Better hardening/cold resistance is something that is typically governed by the plant's DNA, not timing of a weather event and the opening of leaf buds. I am not sure I followed the scenario but leaf buds that open in a cold (I assume sub-freezing) spell may be injured. If it is quick fall & warm up... not terribly below 32F then there may not be damage. There are three flavors after the drop below freezing: the leaves are not injured, the leaves are partially injured (a little) or the leaves are zapped for good.

A drastic change in environment - from the cold frame outdoors into the house - is going to result in some sort of stress to the plant. It is pretty much inevitable. I'm not sure one can draw any conclusions about hardiness or cold tolerance from that. The two issues are not really related.

Yeah, I know the OP was confusing. Let me try to re-word it. For Hydra planted outdoors, those with buds that have emerged (green) or new growth from base (green), they are still green and are fine even in this cold weather. Hell, even the Noreaster with snow did not seem to faze the new growth at base level.

The Hydra I grabbed from cold frame last week - lotsa leaves if not small, but set blossom on each end (counted at least 10 flower blossoms) - was removed from cold frame and placed indoors on a bay window. The ambient indoor temp is 70-72F. It's warm when there is sun during the day, but when either overcast or just@night, the ambient temp by the window is much colder - can't say how much, but it's definately colder by the windows.

Maybe it's just environmental/thermal stress, but a majority of the leaves have gone from upright and ridgid, to soft and wilted. So the ? is are they leaves wilting due to not experiencing cold like we speak.

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GG

We were typing at the same type. Hopefully these leaves unsoften themselves and perk back up. Or less continuation of leaves wilting...

Terrible analog but this time of the year, where there are potted gift Macros everywhere. Is there some sort of ~agricultural juice~ that these Hydra's are given@ the greenhouse that gives these leaves the stamina for the selling period ?

I just realized I bought 2 for ~cemetary visit~ and actually put these gift type macro's outside and just kept them inside a cardboard box. They sat in the box outdoors for 6 days. This Sunday, the leaves were still stiff, ridgid and upright

Surely, the temps at Home Depot/Lowes is colder during the day and @ night than my Bay Window.

Wilting after a cold spell may suggest that there was some injury to the leaves from the noreaster. After a sub-freezing cold spell, I have seen them (after wilting) turn an even darker shade of green before turning brown and falling. But it all depends. Maintain the soil moist in case a burst of water is all they need. If they do not respond to some moisture then I would assume they got zapped. Then see if they are able to still perk up or not.

I have not heard of "a juice" or "a tea" used in greenhouses but those fancy greenhouses can control temperature, moisture, food, light very well. So if you control all that, you can confuse the shrubs into growing and blooming at times that normally would be considered too early. Would something they did make them winter resistant... ???... No.. Just saying...

If the soil was moist when the bad weather hit, who knows if that helped; if there is a micro-climate that helped; etc. I would not try to compare the two sets of hydrangeas since the locations are way too different.

These greenhouses do have special juice . I know they have retarders that can slow the growth down, so they can time the perfect bloom time for easter, mothers day, etc flower sales. Or flat packs that have blooms just in time for memorial day spring sale, etc

Well, I decided to just put the shrub outside. It's will recover and grow back new leaves if it wilts. It will recover by getting the power of the sun I suppose. Hoping it doesn't setback and recover and just straight up recovers. Final shrub that needs tending to.

I was tempted to put them under my new LED grow lights. But who puts a outdoor plant under indoor grow lights ;-) Only a fanatic. Supposedly these new LEDS are the schnizzle nizzle. Has blue, white, red, purple spectrum. IR, UV.

Off to deal with other matters at hand....now that's technically spring. Seems like a yearly thing now. Ants scavenging for food and water. I've some some sugar ants in the house that I need to lay down some bait to get rid of the mother. Uggh.

Gee, what a way to "start" Spring?!?!

I have to do some more research or reading. It's not like something drastic has changed@home and maybe it's the earth/mother nature I swear. Literally, never a problem until like 3 year ago. 1st year, they were in the Living Room. Last Year, Ground floor bathroom and Kitchen. This Year Dining Room and Master Bedroom Bathroom .

Previous years, nary to nil on sugar ants. But it seems like clockwork or coincidence, they have been coming in for the last 3 years in a row. Head Scratcher but more a PITA doing ant mitigation..

The wilting has stopped. I guess I was babying it too much by keeping it indoor. Or it just likes the suns UV during the day. I did lose a couple of nice leaves with a budded bloom on it ! Heh, I just need to find some space for a cold frame of my own.

Off topic, but the 10G Bloomstruck I over-wintered in a fabric pot - yes, fabric pot - I can say is cold hardy. I don't know how much of the core of the pot was frozen but the exterior top surface and sides were rock hard in winter. For sure I thought I had killed it by overwintering it in a fabric pot no less. Anyhow, it's budding out all over while most of my older Mac's are still dormant. I was kinda surprised and relieved.

In cold areas where the soil freezes, hydrangeas planted in the ground "suffer" from the conditions that the pot had. It is normal (in cold areas) does not affect the roots much. Good to know they started budding out. Do provide mulch to help a little in Winter (and in Spring, Summer and Fall).