Tomatoes are fundamentally perennials. If you can keep them alive over the winter, they'll produce nicely the next year. Actually, I believe that you not only have to keep them from freezing, but you need to keep them nice and warm. The decade-old and highly productive tomato trees that I've heard about are maintained at temps around 70F. I've overwintered peppers, tomatoes and eggplants and they seem to do OK even after having been exposed to temps in the 30s, but I'll bet they'd be stronger and more lush if they weren't abused in that way.

I suspect that container plants will have their own challenges in overwintering.

"If It's possible to do it, will I need to provide extra UV lighting or heat?"

Don't know for sure about heat in your location but I do here for sure and the odds are you will need to provide at least some supplemental heat. Tomatoes are what is often called a hot greenhouse crop, not a cool or cold GH crop.

Yes, lights are also needed. Lights that provide not only longer hours of light but fuller spectrum, a better spectrum than the plain old fluorescents used to grow seedlings. You can learn much more about that aspect over on the Growing Under Lights forum here and you'll also find many past discussions about the other issues on the Greenhouse forum here.

And therein lies the problem - the costs of equipment, power/fuel, automated monitoring, lighting, etc. Sure it is possible to do but many find the overhead cost often becomes prohibitive, unless cost is not a concern.

Dave

if it were something like peppers (especially bells) i'd say for sure since peppers generally grow slower. second year typically results in bigger yields and more peppers. the plants can grow quite massive and can actually thrive for half a dozen years if well cared for. peppers are also a higher value crop so it's worth keeping around if possible.. tomatoes grow so fast that i probably just start new plants.

Thanks guys!

I don't like the idea of buying/setting up/maintaining extra equipment. I guess I will just try my best to keep one or two plants in the greenhouse starting in October and see what happens! Perhaps I'll put one mature plant and one new plant and see how that works.

I just can't stand store-bought tomatoes after being spoiled by home-grown.

Even if I get an extra month of tomatoes... I'll be stoked!

I grow tomatoes outside over the winter here, I'm sure they'd do even better in a greenhouse. Mine produce, but slow down compared to summer tomatoes, I'd imagine they'd do well for you with the extra heat a greenhouse would provide.

I highly respect the posters that are suggesting extra light and heat, but I don't think you'll need them, honestly. As I said, I grow tomatoes unprotected outdoors over the winter and they will fruit and continue growing unless we get some sort of freak frost (extremely rare where I am, I'd assume you're the same) - which your greenhouse will protect from.

I do generally start new tomatoes in July or August to overwinter, as my summer tomatoes tend to get smacked pretty hard by bug damage over the summer. Any that survive the summer fairly unscathed get to stay, but must of my winter tomatoes are usually new starts. I don't know how they'd do if I tried to dig them up and move them, though, I probably would just start new - just make sure you start early enough that they get some good growth before it cools down.

Oh, you're talking abut *production* over the winter, and not just *survival* over the winter. Yep you need fake summer to do it right. Lots of light, heat, etc. Probably cheaper to import your fruit from way down south. That being said, be aware that a lot of commercial tomatoes are farmed indoors (we have hundred of acres of tomatoes farmed under glass out in West Texas) but the price you pay at the store tells the tale.

Yeah I assumed in my comments that you wanted production, not just plant survival. Also not all GHs are created equal by any means. Lots of things are called a greenhouse. So one can't assume that any GH will function the same or give the same results even in the exact same location.

Dave

I've lived in the LA area, and the mean temps there run from about 60F to 70F. So tomatoes outside will survive, and will probably fruit in the winter, but will still grow pretty slowly. I think I once tried to grow tomatoes outside there in the winter, and was disappointed. Yes, a greenhouse without a heater might actually work well, however. You could probably keep the winter mean temps in there in the 70s with sunlight.

But again, as I said, if you do it in a greenhouse you're doing container gardening, and that's a whole different ball game.

Yeah, the containers can change the game, I've never tried overwintering container tomatoes. I do overwinter container peppers outdoors and they do ok - not great production but they do produce some. I just think (and I could totally be wrong) in an unheated greenhouse in coastal CA, you'd grow enough to have something to eat over the winter, and probably more than something. Dangit y'all, now I want a greenhouse.

