Overwintering in containers--yea or nay?

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ccayton
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Overwintering in containers--yea or nay?

Post by ccayton »

Chris W.--
With fall and winter around the corner, I am planning out my steps for winter storage of all my potted perennials!

Over the past few years, I have had great success with placing my containers with hostas, daylilies, ferns, clematis, etc. in the garage to overwinter. I will do so again this year! (I've read these plants require the cold season/dormancy, so the garage merely protects the roots from the extreme temps.)

However, my puzzlement is over some new plants I acquired that I still have in containers. (I don't know if/when I will plant them in the yard, so I need to protect them until next year.)

Question 1:
Should I overwinter the following perennials in the house, where the temp is around 65 degrees and they get some sunlight, or should I just put them in the garage that can get down to 35 degrees and has very little sunlight?

--Azaleas
--Rhododendrons
--Boxwood
--Pieris japonica Mountain Fire

Question 2:
What does the greenhouse do to overwinter the perennials that need to have a dormancy period? Constantly open the roof to keep the heat out? (I assume sunlight/darkness is not a necessary factor for semi-evergreen plants?)

Question 3:
If I kept a few heuchera/ella in the house, how damaged would their health actually be?

Thanks! Who better to ask than a beloved greenhouse expert! :wink:
Carrie
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Re: Overwintering in containers--yea or nay?

Post by Chris_W »

Dear Carrie,

Personally we grow 90% of our plants in the ground and try to get most of the potted plants back into the ground before winter. The exceptions are our heuchera, which most of those we actually grow year round in containers. We simply tip the pots on their sides, bait for mice, and then cover with a frost blanket. The blanket allows some moisture penetration but keeps most of it out as too much moisture is the bigger cause for rot.

When we used to overwinter in hoop houses/cold frames, we cover them with overwinter film (white) but keep the ends of the cold frames completely open. This allows excellent air circulation to keep things cold but again, it keeps the moisture out. Most hardy shrubs would do fine in this condition too, but without a greenhouse like this then the unheated garage is your next best thing.

We seem to have better results overwintering woody plants in containers just pushed up together and left in the shade out of any direct sunlight. Last winter we overwintered several types of hydrangea paniculata, boxwood, and arborvitae in pots without any trouble. Personally I do terrible with Rhododendron, but these need excellent drainage and protection from the winter wind to keep the foliage from completely drying out. That might be the toughest to overwinter.

I hope that helps a little, but obviously there is no guarantee that you will have total sucess with pots. Often it has more to do with having a really well drained potting soil that isn't soaking wet than cold that helps with success.

Chris
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ccayton
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Joined: May 29, 2008 9:21 am
USDA Zone: 5b
Location: NW OHIO, USA

Re: Overwintering in containers--yea or nay?

Post by ccayton »

Thanks!! That was a wonderful response! I appreciate all the info! :D I may try some inside the garage, and some outside with protection. Either way, I'll try to make sure they have good drainage!
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