Extending the season vs full growth

I see many people in this forum talking about using a gh to extend the growing season.  Does anyone use them for full growth, I.e. year round harvesting? What is required to do so?  I am still looking at high plains desert, though inexpensive land in another area will easily change my mind.  I would like to be able to harvest year round.

Depending on your latitude 'full growth' may be impossible without artificial lighting.

That being said, depending on your climate and the construction of your greenhouse it's totally doable to 'overwinter' hardy greens and harvest the dormant plants all winter long.

Greenhouses are very common for year-round production, especially of greens but also of things like tomatoes -- totally depends on your climate or how much you want to heat the GH. The plants aren't dormant... they are growing. Depends on what you are growing and where you are. I know plenty of farms doing year-round greens with average lows in the teens in Jan-Feb, as an example. At those temps you need heat, but you can find sustainable methods.

Obviously the nice thing about the desert is lots of sun, so even with very cold nights you can take advantage of that by banking heat with thermal mass. Many threads on here about passive solar greenhouse techniques.

Eric Bee wrote:Greenhouses are very common for year-round production, especially of greens but also of things like tomatoes -- totally depends on your climate or how much you want to heat the GH. The plants aren't dormant... they are growing.

Are you sure Eric? I had heard that plants stop actively growing via photosynthesis once daylight hours reach a certain minimum limit.

Here within 300 miles of the canadian border that timeframe is from early february through late October.

I'd like to learn I've been misinformed on this, if that is the case.

Yes, I am sure. With the caveat that I am not a biologist and could well have some of this wrong:

Photosynthesis is dependent on light, obviously, and temperature (plus water, CO2 and Chlorophyll). Temperature influences efficiency of photosynthesis, so even if you had a long period of sun but very cold temps, the plant will go into dormancy (or just stop growing) to protect from moisture loss, etc. But it's also not a binary thing in many plants -- cold temps simply slow down the chemical processes involved, which is of course why things grow more slowly when it's cold, but the chemical reactions in photosynthesis will occur any time there is sunlight. This is not universally true -- fruit trees (and trees in general) go dormant after a sufficient number of chill hours and don't wake up until temps rise.

Perhaps you are thinking of photoperiodism. Some plant's growth cycles, flowering in particular, are influenced by the length of darkness. Yes, the night length despite the name -- it used to be thought that it was length of day and thus you have long-day, short-day and day-neutral plants, but in fact it's night. The classic example in some parts of the world is cannabis, which are short day (long night) and so growers will cover them up to force flowering.

I do know it's more complicated in that photoperiod influences photosynthesis in some cases, but I believe that's mostly in lifecycles of trees. So it could be that dormancy is induced or influenced by photoperiod in some plants, but I don't know enough to know which.

The upshot is, if you provide sufficiently high temperature such that photosynthesis can occur (and this is plant dependent), it doesn't matter how much sunlight the plant gets, it will grow. Obviously more sunlight = more photosynthesis, although there is a limit. This is easy enough to prove: Look up farms in your area that use a greenhouse for winter production.

I think it depends on the plants Kyrt.  

Some plants are very daylight sensitive, others like kale, favas, chard, lettuce, leeks, miners lettuce, chickpeas, barley, oats, wheat,  ... all the winter crops, will grow just fine here at the 49th (well, roughly 48th and a 3/4s ), all through the winter, if the temperature is high enough.  They grow slower than if they do when there is more light, especially because it's almost always cloudy in the winter here.  

I have things growing in my (mostly) unheated greenhouse all year long. Right now, it is sweet potatoes, tomatoes, teosinte, cacti, onions, and some herbs. The teosinte is growing in the greenhouse, cause it needs long-nights to flower. But by the time my nights get long, it is too frosty. So the greenhouse keeps them warm enough to flower at this time of year. In late fall, the greenhouse can keep oyster mushroom logs moister and warmer, leading to better fruiting.

As soon as I get the winter squash fruits out of the greenhouse, I'll be planting it to winter crops like kale and spinach. I'll chop those out when I need space to grow tomato transplants in the spring. After the tomatoes get planted out, it will be time for the hot-loving plants: sweet potatoes, okra, peppers, eggplant, etc.

Early Spring:


Mushrooms in the winter:

Seeing as our first frost this year was August 19, I will be doing most of my veggie gardening in greenhouses from now on, summer and winter.  They will just need good ventilation in the summer, and I' thinking a rmh in the winter.

August 19! Ouch!

Ours was Sept 21, right on schedule. Of course now we've had a week of 70s, also as per usual. In three weeks it will probably be 20F.

