I couldn't find a better spot to post this on the forum, so here it goes. After hours spent on googling, I couldn't find definitive answers to these questions, so I hope someone will be able to answer them here.
1. I know that a low dew point can be an indicator of frost if the air temperature is near freezing. As far as I understood, the harmful ice crystals form before the dew appears in such conditions. I also know that there's frozen dew, which happens when the dew forms first and then freezes. My question is - is frozen dew harmful to frost sensitive plants?
2. Can frost ever form in rainy conditions, where the climate is such that the daily low falls a bit bellow freezing for a few hours only two or three times per year on average?
3. Where I intend to grow my subtropical plants, something looking like a white powder occasionally appears on the grass in winter mornings, but it's always only at ground level. Assuming that this is frost, can it harm fruit trees and if yes, will mulching around the base of the tree be sufficient to protect them?