Alstroemeria
Jane McGary via pbs (Sat, 30 Apr 2022 12:00:25 PDT)
I don't want to repeat my entire taped rant about hardiness "zones," so
will only note that when I lived near Estacada, in the Cascade
foothills, an area Marc Rosenblum probably knows, my home appeared to
sit on the line between Zone 8 and Zone 1 on the USDA map. Most winters
the low was around 15 F, but about every fourth winter, colder
temperatures occurred, the lowest being minus 6 F in the historic cold
snap of 1990-91, which killed even some native plants all along the
Pacific coast. My doubts expressed in an earlier post are admittedly
subjective, based on a lifetime (75 come this July) of observation from
central California to interior Alaska and 9 plant-hunting visits to
western and Andean South America, as well as 30+ years of optimistic,
experimental gardening. Unlike Hortus III and the RHS, I'm not using
statistical methods, but the book "How To Lie with Statistics" comes to
mind.
I do want to correct myself: when I wrote A. pulchella, I meant A.
psittacina, which Garak's post mentions. Also note his phrase "for
single nights," which may mean that the soil did not freeze to the depth
of the tubers or even the growing points. Like many other geophytes,
alstros can delve deeply. I once dug down to see how A. umbellata (a
snow-zone central Andean) grew, and it was underneath about 30 cm of
loose, dry talus and another 15 cm of fine, slightly moist sand (in
January, the dry southern midsummer). That leads to another topic, the
influence of rocky habitat in providing moisture to plants in arid
climates, where fog or dew condenses on the rocks and trickles down.
Whatever the books tell you, that is not "baking."
Jane McGary, Portland, Oregon, USA
On 4/29/2022 11:24 PM, Marc Rosenblum via pbs wrote:
Jane,
I estimated that most Alstromerias have a hardiness threshold of about
0 F [-18 C].
Garak's -11C falls well above that threshold. I based my estimate on
Sunset, L.H. Bailey's Hortus III, and the RHS garden Plant Index.
On 4/29/2022 8:53 PM, Garak via pbs wrote:
I can confirm that Ligtu hybrids, psittacinas and modern
horticultural hybrids can tolerate unprotected, snowless frost of
-11°C for single nights. Unlike the Ligtus, modern hybrids will lose
overground growth to late frosts, but usually return soon after. I
agree that my mixed winter climate is far more difficult for them
than true continental climate would be. The psittacina actually has
more problems with my dry summers, it's a really thirsty plant.
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