You may well be right Humsi but as you say it is counter intuitive to common experience in the GH industry nationwide. I know several commercial GH growers in the CA area and can only attest that they use supplemental light, heating, and cooling equipment in their commercial GHs just as we used to here until we changed our focus to cold GH crops about 6 years ago (and reduced our overhead by 2/3). And I would assume, right or wrong, that a home model GH would need them even more.

But the only way to know for sure, given all the variables, is to try it in the specific situation and see if it works and what the problems and costs might be. That or meet and talk with some local GH growers.

Dave

I understand. I'm just assuming based on the "coastal" part of the OP's post, and the fact that his description of his winters sounds identical to mine - "We have mild winters here with only a handful of nights colder than 40 degrees. Lots of sunny days in December/January/February." So I'm coming at it as if we are gardening in very similar climates, and since it works for me outdoors, I do think it would work for him in with even warmer conditions provided by the greenhouse. If you're in inland California, it can definitely be a very different story (colder temps, bigger temp swings, frost, etc).

Just sharing my experiences/thoughts since it does sound like the OP and I can do similar things in our climates in winter. And I definitely don't want to come off as argumentative, just as encouraging to the OP.

I have to wonder if the constraints on commercial wintertime GH tomato growers isn't a little different, That is, I suspect they want to contract winter harvest and delivery of a certain volume on a specific date. If you want to do that, you need to control your temperature and humidity (with heat, ac, etc.) and even supplemental lighting extremely carefully. The cost of doing that is absorbed in the specificity of the contract. You also farm determinate, rather than indeterminate, varieties. If you do it right, *bang*, on February 15, I deliver to you a ton of tomatoes. If on the other hand you allow the temperature to slop ten degrees one way or the other in some generally optimal range, and get whatever illumination the clouds allow, you'll get a nice harvest but won't have much control over volume of harvest and harvest date.

Humsi, or anyone with the knowledge-

Around what temperature is too hot for a Tomato plant in the greenhouse? I assumed it wouldn't be to hot over winter because I thought they loved heat a lot.

There's so much to learn! Thanks for all the feedback guys.

I'm finding that one friend I have who went to school for commercial growing seems to be slightly off with their advice...however the other friend of mine who learned on her own by experimentation at home seems to be right about everything. Perhaps it's because she went to school in an inland city where it is a bit cooler over winter? Or she learned how to grow massive amounts?

I'm glad I have both friends though because each brings up different points and concerns I need to think about. Essentially I'm only growing for personal use (lots though, I eat at least a half cup of Cherry Tomatoes and 1 full-size Tomato in a day). There are lots of hungry family members around and neighbors that probably love tomatoes as well though. I'll never have too many!

Since I don't have a greenhouse, the only advice I can give is what I *think* I would do if I did. I would probably only close it in the evening and open it up in the morning after it's warmed up a bit. If your winter days are like mine, it can get up in the 70's-80's during the day, which is perfect for tomatoes to set fruit. If they were in an enclosed greenhouse I'd think you'd be looking at 90+, which will cut down on your tomatoes setting fruit. I'd probably leave it closed during the day on those rare times that we get a cold snap. Again, my advice on this is all theoretical, so take it with a grain of salt. You're probably going to have to do some experimenting.

You also may want to experiment with the type of tomatoes you decide to use for winter growing, you'll find some types do better than others. If you're wanting to get lots of tomatoes, the more plants you can fit in, the better, as production will be slower than during the summer.

Yes 90+F temps are unfriendly to tomatoes. The plants will do great, but the flowers won't set fruit. They'll just fall off. The pollen gets too sticky to drop properly. In my area, high tomato season is May-June. In July, August, and even September, it's simply too hot here to get any. Some varieties are a little more forgiving of high temperatures than others. I doubt you'll ever see 90+ temps in a greenhouse in the winter where you are.

Again assuming his climate is like mine, we've been having some weird winters the last couple of years. The last two years, in my area, we had a a few weeks of high 80's-low 90's during February. It's fairly normal to get a couple of days here and there with those temps throughout the winter. It happens, which is why I mentioned making sure to keep track of what's going on in that greenhouse, temperature-wise, as I'm assuming those temps outside would be pretty hot inside a closed greenhouse.

Thanks again, guys! Yes, we do get one or two days randomly of 80+ degrees usually in January, February and in March too. The annoying thing is that usually it's very unpredictable! The weather forecast will say 72 degrees and bam!...by 2:00pm it's 82 degrees.

