I'd leave them outside and only provide protection, like a unheated garage, if the temps plummet. Inside you cannot possibly encourage them to go dormant :-) Dormancy is triggered by shortened daylength and cold temperatures, which are seldom found indoors. As to requiring dormancy, most plants from temperate climates do require some period of cold temps and dormancy. However, my sister in zone 10 SoCal has numerous hydrangeas in her garden that never seem to experience a full dormant period like mine do and yet they flourish and bloom well.

btw, woody plants when dormant do not require sunlight. That is far more of an issue when in leaf, as sunlight is required for photosynthesis. When dormant and out of leaf, the plant is in a condition similar to suspended animation - no photosynthesis and very little root activity going on.

thanks gardengal. I've moved them back outside. When you say plummet - what temperature are you speaking of? The low for tonight is supposed to be 30 degrees. Tomorrow 31 degrees for the low and then back up in the 40's. Should I put them in the garage?

please forgive all the questions, this is my first winter with hydrangeas.

Thanks again!

Right around freezing is fine.......anywhere in the lower 30's. If it should get down into the 20's for any length of time, I'd be concerned then. And if you have a covered porch or something similar, I might not be concerned even then :-) I grow a lot of stuff in containers - have for years - and they do just fine. Have even survived a number of days/nights in the 20's without problems. But then, I do use pretty large containers for most of my stuff and I group them all togther during winter. That creates a bit of microclimate with the transpiration.

I'm in gardengals same zone, and I don't worry in the low 30's or even upper 20's....neighborhood of 28ish if we are talking only about dipping to those numbers briefly overnight and not extended round the clock freezes for a few days - as happens rarely but did recently.

Much below 28 and I move things either up against the house, or out of freezing winds into a carport and cover temporarily with old tablecloths. I've used a large lidded plastic tote too, again - temporarily and just until the storm passes. A neighbor has had good luck just tucking pots of things she might be concerned about under her large and dense rhododendrons, even that evergreen foliage will add a few degrees of protection.

One particular winter night as an arctic blast was settling on us without much warning, I put young containerized rooted cuttings into the back of my SUV in that carport for added insulation - that was about the best I could come up with in pajamas without resorting to bringing plants into a too warm room :)

I've never been to Dallas, but I'd bet that you could just leave the plants outside for the whole winter and never have a problem. (You might put some mulch around the roots in the pots to keep the root ball from freezing, but I'd bet that's not even going to be a problem.) Upper 20's should never be a problem for you. If this were to happen after a month of 90 degree days, then you might have a problem, but not if the plants have had a chance to move into the winter pretty reasonably.

I overwinter my potted plants outside, covered up with bags of dry leaves. I don't even think about covering them up until I see that the temperatures are going down to about 20 degrees....and I'm pretty sure that I put them away too soon at that.

Keep in mind that plants do quite well at Cape Cod and New York City. Go to your weather service and check out the temperatures there when you begin to worry about yours.

Hay

Thanks everyone. I'm not sure how I missed the first two replies. Well it hasn't dropped past 20 degrees. We have been in the upper 20's here in Dallas. I've moved all the potted plants into the garage and they are finally losing the leaves and turning woody. I think they are doing good. This weekend it is supposed to rain and on Monday it's suppose to drop into the teens, so I guess I'll leave them in the garage.

Thanks again!

Just to clarify......it is not so much concern for the top growth and potential damage to latent flower buds at temps into the low 20's but rather root damage. Plants grown in containers are at risk from root damage when temperatures drop too low and stay there for more than a night or two. Without the insulating properties of all that soil mass around them, roots of containered plants are often more vulnerable to cold damage than is the top portion of the plant - and root damage can have far more serious results. For many woody plants, this damage can occur around 26-24F.

Leaving them in the garage during the coldest weather is a sound idea :-) And it won't hurt to leave them there all winter, if you prefer.

Thanks gardengal! I have them in the garage and they are all dormant. I've been watering once every week but not much. I can't wait until Spring for new blooms and to be able to move them back outside!

Thanks again!

What about watering? I brought my potted hydrangea into the unheated garage as we have temps in the teens and low 20s regularly. Do I need to give it water or should I just let it sit quietly till spring? Thanks in advance.

Hi ellen218,
absolutely water it. it's very important that the hydrangea gets water during dormacy. They still need moisture. I water about once a week and not very much just enough to get the roots wet.

Thanks, hope I haven't killed it! I guess we wait till spring and cross our fingers.

How long had it been since you watered? If it were just a week or two, it should be fine. Make sure to water weekly from now until you set it out for Spring.

You can insert a finger into the soil and water if it feels almost dry or dry. In my attached garage, it seems like I have to water around every 9-ish days. Nurseries also sell gizmos that change color when the soil is dry. You could try to see if these things works for you.

OH, I brought it in probably around the first of December and haven't watered since. I read somewhere not to water till February, so I just let it be. Now I'm watering once a week along with the ferns that I'm keeping alive in the garage. I appreciate the advice.

