Cool & cold weather plants care is more-or-less routine hereabouts .... I'm in about 5a here in South-Central Ontario (25 or so miles north of Lake Ontario) - Over the recent few days we've had two similar days that were what I call '4 Season Days' (NOT unusual hereabouts) ... Within 24 hours you get a bit of all 4 seasons tossed at you ... We've had (yesterday) two snowing incidents the same day of 'White-Out' snow conditions. High winds. Snow traveling parallel to the ground (Blizzard-like) The early morning incident leaving over an inch of snow on the ground in about 10-15 minutes. By afternoon almost ALL that snow was gone - GONE! - Melted due to the temperature rise with the bright sunny calm conditions. (!!)
Even though Canada works with metric & Celsius systems, I grew up and still function most frequently, with Fahrenheit for temperatures. At about 5:00 AM we were at a wintery 22F - our birdbath was frozen - but by mid afternoon we had risen to a pleasant spring-like 46F (A robin was bathing in that same birdbath!). Kinda normal variations this time of year.
Our springtime 'Last-Frost-Date' traditionally has been considered to be late May - May 24th was generally accepted as the safe-to-plant-most-things-date. Nowadays that has backed up to perhaps as early as mid-may (Even earlier?) Because you would go berserk trying to cope with our weather variations I did not cover anything. Everything growing outdoors around here either copes - or croaks.
Known hardy daylilies in the ground are usually OK - especially if they've had a full growing season to develop and to adjust (Spring or early summer planted) Known hardy cultivars in pots and exposed to a full winter of freeze-thaw periods, do only fair to poor overall. If put up against a house wall (Usually west here) and covered with straw or a tarp they can survive quite well. (Drying out is the problem however) This past winter I lost - so far anyway - STEPHANIE RETURNS (Same plant 'In-Ground' is OK.) ... Exactly the same with JANICE BROWN.
We usually have very good snow-cover hereabouts. I've had up to 2 feet of snow-cover for most of the winter sometimes, but most years count on 10-12 inches over the full season. Snow-cover DOES work here for me. Seedlings left in pots over the winter (I procrastinate!) survive well with good snow-cover .... BUT I've lost as many as 1/2 if we have an 'exposed' lengthy winter period. (Same seedlings that were planted into beds did - generally do so - quite well.
Bottom line: - In this 'Great-White-North' work with known hardy cultivars. Avoid pots for over wintering. Hope for snow cover. Be prepared for occasional losses. Cultivars still in pots over the winter need to be watered lightly during thaw periods. Never give up ....