I like the idea of experimenting. I'll probably experiment with different types of plants and also keep one outside in the day and one inside the greenhouse to see if that effects fruit set!

Any advice or suggestions about thermometers? A certain type or brand? I've never bought one before.

The problem in greenhouses is the magnification of temp that happens. 80 degrees outside air temps can easily mean 120 in the GH. it varies depending on what the GH is made out of - glass .vs. poly carb sheeting vs. double wall or triple wall, etc. So you have to learn - with lots of thermometers or monitors - how well your particular gh modifies the outside temps - insulates against cold and intensifies outside warmth..

We have 4 and every single one of them has different ranges set on the controls simply because of their location relevant to each other and other structures.

And yes Dan is absolutely right that the commercial approach is very different but there are still some issues in common.

Dave

PS; sorry but I thought the OP said he was in No. California rather than central as his user name indicates so I thought the climate would be very different there than in the south. CA is so big compared to the rest of us - except for those Texans - we tend to think of it a 4 different states rolled into one. :-)

Well, I don't think that brief periods of 90+F are anything to worry about. If the current flowers are damaged, it won't be long till others come out.

As to thermometers, a cheap ten buck digital one would be fine. Get one with a remote probe -- and indoor/outdoor one. You can use that probe to test soil temperatures, and put it under your lights where it might be hard to read a thermometer.

I know this is an old thread, but @TomatoZesty 9B Central CA:Coastline if you are still on here, how did it go? I am also on the central coast (San Francisco Bay Area, Alameda county), zone 10a, and just ordered a small poly tunnel/pop up greenhouse. I, too, am planning to try growing tomatoes over the winter. I grew all my vegetables in grow bags this summer, so I can just drag the ones I want to keep into the greenhouse. Just not sure if I'll need to add lights to keep the tomatoes growing. The greenhouse will be oriented East/West so the long side will get southern exposure. The north side will be protected by a fence. it's the warmest, sunniest part of my yard, and I'm hoping it will be enough to keep my tomatoes, peppers, and strawberries going. Please share what happened with your tomatoes!

I live in the Bay Area of California, and I have a very small "farm", consisting of a special light installation in our garage, and a hard plastic greenhouse and a small outside space with excellent sun. I grow tomatoes, potatoes, peppers, passion fruits, strawberries, and hanging geraniums all from propagation (suckers, slices, stems.) In addition, basil is easy to grow from seeds, plus we have a couple of orange trees and a lemon tree. I grow everything in containers.

I have started to propagate all the veggies and fruits from above right now in September and October, not necessarily for winter consumption but to assure an early start in the next year.. From a package of Sugar Bomb tomatoes bought at Whole Foods in May, I took 8 tomatoes, sliced them, put them in fertile soil, watered them, and lo and behold they came up and provided me with 20 extremely well producing plants right now, in October. The same with a red pepper from Whole Foods. I used the same procedure, got about 12 plants that are now producing about 75 peppers. I learned that the only difference in color is growing time, so I let them grow until they are all red (and very firm.) I started their growing quite late in early July.

I just did the same thing again with resulting tomatoes and peppers from above, and am already propagating them. They have already come up, and I plant to put them in bigger containers in the greenhouse over the winter.

In addition, I have cut a number of strong suckers from other tomato plants, including hybrids, and they are all growing roots. Again, I will put them in bigger pots in the greenhouse during the winter.

My goal is to plant them in their final and larger containers during early April and start picking the results in early June.

Just read and try. It is so much fun, and it has kept me sane during this pandemic.

I grow most of those, too. Currently have 5 different kinds of passion flower vines growing and two more recently rooted. I've also rooted some pepper plants, early girl tomato, and several flowers from the favorites I've grown this summer. They are all doing well. I am just interested in experimenting with winter production in portable greenhouse. I bought a solar panel and solar generator to power a few low wattage LED grow lights. I'll place one over each of the food plants I'm hoping to grow. The solar generator should produce enough power to keep the lights on about hours. But before I even put up the greenhouse, this crazy weather has to cool down. Never experience anything like this summer in the bay area and I grew up here.

Thank you, Tastie. Can you tell me how you propagated your passion fruit plant?