Hello....I have a couple of young rooted cuttings in pots placed outdoor near my gardendoor. It is still green with leaves attached....not dormant yet! And temps in my neck of the woods is as low 2-4 C (around 36-40 F). Temps in the next few nights are expected to dip below 35F. Should I leave them in the same spot until they go dormant before taking them into my shed/garage or? Last year this happened as well and by the time I rememmbered to put them into my shed it was too late....they were root dead! Please help! (I would like to keep them this year!) Thank you so kindly in advance.

This post was edited by starlight99 on Mon, Nov 10, 14 at 17:32

I don't know where you are but I'm in Coastal NJ (6B or 7A - depending on the map you look at). In the past, I've buried my cuttings almost to the rim of the plastic pot and covered them with shreadded leaves sometime in December and they did fine. But last year was very cold and my only cutting was lost. This year is expected to be another cold one. So I plan to put them in the shed once the leaves are gone and night time temps are in the 20s. I've read this is the best for potted plants but not sure if it's the best option for cuttings. Thoughts?

I am currently trying to make my big leaf hydrangea to go dormant right now. (I just received it at Christmas as a fully active specimen). It's -31C outside right now (-23.8F) and I have a bungalow-style home, forced air heat, thermostat is upstairs. So that means my basement is chillier than the upstairs. I have a very small "cold room" in the basement and it is 7.3C in there right now (45F). It has stopped growing and I am trying to do this slowly so that it goes dormant properly. I have the light on and a small fan for circulation (I noticed some powdery mildew spots on one leaf). I expect to see it continuing its dormancy but it does seem like a slow process. Because it's so darn cold outside, I have an empty spare fridge available sitting at about 1C for its winter sleep. I will wrap it well so it does not dry out and water as needed. That's my plan anyway, hope there are no holes in it. Yes, it will be more work having this type of Hydrangea here where I live, future plans are massive winter coverings and possible heat tape, lol. (I have power where I plan to plant it).

Don't feel left out regarding making them go dormant. I have another one that refuses to go dormant over here too. Temps are going slightly below freezing at night for the next few days. Maybe that will make it sleep or snore, whichever... Hee hee hee!

I do not think I have ever heard from anyone in Zone 2. Where are you? What is it like there, Jackie? Or send me Gmails so we do not "steal" the post from msalcido.

I'm in Drayton Valley, AB, Canada (central AB bit SW of Edmonton). It will be getting to be -34C tonight. This is the second cold blast we got (polar vortex?) this winter so far. Then it will be getting mild again soon. I think there is a limited choice of plants that will grow here. We are officially zone 2 Canadian hardiness. It can get much colder here. Last winter came in brutal....burning bushes got severe dieback after being here 3 years....winter came in with brutal winds and -25C right at the beginning and shocked the borderline hardy plants. However, I do have a zone 5 Royal Purple smokebush I completely cover with snow and it does well....only the third year coming up and had small dieback the first winter. I've learned to cover pretty much everything but the natives (spruce trees, pines, willows, etc). So tempting to try borderline hardy plants here due to lack of choice. Sorry for hijacking thread. :) And thank you gardengal for the info. Can't blame me for trying, lol. However, I do have the Explorer roses (John Davis) and they survived last winter beautifully, even with that cold shock first thing. Truly zone 2 roses, and they bloomed crazy all summer. And am trying hydrangeas too. Annabelle grows fine, and getting Pee Gee this year. Should be fine from what I heard. But SOOOO tempted by the big leafs......

Just checked....cold room is now 6.7C (44F). Will get colder tonight. Might be able to store a big leaf in this room for the winter if I didn't have a florist type. lol

I doubt it. At 14F, even a regular bigleaf hydrangea in a container would need winter protection. You need a cool area that stays between 30F (not much lower) and 40-45F. Plants in containers are far more susceptible to root damage from cold temps than those planted in the ground and 14F is too cold for most.

Hi Jackie Bostonz6 ,received a Easter gift Mathilda Gutges 15yrs+ ...in ground no Winter pro, blooms every yr....also Blue Billows ( 20yrs) every yr.....i

I know Big difference between, Z2 &6...Just saying

Sorry, I typed in 14F in at first instead of 44F. Edited now. Thanks so much gardengal. ;)

Not a "big" difference........a HUGE difference!! Average minimum winter temp for zone 6 is 0 to -10F. Average minimum winter temp for zone 2 is -40 to -50F!!!!

Not sure why one would even bother to make such a comparison. It will just not be possible to grow any Hydrangea macrophylla in the ground in zone 2 regardless of how well it is winter protected. The ground will freeze solid to many feet in a zone 2 whereas it will freeze only a few inches and then for only a relatively short time in zone 6.

ETA: 44F is just about right for your cool overwintering area. Maybe slightly on the warm side but not too bad. Would prefer if that could come down closer to 35-40F.

Um, ya gardengal. Few years ago we had a -45C (-50F) Christmas right here. In fact, I heard it's -39C (-40F) in Whitecourt right now (town a couple of hours away). I thought it was ok for the soil to freeze solid, lol.