This calculator is based on the data collected from 48 citrus trees that have been taste tested as well as grown on our property so their leaves could be tasted and counted. Our original idea was to incorporate leaf type into the prediction model (percentage of leaves that were unifoliate or bifoliate), since this would be a normal, practical test someone might conduct. However, the data showed there was no meaningful correlation between leaf type and fruit quality when controlling for true citrus vs. hybrids with Poncirus. Believe it or not, this was also true for predicting cold hardiness! If we do not control for true citrus, there is otherwise a strong correlation between leaf type and fruit quality/cold hardiness.
We must acknowledge that our small sample size is a limitation, and we cannot guarantee the same effects across a larger sample size. However, the link between cold hardiness and reduced fruit quality is undeniable! Unfortunately, cold hardy citrus breeding will always be limited by this fact, but there is promise in the meaningful overlap that exists between fruit quality and hardiness ratings.
