There is a big learning curve to GHs.

1. How low the normal or lowest temperature can it be over winter? What is the lowest temperatures your plants can survive at? Do you want them to just survive or be healthy?

2. Any other protection I'll need to protect the tender plants inside? You mean besides the Greenhouse itself? Ya, heat, from some source or another. They don't heat themselves...I am NOT being a smart aleck here.

3. If the winter temp is too low, would it make sense to install solar panel/battery and to heat it overnight? However you want ot heat it, it will need some type of heat source to keep tender plants (of which we do not know) in zone 6b from dying.

Also rememeber the smaller the GH, the harder it is to regulate temps. It may get too warm during the day, and freeze at night with out some type of regulation. Best advice is to search the internet and do some reading up on greenhouses before you buy one. Your learning curve is just too steep right now.

Q1: I do not intend to grown greenhouse plants, but just to winter the plants and keep them alive.

Q2: I meant any additional cover. The plants will need some light to survive.

Q3: Cost is the main consideration. The main goal is to keep the plant alive over the winter with minimal cost.

1. What plants? and what is the lowest temp they can take and survive? That is what you want to keep it at. You have to answer this for yourself...

2. Solar covers work well from what I hear. Do a search on them on this forum, there is plenty already written.

Zone 6b nighttime average temperature is 0 to -5 F. Most plants will be frozen rock hard at that temperature. In an unheated greenhouse, it probably isn't a good idea to keep plants you want to save in your zone. Greenhouses that are used to keep plants alive in winter can't fall below 32 F. (probably a minimum of 40 F. conservatively) because the plant cell structures will be damaged.

Here is a link that might be useful: Zone chart for NJ

It depends on the plant. Some plants can't go below 50*. depends on the plant what the lowest temp can be. they need to find the plant that is the least hardy and set their temp goals to fit that plant. The other half of the equation is which plants MUST go into dormacy and if it is a sustained cold, are the other plants that may not need a dormancy going to survive the cold.

The plants I have and intend to protect for winter include:

Jasmine Sambac, star jasmine and Jasmine "Grand Duke"
Kumpkua (sp?) orange

The jasmines won't take anything below freeze, so I'd say it has to be above 35 degree. The orange is more hardy.

I do not intend to get more tender plants. If the plants can not stay in the greenhouse w/o heating, then I'll just keep them in house....

Achang, I've just put up a small glazed structure. Since I'm also in NJ (along the shore), Zone 7, I'd be happy to share results with you if you're interested. If I read your post right, I think we're on similar tracks: wanting to extend the growing season and care for some marginals, though I haven't yet ruled out adding some heat to overwinter a few more tender plants.

One consideration I've been thinking about recently: There's a difference between wading through fallen leaves in 40 degrees and traversing snow and ice in 20 degrees to get out to the plants.

Little off subject here:
"There's a difference between wading through fallen leaves in 40 degrees and traversing snow and ice in 20 degrees to get out to the plants."

So make sure your path the g/h is not dirt you the wife/husband is going to get very annoyed of the mud you bring in.

1: Intellicast.com can give you the average temps in your area.
2: Your plants will not survive outside in winter without supplemental heat. I'm in 6a and your houses will freeze with out heat. It will be just as cold inside as outside.
3: What ever heat source you chose, make it as dependable as possible and buy some type of temp alarm. Something always breaks in winter and it's usually at 2:00am.

It seems the best way for my situation is to baby-sit the tender ones inside the house and use the unheated GH for propagation and seed starting. I do not have plan to build a modern GH with water and electricity and try to keep it functioning over the winter.

The other option is to build a attached GH and use the house heat to keep the GH alive. But this probly won't help much....

Achang,

I'm not familiar with that variety of orange...maybe it is a kumquat?

Your citrus may be better off inside the house. Absolute zero for citrus roots is 55F and below this they will not take up water or nutrients. In the light, they will continue to try to photosynthesize, and when this fails at low temps, leaf drop (or worse) will occur.

Be careful when you bring the plant indoors. Frequently, people wait until it is cold outside, then they bring the plant inside and place it in a sunny window. As above, the leaves will try to photosynthesize, and if the container and growing medium has not warmed enough, you'll get the infamous "winter leaf drop."

Avoid this by bringing the container inside when it is still warm outside. If that is not possible, let the soil warm up before placing the container in the sunny window.

Hope this information is helpful. SB

Ah, achang, an attached structure is exactly what I'm dreaming of! Not ready to make that investiment just yet, though I understand we can get a tax credit for a "solar improvement."

By all means, be realistic, but don't forget to follow your dreams to some extent. If I'd listened to the local "experts", I wouldn't even have grass in my yard, let alone bulbs, perennials, vegetables, ... and even, oh my goodness, ROSES! When we moved in not even WEEDS grew here! (I even decided to wait a full year before disturbing the soil to see if the prior owner had planted anything.)Books and rules are great, but my #1 rule is: Don't let the plants read the books! Who was it who said "If you don't have any dead plants, you're not trying hard enough"? Please don't misunderstand, many of my plants are dear to me, having come from former family homes or from friends, but I do believe in pushing the boundaries just a little ... that's what makes things interesting.

