tim, did not mean to sound like all doom and gloom. not a lot of positive surprises...this winter separated the men from the boys so to speak. agave harvardiana is a keeper...no damage. agave ovatifolia also very little damage, a. gracilipes, a. neomexicana uscathed. i do not have one but surprisingly loquats came through intact, never any fruit this far north but grown for their very nice leaves.
my faxonianas look similar to your least damaged yuccas. they are not ideally suited to this area. already some damage from this weeks frost noticeable. i will be glad when spring truly arrives. the thing most surprising is the amount of damage your yuccas experienced even under plastic! i have lived here all my life and similar scenarios have happened before. these only happen years apart, thankfully. randy