Frost in May in the regions with continental climate is not unusual. Two rather cold mornings and frost were enough to make this damage on Hosta 'Sum and Substance', Hosta plantaginea and Polygonum polymorphum. It was - 2°C! Luckily, only three most exposed Hostas suffered this damage. Actually, they got burnt by sun that came after the frost. Now I have to remove the damaged foliage. I know, they will sprout again but, what a pity!