On the line: over­win­ter­ing rose­mary

Daily Local News (West Chester, PA) - - LIVING - Pam Bax­ter From the Ground Up

On Thanks­giv­ing Day I re­ceived a query from my friend Natalie. “Hi, Pam! How should I win­ter my rose­mary plants? In­side, out­side — I’ve read both. (I’m hop­ing out­side, as I don’t have a lot of sunny win­dow spots.) They’re in pots, and sit out­side my west-fac­ing kitchen door.”

This is a great ques­tion. With its woody stems and sturdy, nee­dle-like leaves, rose­mary looks like it should be able to eas­ily han­dle our mod­estly cold win­ters here in the Delaware Val­ley. How­ever, as I’ve ex­pe­ri­enced over the years, this is not the case. I replied to Natalie, “I don’t have great ad­vice. I have tried both ways (out­doors and in­doors) with in­dif­fer­ent re­sults. Kind of de­pends on how se­vere (cold) the win­ter is go­ing to get. Maybe a garage would be the best?” I also promised to learn more and get back to her.

A clue to rose­mary’s win­ter vul­ner­a­bil­ity is that it is na­tive to the Mediter­ranean re­gion, which — un­like our area — has hot, dry sum­mers and rel­a­tively warm, moist win­ters. (Much of Cal­i­for­nia’s coast has a sim­i­lar cli­mate, and you’ll com­monly find full hedges of rose­mary in gar­dens there.)

Rose­mary (Rose­mar­i­nus of­fic­i­nalis) is des­ig­nated as a “ten­der peren­nial” through USDA Har­di­ness Zone 7. Below Zone 7, it’s con­sid­ered to be an an­nual. The Delaware Val­ley is right on the edge of this Zone, with some of us po­ten­tially warm enough in Zone 7b (parts of Philadel­phia) and Zone 7a (Philadel­phia, Kennett Square), and some of us too cold in Zone 6b (West Ch­ester, Phoenixville). In­ex­pli­ca­bly, Pottstown, farther north than Phoenixville and West Ch­ester, is in Zone 7a.

Note: “Below Zone 7” is a ge­o­graphic, not nu­meric ref­er­ence. As you go farther south on the United States map, the num­bers go up. (The south­ern tip of Florida is Zone 10.) Below Zone 7 takes us north on the map. The Zones are based on the cold­est po­ten­tial tem­per­a­ture for a re­gion, e.g., Zone 7b (5 to 10 de­grees F.), Zone 7a (0 to 5 de­grees F.), Zone 6b (-5 to 0 de­grees F.)

The Satur­day af­ter Thanks­giv­ing, still think­ing about Nat-

alie’s ques­tion, I hap­pened to be in my car just in time to hear that “You Bet Your Gar­den” host Mike

McGrath would be ad­dress­ing this very ques­tion later that morn­ing. I couldn’t lis­ten then, but found the

pod­cast and a full ar­ti­cle (see below).

In his typ­i­cal blunt fash­ion, McGrath goes right to the heart of the mat­ter: “Rose­mary just plain dies if left out­doors over the win­ter in re­gions roughly north of Washington, D.C. It can’t come back from its roots like a fig. And it doesn’t mat­ter how big or old the rose­mary plant is.”

Hav­ing said that, McGrath sug­gests that drainage may be a big­ger is­sue than the cold. “Like its cousin laven­der, rose­mary can’t stand wa­ter­logged soil. And with­out sum­mer heat to help dry them out, north­ern soils stay pretty damp over most win­ters.” I would add that with our typ­i­cal pat­tern of snow-then-melt-then-snow, over semi-frozen earth, the soil here may hold more wa­ter in the win­ter than in the sum­mer.

What about bring­ing rose­mary in­doors for the win­ter? McGrath says that pot­ted rose­mary plants may be out­side any time that the day­time tem­per­a­ture is 40 de­grees or above; in fact, they’d pre­fer to be out­doors. Just bring them back in­doors overnight if it’s go­ing to be re­ally cold.

If you get a pot­ted “Christ­mas” rose­mary, McGrath says that it’s im­por­tant to im­me­di­ately re­pot the plant into a larger con­tainer, us­ing “the loos­est, light­est bagged pot­ting soil you can find.”

Read all of McGrath’s rose­mary-win­ter­ing tips at http://www.gar­den­salive. com/prod­uct/ybyg-turn­ingchrist­mas-rose­mary-into-afull-time-plant.

To check your har­di­ness zone, go to http://www. plantmaps.com/list-of-har­di­ness-zones-for-penn­syl­va­nia-cities.php.

If you want your in­ground rose­mary to make it through the win­ter, you might ex­per­i­ment with R. of­fic­i­nalis “Arp,” re­put­edly hardy to Zone 5.


A plant­ing of rose­mary spills over a gar­den wall in Berke­ley, Calif.

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