GREEN PATCH
Question:
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?
Answer:
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).