COld tolerance of Alstroemeria, was Freezing bulbs: Duration vs. low temperature

I would like to hear about people's experiences with Alstroemeria
cold tolerance. I had many plants left outside unprotected since last
night's forecasted low of 33F by the National Weather Service was a
full 6 degrees off from reality (it was actually 27F).

I am an enthusiast of this genus and have traveled a lot to see them
in the wild, and have also grown a number of species from seed. My
previous garden is at 1600 feet (about 500 m) in the Oregon Cascades
foothills and routinely had winter lows around 16 F, sometimes
without snow cover. Even in the cold frames temperatures dipped to
about 20 F, and I feel that any plant that I grew for five years or
more can tolerate that temperature provided the foliage is reasonably
dry. I now have my plants either in the open rock garden or in raised
beds with a polycarb roof but no solid sides on the building.

Taxa that have done well for me in the open in both gardens are
Alstroemeria ligtu ssp. incarnata, A. ligtu ssp. simsii, A.
angustifolia, and of course A. aurea. Under cover I have grown A.
diluta, A. hookeri, A. umbellata, A. patagonica, A. magnifica, and A.
pallida. The only Brazilian species I've grown is A. isabellana,
which is being distributed as "Bomarea x Alstroemeria Fred Meyer".
(Thanks to Nhu Nguyen for clearing up the identity of this plant.)
It's in a rather sheltered corner in my present garden, which is in a
"banana belt" with lows the past week around 27 F, and it looks all
right so far. I don't grow A. pulchella (syn. A. psittacina) but it's
in some sheltered Portland gardens.

Hardiness in Alstroemeria should depend largely on the range of the
species. I haven't visited them in Peru or Brazil, but in Chile, the
center of distribution, there are a number of species limited to the
northern coast, and some of these are quite strictly coastal or even
beach plants (e.g., the popular A. pelegrina) while others get up
into the Coast Ranges and Central Valley where light frost can occur.
A gardener with a large cactus collection just east of the coast
range, in hills, told me he had lost a number of plants to frost a
few years before, for instance, and that the avocado groves had been
damaged. The A. ligtu subspecies mentioned above are Central Valley
natives and flourish in a large sand and gravel berm in my colder
garden (please buy the place, you can have the alstros!). Although
the "Ligtu hybrids" are unpopular with gardeners because of the way
they spread underground, I wouldn't want to be without these two
subspecies. Incarnata has a huge inflorescence of warm pink, and
simsii has narrow scarlet flowers.

Some other species occur in the central north of Chile and seem to be
tolerant of moderate frost. A. diluta and some subspecies of A.
hookeri are examples. Then there are Andean species such as A.
umbellata (very lovely plant) that grow in the snow zone and emerge
at snowmelt; I think of their habitat as similar to the central
California Sierra Nevada. A. aurea grows in conditions more similar
to those of the Pacific Northwest and is a notorious thug in gardens
(and indeed it carpets acres of woodland in nature, and I've seen it
thrusting up through blackberry thickets).

One species that I deeply covet, and have never been able to obtain,
is A. versicolor, which should be moderately hardy. If anyone has the
true plant (there is a lot of misnamed seed around), please let me know!

Jane McGary
Portland, Oregon, USA