I know many here already know this but I wanted to add: for season extension floating row covers are really great. You can get the heavy weight (Agribon AG50 for example) and they will give you at least 8F of protection, or 20F if you double up. In my climate it works extremely well because our temps bounce all over the place. The caveat is that they are polypropylene but you can get many seasons out of them if you are careful. I use 1/2" metal conduit bent into hoops and rocks or sand bags to hold down the row cover.

We have spring and fall punctuated by sudden snap freezes (can range into upper teens farenheit), usually about three a season. Without these I could squeeze in from middle of March to middle of November in 'bare air' depending on what crops I am growing. (6b at altitude). And can easily make nine with a combination of approaches.

1) Microclimate. Areas that are heat gathering, not a place cold air can pool, sheltered to the prevailing winds and open to the South-East to South-West. I can get up to a grow zone more out of some areas. This helps with warmer weather crops as well, to get more production. You can build a Hugel or berm in a sort of "U" with splayed open end to give you something that will collect solar heat and radiate it back.

2) Coldframe. Made of bales and old windows, or even sheet plastic (at least 4 mil), and again back/high side into the northerly direction. It needs a night cover of some sort for best results. Bales can be used for pee-bales after it gets warm enough to dismantle a bale perimeter coldframe. Add a windbreak.

3) Hoop house. I have two versions, one is to put a 40' raingutter heat tape into the ground at least 8-12 inches down then put the frame over made of PVC, duct tape, and sheet plastic; the other is without. Both gain at least one brooder light and a lot of gallon jugs of water for heat sinks. (takes 6 10' pieces of 3/4" thinwall pvc, 10-12 pieces of rebar, a marker, and 1/2 a 20'x25' sheet of at least 4 mil clear plastic, cut into 12 1/2' x 20' pieces). The frames I build are about 5'x8' and you can kneel insde them to work. Add a five gallon pail of water, open, for humidity and to warm up for afternoon watering. If you put in a ground heat tape, add one 250 watt brooder light (clear/white) with metal reflector and a CERAMIC socket. I wire it dead center. If you don't add two brooder lights. Keep extra bulbs. Drippage will kill them. You don't need to cover them, but do add a windbreak.

4) Windbreaks. I put in metal fenceposts (sturdier than T posts) then put metal garden fence or calf panels up then cut cheap blue tarps and put grommets to make them neat and wire them on taut. I have a few panels with tarp cover that I can move as we have a prevailing winter wind direction but sometimes the worst storms come from a different direction and the windbreak is crucial to maintaining temperature and sheltering plants.

5) Double walled greenhouse, with two separate airtight layers of sheet plastic. I built wooden frames to hold up the roof, and built one 12'x16' and framed it with calf panels, then sheeted it with sheet plastic and hung an inner layer to give dead air.

6) Espalier fruit or nut trees to the south side of a warm building. It will give that tree a boost of maybe half to a full grow zone. It will also make it easier for you to build a solar retaining and dead air insulating leanto type cover if needed to help keep the tree from frosting especially during bloom and fruit set.

Floating row cover can be your best friend. You can use it inside your cold frame, hoop, or greenhouse.

Old plastic gallon water or milk jugs well rinsed can be filled with water and used for heat sinks (you can paint them black also) around a perimeter, or 2 liter soda bottles, also you can herd some of the soda bottles around a plant then cover with a five gallon pail or old feed tub (I use the latter quite heavily, for everything, they are about 18" diameter and 18" tall, I get them for free from a rancher here every spring. He is glad to clean them out of his feed area and I can sure use them. If they have not been cracked they hold water just fine.) for the night. You can also cut the bottom out neatly on the milk jugs and use them for individual cloches, just remove the cap during the day for venting. For young tender plants the slightly milky bit gives them about 30% sunscreen so in altitude it helps with sunburn as well. I also cut the tops out to use them for liquid transference with a handle, or to collect cuttings or crop in....

If you do not electrify your hoop do make sure you have good windbreak going, a night insulating cover, and use floating row cover and judicious use of water filled containers inside around the perimeter.

A very good book is https://www.amazon.com/Four-Season-Harvest-Organic-Vegetables-Garden/dp/1890132276/ref=sr_1_1?s=books&ie=UTF8&qid=1478745007&sr=1-1&keywords=four+season+greenhouse  this fellow shows and tells how he has an unheated on-a-track growspace and uses floating row cover within to grow stuff year around.

https://www.amazon.com/Winter-Harvest-Handbook-Deep-Organic-Greenhouses/dp/1603580816/ref=sr_1_2?s=books&ie=UTF8&qid=1478745127&sr=1-2&keywords=four+season+greenhouse is another one I own and recommend, but the first one is a book I thought was worth eating rice for a week to get.

