Overwintering plants

[kreyn13]

Hello.
A local nursery is going out of business and had greatly discounted plants, so I bought several. These include hydrangea, Rose of Sharon, lilac. Geraniums, gardenia and a few others.
I have never been successful at overwintering plants, as I'm really not sure how to go about it.
I'm in northeast Ohio where the temperatures have been around freezing and I exprect them to continue dropping. Would the best options be to attempt to plant in the ground and then cover, overwinter in the detached, unhealed garage, or buy some sort of cold frame?

All information is greatly appreciated!

 

[Oliver Buckle]

The main killer is pots freezing through, the roots can't take it when the plant often can. Pots stood on the North side of the greenhouse with leaves accumulated between them seem to survive well.
I have never understood why the North side, I would expect it to be the coldest, but I read it years ago and it seems to work.

 

[Meadowlark]

You need to do some homework and come up with a plan for each specific plant variety.

This is what I would do:

First, I'd determine your low temp for your growing zone...the expected low temp for the winter (let's call that ELT for short).

Next, carefully research the low temp tolerance for each of the plants (specific variety not family) you have, i.e. the temp below which the plant typically dies. (for short let's call that LTT)

For example (and again it depends on the specific variety as some plants have special cold weather varieties):

Hydrangea...20 deg F
Rose of Sharon.... -20 deg F
lilac... -60 deg F
Geraniums...10 deg F
Gardenias...15 deg. F.

Where the expected low temp is below the low temp tolerance for a plant, some kind of external heat is required or expect it to die.

Expressed in simple math, when ELT < LTT for a given plant, some kind of external heat is required.

Unheated garage is an option only if the plant can get adequate sunlight or artificially provided grow light and the ELT is never below the LTT.

Cold frames will have to be heated when ELT < LTT... and so on.

Depending on how many plants you are talking about, you may be looking at a daunting and very expensive undertaking.

 

[nvidura]

That’s awesome you got those plants!
For overwintering, you can try planting them in the ground and covering them with mulch or burlap. If it’s really cold, a cold frame or your garage could work too. Just make sure they’re not too warm in the garage, or they might start growing early.
Keeping them cool and protected from frost should help!

 

[kreyn13]

Thank you! I think I will try to plant some with mulch or burlap as you suggested!

 

[kreyn13]

You need to do some homework and come up with a plan for each specific plant variety.

This is what I would do:

First, I'd determine your low temp for your growing zone...the expected low temp for the winter (let's call that ELT for short).

Next, carefully research the low temp tolerance for each of the plants (specific variety not family) you have, i.e. the temp below which the plant typically dies. (for short let's call that LTT)

For example (and again it depends on the specific variety as some plants have special cold weather varieties):

Hydrangea...20 deg F
Rose of Sharon.... -20 deg F
lilac... -60 deg F
Geraniums...10 deg F
Gardenias...15 deg. F.

Where the expected low temp is below the low temp tolerance for a plant, some kind of external heat is required or expect it to die.

Expressed in simple math, when ELT < LTT for a given plant, some kind of external heat is required.

Unheated garage is an option only if the plant can get adequate sunlight or artificially provided grow light and the ELT is never below the LTT.

Cold frames will have to be heated when ELT < LTT... and so on.

Depending on how many plants you are talking about, you may be looking at a daunting and very expensive undertaking.

Oh, good point. I hadn't thought about them having different temperature tolerances!

 

[kreyn13]

The main killer is pots freezing through, the roots can't take it when the plant often can. Pots stood on the North side of the greenhouse with leaves accumulated between them seem to survive well.
I have never understood why the North side, I would expect it to be the coldest, but I read it years ago and it seems to work.

Interesting, I would have thought it would be the coldest as well!

 

[Oliver Buckle]

I'm not sure I would want to plant them out this time of year, they are not going to start adapting to their new condition until Spring, maybe best leave them undisturbed 'til then?
The advantage of being in the ground is protection from frost for the roots, it is rarely that it is below freezing very far below ground level, bar permafrost If the plant is hardy the part above ground can take it, it's the roots that are vulnerable. If they are deciduous they won't be needing lots of light and you can stand the pots close together so they act as a block and hold a bit of heat, you can get things between the pots as well, but you don't want it to get wet and promote fungal problems. Another possibility is digging out a trench and burying your pots, or even burying the pots where yo envision being their final position, that would give you the chance to consider it before you dug them up, released them from their pots, and put them in their final positions.