Although every winter is different, a good benchmark would be to do it after the average date of last frost has passed. But being an average, you could remove it 2-3 weeks afterwards if the average date turns out to be "too early" in some years.

Thanks very much for your response. However, I hope up in Canada we are dealing with much more cold-hearty varieties? At least I hope so. I was not anticipating waiting until May to take down that burlap.
Sometimes the leaves look totally folded up from the harsh winter, but this winter has been milder, so the leaves look more normal and I was hoping I might not have to wait a whole lot longer to uncover them.

It's always a difficult decision in cold climates. Last frost date is just not practical - many early varieties will have bloomed long before then. The chief benefit of the burlap or other protection is to shield the rhododendrons from winter sun and wind - they do not modify temperature except possibly in a very minor way, so hardiness of a particular rhododendron variety is not really a factor in when protection can be removed.

If you've had a mild winter and there is little frost in the ground, it's probably fine to remove the burlap within the next two weeks or so. Checking the long range forecast for possible cold snaps is a good idea. Wind can also do some damage after the burlap is removed, so checking for the possibility of strong winds is also important.

It would be nice if there were a hard and fast rule, but there is none. I erred last year when I took down screens the 3rd week in March. Right after, we had a two day period of strong drying winds. Many rhododendrons looked terrible for a while, but all recovered in time.

I planted my very 1st Azalea (Poukhan-Korean) a whim purchase no less, in Spring 2010. With no knowlwdge of Rhodis/Azaleas to start w/ & learned just a bit from reading in forum, after just following loyally, the planting/care/maint on the tag.

Nowhere have I read on overwintering or I wouldn't have given in on the urge, then (I have too many Hydrangea Divas as it were). I've never given this little beauty more than conventional atten. much less, a winter coat, altho she has Pachysandra around, protecting her feet w/ mama Duchess Ginkgo above her she grew unattended gracing the site w/ her breath-taking blossoms (sigh .. poor girl!) But then I see tons of Rhodis/Azaleas around the area seemingly happy w/o covers in Winter.

? ~ feeling bad now, just patches of our snow left & ugh .. Winter clean up ahead .. revealed! Will it still make a diff to make it up to this *Cinderella* for her to grow into the real beauty she could have been these past few?

Doing my "Mea Culpa" & TIA

Thanks for the tips! Some brutal weather arrived and now I am relieved I did not do anything rash. Somehow the area I am in is a bit tough on rhody's even though we are near Lake Ontario which you would think would be a milder climate, but it is actually quite unpredictable. They are not commonly grown here. I don't have a really sheltered spot either - just one tall evergreen nearby but pretty high branches and some deciduous. but a friend gave them to us and I do love them so I try my best. They are all 3 blooming pretty well for the past couple of years so I'm hoping for another successful year if I coddle them some more.

You said they were currently small. If they do not get large, you could try growing them in pots of you are into that kind of thing. In pots, you could move them back inside if "brutal weather" is forecasted. Of course, you then have to move the heavy pots into and out of protected areas twice a year and be careful of watering and fertilizing more.... Hee hee hee!

Since you & they have been into the over-wintering ritual these past years perhaps should continue until they are really grown & taken a good hold of your zone & clime.

Looking thru my binocs, my nearly 4y/o, Cinderella has grown but all her leaves are curled (seemingly cold out there) tho AM sun surely warms her! Spring should be here soon & I'll see how she really faired yet another year!!!

About toughening after some maturing ~ I have a pair of hydrangeas I gave winter cover-ups in their youth are now grown & on their own! Some harden & acclimate after a few years.

Luis' idea of potting is another thought, over-wintered away from "brutal" winter events. I have a few in containers (not Rhodis/Azaleas) hardies, but fear freezing their toes ~ I over-winter them in an old grandkid's play-pen, lined around & top-covered w/ landscaping fab til Spring & still others I park in the garage just watered once or twice.