A-hah! I found the thread where it was stated that daylength restricted Photosynthetic growth [though clearly that doesn't apply to carbohydrate growth from seeds or tubers.]

Here's the thread and Here is Johnnyseeds' page making the same claims and linked in said thread.

So this is bunk, we've confirmed that at least some plants will continue to grow from photosynthesis of any measure so long as they're warm enough?

So this is bunk, we've confirmed that at least some plants will continue to grow from photosynthesis of any measure so long as they're warm enough?

 That's the way it looks, Kyrt.  Here's something from the article in Johnny's you linked to :

Most plants do not grow when day length is less than 10 hours. Even if the temperature is kept within the optimum range — for example, in a climate-controlled greenhouse — most plants will just sit dormant until the magic 10 hours of light per day arrives.

 I believe it is safe to say that this is accurate, but perhaps the 'most' after the dash should be underlined and in bold, or simply italicized.  Some plants are going to do just fine (like those that R Ranson mentioned), but fine is relative to what it is capable of given the present daylight/darkness ratio.  The photosynthesis will be greatly increased, thus growth increased, as the days get longer than 10 hours, and the reverse as days get shorter, and some plants will simply stop growing, go dormant, or die in winter light conditions.  There is only so much growth that can happen with limited light, and some plants are simply not going to grow at all, like the basil mentioned in the Johnny's article.  Thanks for sharing that, by the way.  It was a good read.  

To answer the original question :

Does anyone use them for full growth, I.e. year round harvesting?  

 Just because a plant may go dormant, does not mean that it can not be harvested.  If one is planting crops in the late summer or fall and they are young as late fall progresses into winter and their growth begins to slow down or go into dormancy, that is fine. (Eliot Coleman says that younger plants are much hardier to deal with the cold)  Plant enough that you can harvest them all winter, despite the slower growth rate.  The warmer days, and the days with more light, they will grow, if they are the right species.  Lettuce, Kale, Chard, and many other early season greens can freeze solid, and still live.  Some of the more tender plants, like lettuce, will be mushy if harvested when frozen, but if left to thaw while still on the plant as a warmer day comes upon it, it will be solid and crisp again, and delicious (the cold winter air gives it some more sugars or something... definitely brings out flavor).  Some plants can only take such freeze/thaw cycles so many times before they are ulimately unrecoverable mush, but many can be harvested outdoors (with no greenhouse/row covers/cloches/cold frames) right into the winter where I live, and it get's pretty extreme up here some winters... though you wouldn't have known it this last week-it's been stupid warm for November.  Some locations have too many freeze thaw cycles during the winter, and so some outdoor annuals can not easily stand up to it.  There are bound to be some that can.  Save those seeds.  

Another season extender that I've been told about from the Newfoundland bush, is to leave summer planted brassicas in the garden, but surround and cover them with spruce branches, and let the snow pile up over it to insulate it.  When a person wants broccoli, just go over to the spruce mounded row, knock the snow crust and insulation off, and then pull the spruce insulation back, and harvest.  I've yet to try this, but look forward to giving it a go sometime, when I have more time.

I wonder, if anyone tried hot beds, made with decomposing manure underneath the soil? There is a book published in UK about it by Jack First. He says, that it was used extensively in France before WW1 to grow lettuce and other crops commercially. I think those beds could be put in the ventilated green house for added warmth.

I am harvesting one type of plant that has a different strategy.  New Zealand spinach makes small leaves in warm temperatures and bright light. But now that I am down to about 8 hours of light and cool temperatures I am getting leaves the size of my hand. Here is an example of harvest plan when day length limits growth.

Google 'walpini'

Nathan Surendran wrote:Google 'walpini'

Walipini, in ground greenhouses. When set up properly they do not need additional heat. I am behind in building one, but plan on doing so (two actually) and putting an RMH in one. In case of power out or a long storm I can keep things going then.

https://www.niftyhomestead.com/blog/underground-greenhouse/  has a lot of useful links to get you introduced to the concept. And near the bottom, a few bale coldframes.

Full disclosure on the Walipini, it was engineered for low latitudes with a comparatively overhead sun.

It doesn't really work out well in high latitudes [unless done into a south-facing slope of significant grade.] You wind up with growing beds and soil thermal mass that are shaded most of the day.

