Southeastern PA in the US doesn't see much Poncirus damage in the spring. Prunus cultivars often suffer from freeze damage at time of bloom. Last year citranges began growth in the very beginning of May with no new damage at that point. The northern US is entering a period of unusually cold weather at present and I expect all late growth on both Poncirus as well as Poncirus hybrids to be damaged, or destroyed. Our fall was quite moderate until recently. The forecast low temperature for next week is 16 degrees F (-8.8 C). This is no problem in 6-8 weeks, but is a bit harsh this early in the season.