Hippeastrum species - low temperatures
Lee Poulsen (Mon, 30 Apr 2007 11:39:11 PDT)

Yes, I have experience with Hipps and low temperatures (such as the
ones you ask about). As you probably know, California, in particular
southern California, had a fairly severe freeze for our climate. Many
locations, even close to the ocean saw temperatures below freezing on
one or more mornings in January. Several nurseries in northern San
Diego County that were only about 3 miles away from the ocean measured
lows of mid-20s F for four mornings in a row. I even saw frozen leaves
on plants in beachside neighborhoods in San Diego, which is one of the
few USDA zone 11 locations in mainland USA. It was a severe radiation
freeze with zero air movement in many locations leading to very small
microclimates (nanoclimates?) just about everywhere. I just heard from
several growers of Plumeria in Orange County who had them killed on one
side of their house and untouched on another side of their house. Even
at my house, my main exposed outdoor thermometer read 26 deg F. on the
coldest morning. Nevertheless, in my sizable side yard (where I grow a
lot of things since it gets the cooler morning sun), I think the
temperature only reached maybe 30 or 31 deg. F. Nothing I had there,
including seedlings showed any indication of freezing weather at all.
Clivias in my backyard (where my main thermometer is located) had
considerable leaf damage, while 6-month-old Clivia seedlings in the
sideyard acted as if nothing happened. That is also where I had all my
mature Hippeastrums as well as some 2 year old Hipp. seedlings. Even
though I tried to protect most of them from winter moisture, since
we're having a record-breaking low-rainfall year (3 inches total for
the year), the Hipps have been kept dry all winter. Even so, 2/3 of
them never lost their leaves. And none of the leaves were frozen on any
of the Hipps that had them. All of them appear to have survived the
freeze without any signs that they even cared. And even the species
that I worry about and keep in my unheated greenhouse experienced
temperatures in the high 30s on a couple of the mornings. (Nothing in
there was harmed or hurt. I have a few Episcias, but I've already
learned that they act like they've been frozen whenever they experience
temperatures in the low 40s F. So I always bring them inside before
then.)

So if this is helpful to you, then good. More likely this will confirm
to some how foolish I and a number of other plant hobbyists in Southern
California are in how and what we try to grow outside in this climate.

--Lee Poulsen
Pasadena, California, USDA Zone 10a

On Apr 30, 2007, at 9:37 AM, Stephen Putman wrote: