I've lost entire vintages overnight.
Here's what winter survival looks like when you farm wine in the highest elevation wine region in North America.
Winter is the most important and least controlla...
Making sure they get inoculated with arbuscular mycorrhizal fungi helps a lot with cold so I hope your dad did that when he put them in. Sprays like seaweed and the biodynamic valerian prep help too but like you say the timing can be pain and sudden drops like that are always going to be a challenge. Goodluck.