Need suggestions for Zone 8b plants

I'm in lower New York State and it cost me too much last winter to heat the greenhouse attached to the front of my house. I'm thinking of not heating it next winer. The difference in temperature is usually about 20 degrees. Therefore, if I put Zone 8b plants in there they would fare at l5 degrees below freezing which would be -5 degrees outside. If it got any worse than -5 I could put an electric heater out there for the night. Does this make sense? Finally, what zone 8b container plants would you recommend for this situation?

Any help will be much appreciated.
Thanks, Berengaria

I'm not sure that keeping the GH at 15 is going to be good enough...most plants rated for zone 8b could handle a short exposure to temps in that range, but if they see those temps night after night for much of the winter they're not likely to be happy. You need to look at what temperature typical nights in zone 8b would be and try and keep the plants in that range...my guess is in real zone 8b you have a lot of nights in the 30's, some in the mid to high 20's, and very occasional cold snaps where you'll get to the high teens or low 20's for a night or two. If you can mimic those conditions then your plants will probably do OK, but if you end up with too high a frequency of nights on the colder end you may start to lose some things.

Thanks ecrane 3 for your heads up message. I understand what you are saying and will give it some more thought. This last winter was exceptionally cold and we had many nights in the single digits but none that I remember below zero. Allowing for 20 degree difference, that would be many nights in the 20's inside the greenhouse. Since 8b went to l5 degrees I thought that would clear it but perhaps you are right and I should move it up a notch to zone 7. What do you think?

Berengaria

I live in zone 8B just on the cusp of 9A. In fact some sources say we ARE 9A but I don;t believe them.
The important thing about zones here is, yes, many of the things I have are rated for zone 8. BUT that doesn't mean that they stay up, lovely and evergreen all through the winter, which here is short and usually mercifully mild. It means that they go dormant or freeze to the ground, then come back in March (now) and grow until next winter when they do the same thing.
But the real difference is, we do not have temps below 40 for many nights. They are sporadic and connected to cold fronts that blow through. So it will be 50 one night, 40 the next, maybe drop to 28-32, then warm back up.
Worst case scenario here is a string of nights below 32, which happened this winter when we had a few fronts that hung on for 2-3 days and we had 25-29F for 2-3 consecutive nights.

I can honestly say that I have lived here since 1992 and have never seen the teens. They do occur in outlying areas of this county, but not in town and not at my house. My lowest temp here has been 20F and that was for an occasional one night.

The plants I have would NOT stand 15 degrees night after night after night. If that happened, the ground would freeze here, and it NEVER freezes here. That's why I can grow a lot o f 'tropical' plants as die back perennials.

Thanks for your input gothqueen. Things aren't as simple as I thought they would be.
What plants were you referring to that are considered 'tropical' and can be die back perennials?

Some gingers, especially hedychium, hardier costus, selected Alpinias, and gingers that have a natural winter deciduous phase(Kaempheria, Globba, Curcuma, Zingiber)

Most bananas, lots besides Basjoo, but I wouldn;t try my Ae Ae outdoors, LOL

Hardier heiconias...schiediana and Rostrata always come back but never bloom outside; latispathas sometimes bloom

Calatheas, bat plants, alocasias, colocasias, xanthosomas.

Selloum philodendron, but not other more tender philos

Many bromeliads

Phaius orchids

Many passiflora

Bauhinia

Erythina cristi-gallii

Tropical water lilies

I know there's more but I can't think of them all

Go check out the Dupont Co-Op in the co-op forum. The shrimp plants do beautifully in 8b/9a.

I live in 8b here in East Texas. We do not see temps in the teens but once in a blue moon. Most of the time the temps go up and down. Cold one day, warmer the next. We got down into the 20's a couple of times this winter, but only for a day or two at a time. Most of the time it's the 30's. Plants in the ground will go dormant or die back and return when we warm up. The problem with GH plants is that they are in pots. Their soil can freeze much more easily exposed to prolonged freezing temps, thus the roots freeze. Our soil doesn't freeze so the roots are protected. If you want to grow 8b plants in the GH you will have to heat it. I have a GH and I heated it when the temps were in the 20's and 30's with propane. It's cheaper than electric and does a great job.

Good luck with what ever you do.

I use propane as well. My greenhouse is large, over 1700 sq ft, so it is expensive to heat. But here are a few tips to help you make the most of the heat you use...

Moist humid air stays warmer than dry air. If you have irrigation in the greenhouse, set it to water at night, so that the air is moister when its coldest and the heater will be more efficient. It you don;t have irrigation, you might still rig a mist system.

If you can;t do either of those, install some water. It doesn;t have to be a huge beautiful pond, although I have 2 ponds and a 20 ft stream. The water helps humidify the air as it evaporates.

Install fans that can run 24/7 in the 'attic' to blow heat does and circulate it. Lots of heat get's "lost" in the upper reaches of a GH and not utilized.

