mike wrote

It has been above freezing for several weeks now and everything is
blooming and leafing out. But tonight it is going to get down to 26.

I have hostas, lots of irises, daylilly, roses, peonies and tons of
other perennials coming out of the ground and leafing back out. I do
not have much to cover my plants and I covered my roses first - what
types of things would be most likely to be killed? Or will it just
kill plants back and force them to come out again?

I was also concerned about my autumn olive which is blooming for the
first time. I assume it will kill the blooms and thus the fruit even
if no serious damage is done to the shrub itself. I hate late
freezes.

Even plants that habitually survive cold winters may be damaged by a
late freeze after they have begun to put out new spring growth. I
still mourn a pretty little rose that had leafed out beautifully and
then succumbed to a surprise spring blizzard (I *did* wrap it up, but
the covering blew away). Daylilies and Iris are pretty tough. In 20
years, I've never had Hostas damaged by crazy weather (zone 7b or 8).
As the newsies say, "only time will tell." If the plants are
well-established, your yield of growth/blossoms/fruit may be affected
for this year, but the plants you mention (my rose was *very* small)
will probably survive a short cold snap. Best wishes.