Rosemary, which famously stands for remembrance, often is sold as topiary this time of year—usually pruned into a Christmas tree-like shape. Actually, the use of this herb as a Christmas decoration is far from new, since 17th century poet Robert Herrick referred to it in a poem which was, oddly enough, about Candlemas Eve (February 1).
"Down with the rosemary and so," he wrote. "Down with the bays and mistletoe,/ Down with the holly, ivy all/ Wherewith ye deck the Christmas hall." Apparently, superstition forbade Christmas greens being left up into the next holiday (literally “holy day”). Not to mention that they would have been doing some major dropping of dry needles and leaves by then!
Speaking of dropping needles, rosemary (Salvia rosemarinus) can be difficult to keep alive indoors over winter, not because it is a tropical plant but because it is an almost perennial one—generally hardy to USDA zone 7 with the toughest cultivar, ‘Arp,’ reportedly capable of overwintering outdoors in zone 6. And hardy plants generally don’t do well indoors due to their need for chilly winter temperatures.
Since those of us to the north of zone 6 will need to keep rosemary “housebound” until spring, the fact that its species name rosemarinus means “dew of the sea” should give us some clues as to its preferences. Native to the Mediterranean area, it grows in sandy soil, while frequently sprayed by wind-blown sea water. So, it likes its “feet” dry and its foliage dewy.
Therefore, once the holiday has passed, you’ll want to remove and discard its moisture retaining pot wrapping and check the bottom of the pot to make sure it has plenty of drainage holes. Then you can place the plant atop a humidity tray in the brightest and chilliest position available in your home, well away from any heat sources and where it receives at least 6 hours of sunlight per day.
Because it originated in climates which experience cool but not arctic conditions in winter, rosemary prefers daytime temperatures between 60 and 65 degrees during that time, with nighttime ones dropping as low as 40 to 50 degrees. That will be hard to manage in your living room, but a sunny position in an unheated attached garage or sunporch might work. A greenhouse would, of course, be even better, but remains a dream for most of us!
I grew rosemary beneath a grow light in a chilly back room once, which worked well enough that the plant actually bloomed there—something it never does outdoors here in zone 5. But that room definitely was cooler and airier than the rest of the house.
Such lower temperatures help raise humidity, though you may still want to mist your rosemary frequently to approximate its native conditions. To avoid the plant’s soil becoming soggy, wait until that soil is dry an inch or two down to water the plant and discard any water that remains in the pot saucer afterward.
Rosemary for a Season and Seasoning
Of course, if you prefer easier houseplants, you always could just keep the plant until the end of the holiday season before you hang it out ...er, up, to dry and use its leaves as a spice instead. But, if you keep in mind rosemary’s preferences, your plant may just make it to Candlemas—and beyond!
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