I suppose the photoperiod thing should be a separate thread. So sorry for the thread drift, but it seems an important question to me.

Lynn Byczynski is certainly well respected in this field, but the article strikes me as a gross generalization. Perhaps there is some confusion about photoperiodism and it's impact on vegetative growth vs. flowering cycles. Clearly, the statement "Most plants do not grow when day length is less than 10 hours. " is neither precise or accurate. She discusses flowering and growth cycles as if they were both dictated by photoperiod when at the least that is very species specific.

I know this statement is not true because I grow in a greenhouse all winter long without supplemental light, as do many others. Even right now our day length is about 9:55 but because we are having a very warm November there is a ton of growth outside -- everything from grasses to brassicas to ornamentals. Obviously, growth increases as day length increases and vice-versa, but that is a question of how much light the plant receives and is entirely different from saying growth is dictated by photoperiod. If it were, then there would be a range where that growth would slow or stop and yet we cannot say that exactly.

So my take is this:
1. Vegetative growth is dictated by environmental factors such as temperature and by other periods in the life cycle of the plant. For example, many plants will switch from vegetative growth to flowering when certain conditions are met, and not have vegetative growth after that.
2. Flowering in all but day neutral plants is dictated by photoperiod.
3. Vegetative growth is not universally governed by photoperiod directly, although of course the amount of growth and degree to which it is possible is dependent on the amount of light the plant receives.
4. Dormancy is induced by temperature, but in some plants coming out of dormancy is dictated by photoperiod, which makes a lot of sense because you don't want a switch in cycle unless there is enough light.
5. Since temperature, especially in northern climates is most frequently dropping with shortening of photoperiod, it may seem that photoperiod dictates growth, when in fact it's temperature and/or the natural lifecycle and internal clocks of the plants.

In researching this to make sure I wasn't blowing smoke, I've seen many references in online articles to photoperiod controlling growth cycles but in the scientific literature distinctions are made, specifically that photoperiod will induce flowering which then stops vegetative growth. That sort of thing.

I have this book "How Plants Work" by Linda Chalker-Scott, she says "...true dormancy is controlled by the internal clock, rather than by some environmental factor like sunlight or water." One thing she notes in this book is that plants with small seeds (and thus less energy reserve) tend to have photodormancy, but that means they wake up from dormancy with a certain amount of light, not the other way around.

She also has this to say (talking about seeds though):
"For seasonally dependent photodormant plants, the presence or absence of useful sunlight is not the only trigger controlling germination. They also need a clue to what time of year it is. As gardeners know, rainfall and temperature can vary wildly throughout the year and even from day to day. Plants need a more reliable system of figuring out when it’s time to start growing."

Joy Oasis wrote:I wonder, if anyone tried hot beds, made with decomposing manure underneath the soil? There is a book published in UK about it by Jack First. He says, that it was used extensively in France before WW1 to grow lettuce and other crops commercially. I think those beds could be put in the ventilated green house for added warmth.

Yes, I have done this in a greenhouse and still do this more often than not when making raised beds outside. Typically raw horse manure and straw, covered by 6" or so of finished compost/soil. The sides of the raised beds I construct to provide some air. I never read a book about it, just did it after reasoning it made sense but my results, while worthwhile enough for me to keep doing it, don't provide the kind of warming action I hoped for. I will have to look for that book to see if I'm doing it wrong or if that's just the way it is.

Let's move the daylight conversation to here.

It's such a fascinating topic, well worth investigating.  

Deb Rebel,
  Thank you for point number four you made, windbreaks! It had never occurred to be as a possibility to extend the life of plastic on hoop houses, AND help retain internal temps. We currently are doing the pvc frame staked on rebar w/ 6 mil plastic. I don't like the idea of plastic, but it's the option we have now. Also, when parts of it tear, it can be cut up for smaller cold frames, window insulation, etc. Anyhoo, WINDBREAKS! Next stop at Goodwill, I'll be picking out whatever sizeable fabric I can find for said project. What a low tech no brainer!

casey lem wrote:Deb Rebel,
  Thank you for point number four you made, windbreaks! It had never occurred to be as a possibility to extend the life of plastic on hoop houses, AND help retain internal temps. We currently are doing the pvc frame staked on rebar w/ 6 mil plastic. I don't like the idea of plastic, but it's the option we have now. Also, when parts of it tear, it can be cut up for smaller cold frames, window insulation, etc. Anyhoo, WINDBREAKS! Next stop at Goodwill, I'll be picking out whatever sizeable fabric I can find for said project. What a low tech no brainer!

