The hawthorn won't be blooming in profusion here before the end of May. Then the fields are a sight as so many of them are bordered with hedgerows containing a large proportion of hawthorn.

The blackthorns are coming into bloom now, but we don't have so many of them.

Old people here in Derry City have told me of hanging flowering gorse or whin (yellow flower) over their doors on May Day, to ward off evil.
Yesterday at set-dance class I asked about a half-dozen middle-aged people (40s/50s) and they don't remember the custom though some had also been told about it. Two of them volunteered the line:
"Don't cast off your clout Before May is out", pointing out that this refers to the May blossom and not to the month and therefore means about another month from now, when it's warm enough to dress lightly.