You can probably get a zillion of "appropriate" times to plant hydrangeas here. Mine: because I do not like to mess around with the leaves getting zapped by late frosts and such in winter, I wait about 2 weeks after my avge date of last frost.

Hydrangeas do not do well indoors so, you may have to plant the lacecap outside and see how it does or grow it in pots and bring the pot into an enclosed garage during winter.

Most "named" mopheads and lacecaps do well in Zone 6 or higher. In Zone 5, you sometimes have to winter protect. Note: should these hydrangeas rebloom, you could leave them outside unprotected and still get bloomage, albeit later than you would if you had winter protected them.

Unnamed mophead/lacecap hydrangeas are the ones you buy at grocery stores or florists. The label/stickers read "Hydrangea".... or maybe "Red Hydrangea".That is it. You are left wondering if it will do fine where you live during the winter months.

Some of those unnamed hydrangeas have a hard time with winters so some people throw them away after blooming has completed. But some unnamed hydrangeas, however, could actually be named varieties that can handle winter (or that can handle them if you winter protect) so, I say give them a try outside anyways..
Talking about names.... do you know the names of these varieties? If so, post the names since someone might recognize them and tell you more about them.

For Zone 5, the hydrangeas I would search for are reblooming Hydrangeas macrophylla; Hydrangeas arborescens; Hydrangeas paniculata; and Hydrangeas quercifolia (aka, oakleaf hydrangeas).

I hope you like your new plants!
Luis

This post was edited by luis_pr on Fri, Mar 14, 14 at 7:21

Nearly all lacecap and mophead forms are the same species - bigleaf or Hydrangea macrophylla - and should be equally hardy. The exception is the serratas or mountain hydrangeas (also lacecaps) and those are considered even a bit more cold hardy than the macs. These all should be root hardy to at least zone 5 (they often quote zone 4 for the ES series, bred specifically for extra cold hardiness). But they will all still require winter protection to reliably preserve and maximize flowering potential in your zone.

Greenhouse grown hydrangeas have a much reduced chance of succeeding outdoors long-term in colder zones, why I am not entirely sure. I would guess the coddling and manipulation with ferts and growth hormones they receive in the greenhouse environment somewhat impacts their genetic hardiness. If you are going to try it, wait until at least May and then gradually acclimate the plant(s) to outdoor conditions. Plant in an area that receives part or afternoon shade in a rich, well draining soil. Keep evenly moist. And then protect very thoroughly for at least the first winter and until all chances of late freezes - not just frosts - is well past.

Otherwise the hydrangeas Luis suggests above in his last paragraph should do well for you with no or just minimal winter protection.