Here we have average sustained winds of 25mph. This means you have to engineer everything to survive. And even in growing season, windscald can make it hard on your crops. If I buy cheap blue tarps, then a grommet set (Harbor Freight) and cut, fold over, and grommet to size my tarps I can get 2-3 years use out of them. If they do not flap they do not fray. It is a painful long process (my opinion) to do a grommet setting session but by doing so and spacing them (or adding more) to make sure the tarp is fastened down with no vibration, no flapping, and a few strategic paddings where needed so things won't rub through, I get a long use out of those tarps. Buy a big blue tarp on sale and cut it down to what you need. Most of my windbreaks are about four feet high. If you are grommeting into a raw edge, fold over then grommet, giving it that reinforcement of two layers and preventing the edge presented to the wind to be raw as that will whip out and ravel off in no time.

I grew competition pumpkins for some years and these are all the secrets I learned growing one of those large plants (30'x30' plot, and some edge/border plantings inside the windbreak fence as it only took up about 750 square feet of the 900 allotted) Put your windbreak 2-4 feet away from your hoop or greenhouse, so you have room to get around it, and it won't block much light that way. No more than 6 feet away. Even if your greenhouse is taller, 4 feet of windbreak will make a huge difference when trying to hold temperature at night.

Fabric for night covers? Thrift store and rummage sale blankets. It doesn't matter if there's a bit of stain, frayed edge, or a small rip or hole. Just darn those up and they make great covers. Do realize you have to take them off every morning (within an hour of sunup) and hang them to dry out. They always get night dew. Then by dark, usually I do within an hour of sunset before sunset, put them on. I have a huge pile of frost blankets I have collected over the years and spouse knows better than to touch them. A favorite is old electric blankets, even though they have that wiring in them, they often go dirt cheap and they will never be plugged in again so it doesn't matter. Taking them apart to get the wires out is NOT worth the effort.

Also on a very cold or high wind night you might put floating row cover or at least an old sheet over everything on the windside of your shelter, inside. This will gain you that much more in keeping heat on the plant. Do make sure any inner covering does NOT touch your outer wall or the heat transfer will be immediate. (as in it will bleed heat). I also put my heating source on the windside third of the area to help even out the overall heat.

Eric Bee wrote:

Joy Oasis wrote:I wonder, if anyone tried hot beds, made with decomposing manure underneath the soil? There is a book published in UK about it by Jack First. He says, that it was used extensively in France before WW1 to grow lettuce and other crops commercially. I think those beds could be put in the ventilated green house for added warmth.

Yes, I have done this in a greenhouse and still do this more often than not when making raised beds outside. Typically raw horse manure and straw, covered by 6" or so of finished compost/soil. The sides of the raised beds I construct to provide some air. I never read a book about it, just did it after reasoning it made sense but my results, while worthwhile enough for me to keep doing it, don't provide the kind of warming action I hoped for. I will have to look for that book to see if I'm doing it wrong or if that's just the way it is.

Very cool. How deep was your used manure? If I remember correctly he says it has to be 2 feet deep at least for 2-3 months of warmth. He also waits 5-6 days for the heat to stabilize a bit, because at first it will be too hot. Manure has to be not older than 6 weeks to heat well. He also says leaves can be mixed in as well. I think book is worth buying. It is not a large book, but no fluff, all specifics of his experience.
 What kind of things did you grow and did you use cold frame on top? In what outside temperature?

The first one in a greenhouse was a bit over 2' deep. Very fresh manure. It certainly did get hot the first few days, but I was expecting it would last longer. I don't recall exactly, but it was my sense that after less than a month it was only a few degrees over ambient air temps. This was in the dead of winter in the high desert, so temps got as low as 10F. I also used thermal mass to keep the greenhouse stable, so it's difficult to say exactly the effect of the raised bed. No cold frame, but I did use a row cover. In the winter it was greens and asian veggies then come spring I put in tomatoes, which really did brilliantly.

I think it's a really good idea and will some day experiment more because I know others who have used this method with great success. But at the end of the day, it is kind of a one-shot deal unless you want to dig out the raised bed every year. Oh, I can think of great ways to make that easy -- maybe open a hatch and spill the stuff in an area close by. Strikes me as work.

Maybe it was not big enough, I can't remember all specifics, but he did give minimum size as well. However he gardens in England, so cold is gentler most likely. Maybe you could just leave spent manure as a raised bed and plant it? Did you use horse manure. I think he says horse is best, but I can't remember why.