The frosts were harder at my family home in the Co Derry countryside, where I suspect lows were closer to the Castlederg figures - probably in the -16C to -18C range.
Even Trachycarpus fortunei (pictured) succumbed here. The centre spears of this plant pulled out with only a slight tug and it looks very much as though 3 of the 4 plants in the garden are dead. The fourth is the tallest (15ft) and is planted on a slope, close to an even taller hedge, which may have given it some protection.
Musa basjoo and cordylines were also destroyed here and large clumps of New Zealand flax (Phormium tenax) have collapsed. There is little sign of life, even in the more robust green form (pictured below)