Use a heater with a thermostat that goes on and off.

I only use the heater to keep it at 50F on most nights, because I have some palms that cannot take below 45F. When its going to be 20F-29F I set it to 45F. It is expensive to heat my greenhouse because of the size, but a smaller one should be much more cost effective

Thank you Gothqueen for all the suggestions. Obviously you are an expert. I was lucky to find you. I never heard of most of the plants (I'm obviously a beginner) so it will keep me busy for a few years researching them. I hope you don't mind me getting back to you if I get stuck with something.

Thanks again.

Berengaria

Berengaria,
I don't grow any of the plants I listed above in my greenhouse. It is reserved specifically for plants that absolutely cannot survive outside a zone 10B-11 climate. But you can grow those I listed in your yard and dig them up and greenhouse them in winter. That works really well for many people. They will plant things like Plumeria in their pots in the yard, have them all warm season, then pull them up and greenhouse them. Its a good trick, if you are up to that sort of work

We bought a small wood burning stove for our greenhouse to help lower our propane costs. It really does help keep it warm on cold nights. It's a bit of an effort to get up every 2 hrs or so to feed it, but it's almost turned into a contest- see how little propane we can use.
We've hardly burned any propane, and we had some temps down in the teens, which made it hard to keep the temp up in the greenhouse. If it is 32 or above, it's quite easy to keep it in the mid 50s.
Our greenhouse is 21x26 with 8ft side walls. I don't know how big your gh is, but sounds like a stove could heat it pretty easily. The wall of the house might even absorb some heat and release it to keep it warmer longer.
The stove was reasonable, about $100, but the piping out the top of the greenhouse added on quite a bit of cost.

Wow are you certain that's a good idea? WHat happens to all the smoke and gases released from the wood burning? Seems like those would need to be vented somehow?? Is that what the piping out the top is for?

Oh my gosh yes, there is a regular chimney. Pipe, a fitting through the roof, stainless steel pipe outside, a cap... That's what really added to the cost. My husband about had a bird. But we're both happy now, we filled the propane at the start of the winter and it is still over 75% full, it's only lost about 10%. Last year we paid over $2000 and had it filled 3-4 times.

I was worried about the gases and stuff too, from leaks and opening the stove to put in wood. But all the plants are doing well- even bananas, citrus fruit, tropicals, bulbs. Even a rubber tree that is only a few feet away from the stove that I thought might get too hot is fine.

I'll take a photo tomorrow.

Berengaria, I do a lot of container plants, so I fill up two greenhouses in the winter months because I love tropicals. I have plants like tropical hibiscus, orchids, ferns of course, bird of paradise, heliconias, pllumerias, various succulents, bromeliads, poinsettias, brugmansias (which I could put in the ground here and do have some in the ground), crotons (love the colorful leaves), chalice vine, blue sky vine, anthuriums, begonias, and so many, many more.

Years ago I used a wood heater in my first little greenhouse. We even put some large rocks on the heater to release extra heat as the fire died out. Now I use propane with a thermostat controlled heater in one gh and a regular small heater in the other (next year hope to have a thermostat one in it too, much easier). I don't keep the gh hot, but on nights it's below freezing, if feels really nice and warm in there. I think you would definitely have to keep it around 40-50 degrees in there just to keep stuff alive.

Oops, forgot to take a photo. Gothqueen put the hex on me, the very next night my husband came in and said "the greenhouse is full of smoke". I thought he was exaggerating so I didn't go out there right away- when I did, I almost fell over, the smoke was pretty thick! So, I can say that so far plants are OK with a lot of smoke, lol. Either I left one of the little round ports open on top of the stove or a piece of wood popping knocked it loose.

Berengaria,

You say that the difference in temps was about 20 degrees. Did you determine this based on actual readings from the greenhouse without heat?

I agree with Texasgrower about containerized plants. The other thing to think about is that your temp swings in the GH could actually be greater than the temp swings outside. Consider your marginal outdoor plants...it is not the below freezing temps that damage or kill them, it is repeated freeze/thaw cycles that sometimes do them in. That's why we mound leaves on our hydrangeas and plant our azaleas on the north side of the house around here. So if your daily GH temp swings are large, that could damage the plants as much as the absolute low temperature you maintain.

This paragraph contains various errors and bad advice (sorry, Gothqueen, nothing personal) so I am compelled to make some comments. First, humid air does not "stay warmer" than drier air. Humid air feels warmer to us because our cooling method, sweating, is less efficient. Second, watering at night may be OK in Florida, but in a northern area it is a recipe for disaster. At night, when the GH cools, the relative humidity goes up and the vapor pressure deficit goes down. If the temp drops below the dew point temperature, no water will evaporate inside the GH, because the air at that particular temp is saturated with water vapor. If you water at night, any water left on the foliage will fail to evaporate and thereby promote botrytis and other disease. Finally, heater efficiency has nothing to do with air temperature or humidity. Heater efficiency has to do with the type of heater (combustion, vented or unvented, electrical, etc).

