Duration, duration, duration

Garden at the end of January

When I give talks about growing hardy palms or other marginally hardy plants, one of my talking points is "location, location, location".  My point is that I live in a city, so I benefit from an urban heat island that keeps me quite a bit warmer than the surrounding suburbs.  In addition, there are microclimates within the city, and even within our own yards, that can add or subtract up to a half zone of hardiness.  For example, my property is on a north-facing slope that receives no direct sun from mid-November to mid-January; overnight low temperatures in my yard are nearly always several degrees colder than the "official" temperatures for Washington, DC as recorded at Washington National Airport (which, ironically, is not even in DC!).  This morning the official low at DCA was 16 degrees, but at 4:00 am the temperature in my yard was 12 degrees.

The saga of the Scottish Rite palms

Scottish Rite Temple, December 2009 (Photo: Kenneth Fletcher)

In summer 2009 an interesting thing happened.  The Scottish Rite Temple on 16th Street in Washington, DC--just blocks from where I live--had new landscaping installed that included two good-sized palm trees flanking the front entrance.  The palms were palmettos, Sabal palmetto, a species native to the southeastern USA.  This had various palm growers scratching our heads; were they meant to be permanent?  If so, they were a poor choice as this species isn't hardy in zone 7, and planting so late in the growing season would give them insufficient time to establish themselves before winter.  But if they were meant to be temporary plantings, it seemed rather expensive and extravagant.