PBS website contact:Lycoris
Jane McGary (Thu, 13 Sep 2018 09:46:59 PDT)

After I mentioned that Lycoris did poorly for me in western Oregon, Val
in inland northern California asked:

Jane, would you please write about why Lycoris does badly in the far
west? I had thought it was just Lycoris sprengeri that we couldn’t grow
and that it

Years ago, I was talking with author and nursery grower Sean Hogan and
mentioned that I couldn't succeed with some plants from Japan and the
eastern USA. I wondered if there was some factor they shared to which
the US Pacific coast region was inhospitable. His opinion was that the
different levels of atmospheric humidity in summer might be the cause.
In summer-dry regions, low humidity results in pronounced temperature
drops at night (commonly at least 20 degrees Fahrenheit, sometimes
more), whereas in moist-summer regions at low elevation, night cooling
is not to be so sharp. The cold nights might trigger dormancy and
interrupt the typical annual growth and flowering cycles of plants. It's
well known that some cultivars of daylily (Hemerocallis) will not flower
well, or at all, in the Pacific Northwest, but flower well east of the
Rocky Mountains. Temperature drop might be even sharper where Val lives
than it is here in a suburb of Portland, Oregon, since her area is both
drier and at higher elevation than mine. When I go to the east or
southeast USA in summer, I feel as if I'd stepped into a steam bath.

This doesn't occur with all plants from humid-summer regions. Japanese
lilies do well here, as do a number of East Asian genera in the lily
family (broadly speaking; is it Liliales now?). Perhaps it's more common
in summer-flowering plants than in spring-flowering ones? On the other
hand, Kirengeshoma (Hydrangeaceae) is flowering well in my garden at the
moment, right on schedule. It can even be affected by microclimate: I
notice that only a quarter-mile from here East Asian plants and eastern
American trilliums flourish much more than in my garden, which is on a
ridge, and that garden is in a moist, sheltered site that slopes down to
a permanent stream, presumably having more humidity at all times. On the
other hand, some plants do well here but are difficult in the east
because they succumb to diseases promoted by summer moisture (e.g.,
Dianthus).

"Hardiness" and "zone ratings" are not a dependable guide to how well a
plant will grow and, especially, flower in a given place. Factors that
aren't readily available as data, such as seasonal humidity and rainfall
cycles, have to be considered too.

Jane McGary, Portland, Oregon, USA
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