Hi, I would wait untill May 24 weekend and plant the hydrangeas outside then, this is usually our time when frost is over. They won't rebloom this year however with the proper maintenance they will bloom the following year

I've seen several hydrangeas today in several flower shops. One seller told me they were hardy but I had my doubts. Later at another location, I spotted the same kinds of plants and was told these weren't hardy to our locations. Closer inspection to the plant tags confirmed this. They could still be treated like annuals. So the one in Costco, did you see a plant tag and is there a description about the average temperatures it will take?

ianna, as you know i leave in Brampton and i have blue nikko and endless summer hydrangeas and they have to be protected during winter months otherwise they will not flower although they have "nick-name" as hardier hydrangeas?

Those bright blue and pink hot house hydrangeas that are sold at Easter and Mother's Day are not hardy. The Pegee type are hardy and there are a few others that are, as well, but I believe they all have white or off-white flowers.

Here is a link that might be useful: My Country DIY Blog

I have planted the kind of hydrange a that is sold at
Easter and have had them come back for several years. I gave one of the potted blue ones to a friend when her husband died and it has been blooming in her garde n for over five years.

radovan, forgive my very delayed response. I didn't see your question till today. Nikkos and Endless summer are fine. I was able to grow Nikkos in my previous home in a sheltered spot. This was in a zone 5 area. The ones we see in grocery stores and flower shops are mostly not hardy. These are the ones to avoid. However this does not mean all the hydrangeas being sold at this time are not hardy. Look carefully at the tags. Without it, treat it as not hardy. Greylady - I am describing the hydrangeas I've seen so far which have come with clear information on hardiness. So I cannot comment on the plant you got many years back.