Spring cold is bad for plants at their northern limits

The cold variable weather we've been having this year and for a few past is wreaking havoc with the early-flowering plants at the northern end of their geographic range.  We have a few that are (mostly) surviving but not flowering.  For example, Edgeworthia chrysantha grows well enough but for the past two to three years has not flowered well because of the frosts.  The Daphne odora are similar although they have suffered a bit more with plant die-back, again especially in the past few years.  The Stachyura praecox is a bit of a mixed bag.  Some of the later flowers are OK but the earliest have been damaged by the frost.  In all cases, the issue appears to be lengthening days causing the plants to come out of dormancy and warm early days causing the plants to flower and the blooms then being whacked by hard frosts.

Our second evergreen Magnolia virginiana lost its top this spring during the heavy wet snow we had a few weeks ago.

Maybe this isn't such a good idea...