I plan to buy a sheared rosemary plant to use as a tabletop Christmas tree. How should I care for it so it will stay healthy enough to transplant to my garden in the spring? Will I need to trim it to keep it in the shape of a tree?
You are not alone in your interest in adopting a rosemary Christmas tree. They are readily available at garden centers, discount stores and supermarkets. Unfortunately, plants often do not receive attentive care on their journey to the store, so shop carefully. The leaves may appear deceptively healthy, because plants often are sprayed with anti-transpirants as they are prepared for market. If possible, check the roots to make sure they aren’t dead. Dead roots are either black with rot or as dry as straw. Healthy rosemary roots are woody and brown, and many of them are located in the top three inches of soil.
As you select your plant, also choose an 8-inch pot that has several drainage holes in the bottom. A wide, stocky pot, such as an azalea pot, is ideal. Rosemary needs lots of horizontal root space, but you can use a lean potting soil, such as bagged topsoil, as you pot it up. Repot your rosemary tree into its new home. Now, you can decorate the plant, using a light hand. Try making your own featherweight decorations — stars made from metallic gift wrap, painted bowtie pasta hung with thread, or tiny candy canes made of pipe cleaner. You also can try braiding together three pieces of narrow ribbon to make a garland.
Make sure not to give potted rosemary trees too much water. Learn to judge the moisture level in the pot by checking its weight, and don’t be afraid to let it become nearly dry between waterings. If you think your plant is parched, look for these symptoms: bluish leaf color and slight wilting of the tips of new leaves. Step up watering a bit, but do not feed your plant. Rosemary grows little in winter, so fertilizer is not necessary.
Mark Langan, owner of Mulberry Creek Herb Farm in Huron, Ohio, with his wife, Karen, shared several hard-learned tips for keeping a rosemary Christmas tree beyond its first season. A few years ago, when the Langans’ toddler broke the latch on their kitchen window, they watched as a rosemary plant exposed to cold drafts grew beautifully, while the ones in their warm greenhouse struggled with powdery mildew. Mark lowered the temperature in the greenhouse to around 50 degrees, and the rosemary plants there responded beautifully. The lesson here is to keep your plant in a cool spot as much as you can. On mild winter days when the temperature is above 40 degrees, set it outside for the day and bring it back in at night.
The Langans have a healthy rosemary tree that’s 6 years old, but each summer they take the plant out of its pot and plant it in the garden (Mark thinks a large 24-inch half barrel would make a good alternative). Either way, it’s important to let the plant have all the root space it needs from May to September. During that time, you will need to trim the plant every four to six weeks to help it keep its shape. Instead of using scissors or pruning shears, the Langans shape their plants by bending the stems over the blade of a sharp knife. That way, the stem is cut but leaves are left intact to cover the stub.
The next step sounds harsh, but it works. At about the time of your first fall frost, give the plant a last perfect haircut, and then dig it up and cut off as many roots as necessary to make the root ball fit into an 8- or 10-inch pot. Give the plant a little water, wish it well, and leave it outside until temperatures below 30 degrees are expected. When you bring it indoors, keep it in a cool room where it will receive plenty of light from a south or west window.
One of the stories that’s made rosemary a traditional Christmas herb tells how Mary washed her baby’s blankets and then laid them on a rosemary bush to dry. After she gathered them up, the rosemary bush bloomed for the first time. If you follow the steps I’ve outlined here, your plant should bloom each spring, too, and be part of your holidays for several seasons to come.
Barbara Pleasant is a contributing editor to The Herb Companion and author of several books about gardening, including The Whole Herb (Square One, 2004).