If you are using humidity as a rationale for timing your watering, you would be better off watering in the morning.

I do like Gothqueen's plant list, and I grow many of those. Figs might be an addition.

Boy, I have to second SB's advice to not water in the grhouse at night. I never water in the evening-or even in the late afternoon, I wait until the morning to do all the watering/fertilizing. The wet foliage/soil at night is a definite receipe for a ton of different fungi, both foliar and root fungi. Also, roots do most of their growing at night, and they grow better with oxygen in the soil. Water displaces oxygen, so its better to water in the am and let the soil drain through the day.

Gothqueen, I love how you have your grhouse planted out-one day I am going to do the same with a grhouse, but I thought your grhouse was smaller? Like 20 x40' or 30 x40'? Just curious-I know you use the space to the max.

I generally shoot for a 15-20 degree difference between day (75-80) and at night (60-70, 70 is close to the heaters and where I do the propagating)

Whatever works for you guys, go for it. I water every "night" in the greenhouse at 4am for a total of 30 minutes (15 minutes per side to cover 1700+ square feet) and have been doing so since the greenhouse was built, 7 years ago, and it works extremely well for me.
I don;t have any problems with wet soil, fungi, or anything else like that. But all my plants were chosen because they are almost without exception RAINFOREST plants and like moisture, and lots of it. I don;t grow tomatoes, or roses, or perennial flowers or any of that stuff in there.
None of my plants ever succumb to disease, and I have never had a case of botrytis. I do have the occasional mealybug or scale infestation but that is about it.
The majority of what I have in the greenhouse are:
Rainforest understory palms
orchids (almost all mounted, intermediate to hot growers)
Heliconias
Torch gingers
Alocasias
Anthuriums
Jade vines
Hoyas
Monsteras
Philodendrons
Mango trees and Guava trees
Tropical flowering trees like Browneas
Bromeliads
Epiphytic cacti
unusual ferns
tropical gingers like Torch gingers and alpinia purpuratas

If it lives outside in zone 8 and above, it doesn;t get greenhouse space

I think it depends on what you grow, but, I stand by my methods, they work really really well for me

Over many years in zone 8b my personal low target has been 40F-same for the local Botanical Gardens and Master Gardener's green houses. We even over winter tropicals at this level, even the tropicals that are not supposed to go below 60F. do well.
I think anything below this would be risky if maintained for an extended time.

tigerlily! You really got my attention with "roots do most of their growing at night". How do the roots know it's day or night and why would it possibly make a difference to them since they are embedded in soil? My curiosity is killing me on this. I have never heard or read that before. Please educate me on this.

I have read all the info telling you not to water in the late evenings, but truth is, I water when I get to it. I make a small effort to do most in the mornings, but in all acuality I end up doing a good bit late in the day both greenhouse and outside. I haven't felt I've had any problems because of it yet. But gothqueen, 4 am is early morning, not night, didn't you know that? lol

Talking about humid air being warmer than dry.....I've never quite understood it, but does this have anything to do with why they spray the citrus trees and strawberries with water when it's going to freeze?

ginger,
The leaves "know" when it is day or night. In the light they photosynthesize--(produce sugars that are transported to the roots for storage)" At night, the roots are not recieving sugars so they "know" to send the stored sugars (carbohydrates) back up to the above ground part of the plant so it can grow. That is why artificial lighting on a 24 hour basis is a no-no.

Gingerlily, since you live the same warm southern climate like I do, think about it this way.

When a cold front is about to blow in from the West, the air here in FL is usually a lot more humid than the air in the cold front. When their cold dry air meets our warm humid FL air, it triggers rain showers and maybe thunderstorms. After the rain pushes through and the humidity goes with it and the cooler drier air of the cold front slides into place, that lack of humidity is a lot of what allows the air to really cool off here. If there is no cloud cover (clouds are moisture, remember) and the wind dies off, we have what is called radiational cooling where all the heat that was trapped on the ground during the day just vanishes into the atmosphere, because there is nothing to hold it here.

On the opposite end of the spectrum, when its warm here at night (no cold front) and the humidity is higher, like now, the humidity will be at its highest peak just before the sun rises. Usually its about 100% here in FL. As soon as the sun starts to warm the air, it also starts to dry it and the humidity starts to drop because it dissipates.

It's the same in your greenhouse. If the air is trapped in there and is moist and warm already, its easier to keep it at a higher temperature using less energy that it would be if it was cool dry air.

This is why I water at night, (or shall we say, before the sun rises?) To take advantage of that principle. I've never had any negative effects whatsoever from doing it this way. I have an overhead sprinkler system. Its just like getting a gentle rain, every night. Kind of like you would get in the rainforest.

We hiked through an area in Hawaii several years ago that is considered to be a rainforest area. It doesn't rain in the day. It starts when the sun goes down and rains all night, every night. Everything is lush and beautiful.