Best of luck to you, whatever you decide, and, most important of all ... enjoy!

Diane

Pushing the boundaries is one thing, but throwing your plants off a cliff is another.

Yep, that's about what the nurserymen around here were telling me ... advised me to stick to begonias, impatiens and hostas.

What?! That's ridiculous, you're not that cold. You have the choice of tons of plants and a fabulous garden. No big deal where you are. Send those unimaginative nurserymen to zone 3 where they belong.

I am all for starting seeds and growing them on to transplant size in a minimally heated structure in the spring. If you have minimal or no supplimental heating the biggest problem is it is TOO hot in there during the DAY.

I say that because the temptation is to run the greenhouse as hot as you can during the day so as to store up enough energy in there to make it through the sub freezing night. This causes me to have major problems with "leggy" plants, too hot but not the corresponding intensity of light

However, starting seeds in spring against all odds means things will get better! The weather WILL get warmer, the work you have to do covering flats at night, and sometimes moving everything indoors into the basement for days when the weather gets really nasty, will reduce. The worst part is at the beginning, it then gets better.

Now as to putting anything in a minimally heated structure in fall... It is easy to start with, then as the winter deepens it gets harder and harder. The knowing when to quit moving stuff or install a big heater is difficult to decide.

I have overwintered perennials in pots with very little success. I don't try it any more. The big problem? They break dormancy when you have several days of warm (relativly) weather and above average warm nights. Then what do you do with them?

If you deleted the "warehousing several tender plants" from your first question then I would say "Go for it!!"

It wasn't the cold, it was the sand/clay soil devoid of any nutrients and the high dappled shade under tall oak trees. Seriously, we didn't have any bugs, worms or weeds.* I amended the beds like crazy, started ordering from catalogs (no internet back then) and took some chances on some perennials. Amazing how well most performed in a combination of full sun/dappled shade. With that I'll try to bring us back on topic ... how much risk are you willing to take for a few surpises. I certainly wouldn't count on it, but have had snapdragons overwinter out in the garden, unprotected save for a pile of late-fallen oak leaves; these were not new seedlings, the new growth in spring was from the old brown stubs that had been there all winter.

*BTW, we now have worms, bugs and weeds ... and a greater number and variety of birds :-) As for the nurserymen, most have broadened their views & selection over the years ... those who haven't, I'd love to send up to a zone 3!

StressBaby... I'm not so sure about tha causes of citrus leaf drop. I have 5 or 6 citrus, a couple of mandarin oranges, a couple of grapefruit and a couple of I-forget-what-i-planteds. The oranges tended to get infested with spidermites over the winter so a few years ago a decided to toss them in the garage for the winter as i just didn't want the mites spreading to other plants.

My garage walls are insulated and i do have insulated doors, but there is no addotional heat. All heat is from the windows (I have 3 large south facing windows), what must leak out from the house (insulated 2x6 contruction) and whatever heat comes from the engines. I am in zone 5, massachusetts. I do occasionally get ice on the floor if the outside temps stay below zero for a few days.

That first year, i did get the leaf drop you describe. I really thought i had lost them all. One lost about 90% of it's branches, the rest lost most of their leaves. But come Spring, they cam back to life and recovered fully.

The following year, i decided to take better care of them since they deserved a bit of credit. I made sure i stuck to a weekly watering plan and that was enough to prevent almost ANY leaf drop. I did get a bit of freeze damage on one tree closet to the doors. This was closer to the springtime when they had started sending out new growth.

SO i have now overwintered the in the unheated garage for 3 winters. Temps have been as low as -19F at night outside, and i hardly get the leaf drop. I am of the mind that it was completely due to my neglect that first winter and the lack of water.

This winter i plan to put a themometer in the garage so i have an idea of what the temps actually are, but i am pretty much amazed they do so well.

Poppa

WTG, Poppa!

Poppa, that's very interesting! I'll be interested in hearing what temps you have in the garage this winter. Given the fact that the citrus survived, I suspect you'll be over 28F much of the time.

WLD, the way I understand it (and I'm no citrus expert), is due to supply (roots) not keeping up with demand (leaves). This has less to do with the absolute temperature as it does with the temperature differential between roots and leaves. So when you bring a pot in from outside, put it in a 70F sunny room, you have 80F leaves when you might still have 45F soil temp. I suspect part of the reason you have no WLD was that the metabolic demands at the top of the plant slowed enough d/t cool temps and lower light that the roots could keep up.

Let us know what temps you have this winter, I'm very interested. SB

Chris
"This causes me to have major problems with "leggy" plants, too hot but not the corresponding intensity of light"
This is also true due to the extreme fluctuations in night temp to day temp.
You are very correct that the heat in the day will stretch the plant nodes.
An unheated cold frame (which is what the thread was originally talking about) still needs vents and exhaust and HAF fans. Frost only forms on nights with no wind. HAF's will eliminate this.

"I have overwintered perennials in pots with very little success."

Setting the thermostats to 35 degrees will help eliminate this heat during the day and the premature growth you saw.

A cold frame without the vents, exhaust and HAF's will not work and most likely will result in plant death.

COuldn't put them in a basement with some overhead lighting???? Be a lot cheaper to heat!