December 2010 was the coldest December on record in many parts of Northern Ireland with extreme frosts on many occasions. The West of the province saw the lowest temperatures and Castlederg broke the all time low on several occasions, finally setting a new record low of -18.6C (-1.5F) on 23rd December.
Here, in South Belfast, adjacent to the frost pocket of the Lagan Valley, frosts were also prolonged and severe falling to -11/-12C (10F) on several nights. Downtown Belfast and areas near the sea or outside of valley frost pockets, still saw lows of -9C.
Damage to tender plants was not immediately apparent and it was some weeks after the New Year thaw before it became clear that the numerous Cordylines which had been planted in gardens all across NI were slowly collapsing en masse!
Now, at the end of March 2011, it is possible to have a clearer idea of the full extent of damage in my own garden and it is not good news. Definite losses include Chamaerops humilis, Beschornaria yuccoides, Dicksonia antarctica, Astelia Silver Spear, Musa basjoo (even though they were protected) Callistemon, Aloe striatula, most Fascicularia bicolor, all agaves - including 2 Agave parryii which had previously survived -10C. (The picture above was taken in February but the plant continued to rot and is now mush!)
Smaller Agaves which I had been bringing on in pots in the cold greenhouse also suffered badly but it was interesting to see the effect on some species which had been promoted as ideal for our climate. First to collapse completely were Agave montana and it was a pretty comprehensive wipeout! Next came A. protamericana and desertii (although a few of the latter look like they may survive). A parryii ('giant' form) were untouched, at least until a cat got into the greenhouse and knocked several over! I am pleased that young plants of A. ovatifolia also performed well. They are fast growing compared to other species and on this evidence they may be albe to go outside. Two A. scabra plants also survived untouched.
Survivors included Trachycarpus fortunei and wagnerianus (but see the next post) although not without some leaf burn. I am hopeful that my Jubea Chilensis might survive - I threw several blankets over it before the extreme frosts, but it still suffered considerable leaf burn. Surprisingly many of the low growing Delosperma succulents survived - perhaps helped by several inches of snow cover for most of December.