live in Michigan, but here are some tips I use to keep them alive until spring when they can go out in the garden.
The late Tom De Baggio, a professional herb grower and nationally known author, recommended the soil of a potted rosemary be kept slightly moist and not allowed to dry down causing the plant to wilt. Older herb books suggest letting the soil dry and then water. But I can tell you from experience, a dry rosemary is a dead rosemary. So if you’re growing rosemary indoors, take care to keep it watered.
Rosemary is a sun lover and outdoors it needs at least six to eight hours of full sun daily to thrive. In winter, Michigan can go weeks without seeing the sun, so even when these plants are placed in south-facing windows they can struggle. The best way to provide the proper light is to grow them under a grow light placed 4 to 6 inches above the plant for 14 hours a day. When entertaining you can move the plant to center stage. A day or two in the shade won’t kill it.
Humidity is another big issue. When the furnace goes on the humidity in a house may drop to below desert levels. Misting is not the answer. Better to place the rosemary on a large tray filled with pebbles and water. Called pebble trays or humidity trays, there are videos on Youtube that show several ways to set them up. Pebble trays are also great for orchids and other houseplants.
Air circulation also helps to prevent powdery mildew, which can be an issue. I use a little clip-on fan that cost less than $10.
Nancy Szerlag is a master gardener and Metro Detroit freelance writer. Her column appears Fridays in Homestyle. To ask her a question go to Yardener.com and click on Ask Nancy. You can also read her previous columns at detroitnewscom/homestyle.