Southwest France is mostly zone 8b and, maybe due to global warming, many winters are actually more like zone 9 winters. Due to that, gardeners are tempted to plant tender maples in the ground. Alas, from time to time (every 20 years or so) a harsh cold snap puts the clock back to where it belongs. This past winter was one of those and the attached picture shows the recordings at my garden outside Toulouse. Thirteen days below freezing, with the ground frozen down to 15 cm, damaged heavily all evergreen maples (and many other evergreen plants). In spite of that only one maple was killed, Acer oblongum. Another one was heavily damaged, but survived: Acer coriaceifolium. The maples: Acer laevigatum, acer sikkimense, acer obtusifolium and acer discolor lost all their leaves but leafed out in the spring without any damage. The deciduous tender maples: Acer skutchii, acer calcaratum, acer hyrcanum ssp Reginae-Amaliae, acer robustum, acer pentaphyllum and acer buergerianum ssp formosanum, have all leafed out without any trace of damage. I have many palmatums/japonicums/shirasawanums in pots of all sizes and materials and I left them outside. The palmatums and japonicums did not seem to suffer but I have lost 50% of the shirasawanums and several matsumurae. I hope this info will be useful to other maples enthusiasts. Gomero
Thanks for posting, interesting info. I was surprised to see that the shirasawanum and matsumurae fared worse than palmatum and japonicum in containers. I may have lost a matsumurae this winter, initially I hadn't considered cold as a potential cause, but I will reconsider in light of this. A couple of questions; were the 13 days consecutive or is that 13 days over the whole winter? [edit: I think maybe the 13 days represents a single cold spell, but not 100% sure I am reading it right.] What month(s) were the cold temps experienced during? Were the pentaphyllum that survived in ground or potted?
Sorry to hear you've had more losses Gomero,but it's good of you to take time to list and share your findings.Whilst I only have Japanese maples it's interesting to know the Shirasawanums are the least hardy.I'm sure your experiences will serve to reassure many and be a useful warning for others.
Since the temperatures given for hardiness zones are based upon average lows over multiple winters there really is no so such thing as an individual winter corresponding to a specific zone. A Zone 8 winter can bottom out at 5(F) or 25, both are still Zone 8 winters.
In fact, and it is a coincidence, the days listed corresponded to 13 consecutive calendar days in February 2012. So day 1 was February 1st, day 2 February 2nd, etc. All the species quoted were in the ground with a thick layer of dead leaves giving some protection to the roots. Also on February 4th we had 5 cm of snowfall that, evidently, remained in the ground for the period. Potted maples did not benefit from this and were those that experienced the harshest conditions. We all know that,........ we also know that 2+2 = 4 Gomero
Thanks for the information Gomero. You keep careful records! We saw similar temperatures here; a local veg grower in the village reported -18 but his location is much lower and significantly colder than here. I had very significant damage to A. shirasawanum ssp. shirasawanum which had been a very healthy and beautiful small tree. The other shirasawanums in pots still I brought under shelter during the very cold period. A. cordatum did not mind the cold. I have only just planted out A. discolor, my previous on was eaten by deer. But it was very hardy, surviving (I think it was) 2008/2009 which killed many plants like pectinatums. Interesting about laevigatum, I am trying to grow it from seed if the mice didn't eat them all. How far back does your data go? I just got a fun weather station for my birthday, but unfortunately it doesn't log data to the computer. -E
>many winters are actually more like zone 9 winters< >We all know that,........ we also know that 2+2 = 4< Many people mistakenly think if they get one low within the average range used to indicate a zone that low puts them in that zone, and proceed from there. This is demonstrated on the internet over and over. Nursery catalogs and labels display the same mistake, with readers being told plants are hardy to say, Zone 7 that are liable to be damaged or killed by fairly typical temperatures in the zone rather than more extreme ones.
Hmmm. I always thought Shirasawanums were as cold hardy or even hardier than Palmatums? Maybe I'm getting that confused with Japonicums.
Shirasawanums is actually hardier than palmatums, but not as hardy as japonicums. But the difference is not large, at least in the climate where I live. Maybe Shirasawanums roots are more vulnerable for the repeated freezing and smelting that can be when sun is hitting the pot in daytime and the cold come back at night.
I did lose some palmatums in pots as well, about 20% . With the shirasawanums (I lost 80% of those in pots), one must be cautious since: Many 'shirasawanum' cultivars are actually shirasawanum x palmatums hybrids. Those cultivars are grafted and the rootstock could very likely be palmatum Therefore I do not think that my experience can be used to draw conclusions on the A. shirasawanum hardiness in pots. For the period under consideration, the pots were solid frozen throughout. No sun hitting, no melting. Gomero
hi gomero thanks for the useful records what about the shirasawanum in the ground ? i did not know that shirasawanum were so lightly cold tolerant in pots we experienced the same cold winter here near bordeaux, specially in my garden which is by the river and in the forest (-15.4 was the minima). Since know, i just see more than normal dieback on little branches (mikawa yatsubusa, crimson queen and okagami suffer the most) but no losses all my maples are in the ground
