Hippeastrum species - low temperatures

Lee Poulsen wpoulsen@pacbell.net
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 

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:

> It has been a really peculiar weather year.
> I am wanting to get some of the bulb pots moved out of the greenhouse,
> but the weather still is too hot inside some days and too cold(?)
> outside some days.  Does anyone have experience with Hippeastrum 
> species
> and minimum night temperatures?  I have always used 50 F as a nominal
> minimum. Anybody have experience with, say, 45? or 40?

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