Late December of 2017 through early January of 2018 saw record cold in Maine and other parts of the Norteast. The nearest National Weather Service station is about 5 miles away and their records are as follows: 12-25 +3, 12-26 0, 12-27 -9, 12-28 -4, 12-29 -16, 12-30 -16, 12-31 -13, 1-1 -18, 1-2 -11, 1-3 -8, 1-4 +1, 1-5 0. With temperatures like these lasting for an extended period, I anticipated heavy losses, especially among the species. I was happily mistaken.

Among the big leaf species, fictolacteum was the most severely damaged but is currently putting out new growth. Sutchuense and calophytum - both between 3 and 4 feet tall - were not at all damaged. Neither was asterochnum although this smaller plant was beneath a good depth of snow. All of these were protected with teepee style frameworks covered with landscape fabric. This is necessary even in mild winters to protect the large leaves from wind damage. Snow depth during this period was 10 to 12 inches, so the above the snow line growth was fully exposed to the cold.

Other species, some with wind barriers and some without, that came through the winter with no or minimal damage included insigne, bathyphyllum, pseudochrysanthum, adenopodum, adenogynum, roxieanum v. orenestes, balfourianum, paradoxum, taliense, russatum, wasonii, souliei

I don't really have any ready explanation for how species rated as hardy to 0 or -10 withstood prolonged temperatures far below that range. Certainly the snow cover, even though it was not deep enough to cover all the foliage of most of them, was a factor. The fact that this cold arrived relatively late after plants were fully dormant is another factor. Last summer was extremely dry and October was exceptionally warm. This meant that watering and natural rainfall continued later than usual. The hardiness ratings may be overly conservative although it's never wise to generalize after a single experience.

There were fatalities: thayerianum, pseudotrichum and fortunei (which has never done well for me).

Hybrids mirrored my experience with the species. The ultra hardy David Leach ones did fine as expected. Others, like several of the Hachmann hybrids, were fully exposed to the cold but suffered very little damage and bloomed well. Low growing hybrids, many of them originating in the UK or on West coast, were fine beneath the snow.