Do You Really Need to Heat Your High Tunnel in Winter? (Plus: Irrigation Tips for Non-Standard Bed Layouts)
By Jonathan Dysinger and John Dysinger
Updated on
Show Transcript
0:00Hi guys, Jonathan here with Farmers Friend and I'm at Bountiful Blessings Farm with my dad John and we're going over some questions that have been submitted from our customers and we have
0:09uh a couple of questions from Nancy. She says, "I bought a high tunnel and it got much colder than I thought it would over the winter. Do you have any tips
0:18non-electrical for warming it up during cold nights? I tried straw bales around the outside and passive water barrels on
0:25the inside. This summer, I hope to install sand paths with red tile pavers to help capture heat. Other ideas? What do you think? Non. So, I'm non-electric,
0:36but probably sounds like she's looking for something pretty passive, like not not uh gas or wood or, you know, something
0:45like that. So, you know, I hear from people all the time about all these elaborate things they're doing to to
0:54create thermal mass and and to try to hold heat in there. Um, but the thing I
1:01always ask is what are you trying to grow?
1:05Um, you know, if you're if you're not trying to grow warm weather crops, which
1:12I hope you're not, because I I think that's kind of a a bad idea from my personal experience to grow things
1:20totally out of season. Though, if you're trying to grow cool weather crops, there are some hardy crops which really don't
1:29need all those elaborate things. And so I I think people kind of go further than
1:35they need to. And again, you can't buy a a basic high tunnel and expect to grow tropical, you know, fruits in it or
1:44something. Yeah. I mean, you'd have to have a glass structure with with heat and all that kind of stuff. Yeah. with what what you have figured out, Nancy,
1:53it sounds like is that a high tunnel, if it's a single layer of plastic high
1:59tunnel or hoop house, um once the sun goes down, the inside temperature
2:06is, you know, at best one or two degrees, maybe 3° warmer than outside.
2:14So, it really is not giving you a lot of protection just from that plastic. Um, but again, I I I like to
2:23refer to books. This is the classic on winter growing, Elliot Coleman's Winter Harvest Handbook. Um, he was the pioneer with winter growing. He's up in Maine,
2:36the coast of Maine, but he's he's in zone five, but he's doing growing all through the winter in unheated houses.
2:46And that book tells you, you know, it's all about the crops. You grow things like spinach and kale and there's a lot
2:55of Asian greens, clonia and minotina and you know all these
3:03things can handle some really cold temperatures. Um below freezing temperatures. Oh yeah,
3:10well below freezing. Um, and in fact,
3:14I'll just say the the key to that book and to basic winter growing is to
3:21combine the one layer of plastic on the hoop house with a low layer of row cover
3:30over some kind of wire hoops or something. And that that row cover ideally you pull it off during the
3:38daytime so the sun can be heating the soil, warming the soil through the plastic and then in the late afternoon
3:46you pull the row cover on and that traps that ground heat under there. Yeah. So,
3:52that's a simple explanation, but yeah, I I would question whether you need all those fancy solutions to to grow cool weather crops.
4:05Yeah, if you're trying to grow lemons through the winter, you you're going to need heat. Um and more than barrels of
4:14water, more than any kind of passive thing is going to give you. Yeah. um you know digging into a hillside or something like that you know you that'll
4:22better you know I mean you can use the ground heat if you want to get fancy and spend a lot of
4:29money you can geothermal and stuff like that yeah yeah those work yeah another book just um
4:38JMFier's the winter market gardener has just come out in the last couple years it's another
4:46excellent resour source on winter growing. And he talks more about they've been experimenting with geothermal
4:53running tubes through the soil and stuff. Yeah. So, those are possibilities, but are they needed? You know, we don't know where you live,
5:03Nancy. That would have been helpful. But just to wrap that up, figure out what kind of crops you want to grow and be
5:10realistic about what those crops are going to require. um cool weather crops that can handle freezing temperatures
5:17and and just bounce back. That's generally the way to go if you're just growing in basic high tunnels.
5:22Otherwise, you're going to have to do some sort of significant heat source to be able to uh keep those warm temperatures for warm weather crops. So,
5:30all right, we had one other question um from Nancy. She said, "My my second question has to do with irrigation. I do not have my paths in straight rows, so
5:39I'm having some issues with figuring out water path. My first attempt has been a dismal failure with only the drip area getting damp and water not reaching the plants. Your system is great for rows,
5:50but what if the beds are not in rows? So, yeah, I'm envisioning like a uh a greenhouse with, you know,
5:58wandering paths and and different tropical trees. NY's an artist or a, you know, a creative person rather than a
6:08functional person. Yeah. Form over function. or over function. So yeah,
6:15that it it is definitely a little more complicated than straight rows and beds.
6:21And obviously that's why market gardener, you don't see too much of that wandering rose in market gardening.
6:31Um but hey, you know, if if you're not into it just for the money, you know,
6:37it's beautiful. And yeah, so regular drip um like the the tape drip tape that
6:44we use is harder to to kind of meander around stuff, right? But what about like that traditional kind of soaker hose?
6:53Soaker hose that I mean that should work pretty good. I have really no experience with that, so it's hard to talk to it um
7:02intelligently, but it would seem like that would work fine. You know, what I don't know is what kind of
7:11um you know, how much water it's letting out and if it's even over the whole length of the hose. Yeah. Um but it
7:20sounds like from the question that she did use drip. And I I think, you know,
7:27you could curve drip tape some. It doesn't have to be. I mean, it'll kind of kink a little bit, but as long as
7:34it's not totally kinkedked, you're still going to be getting water through there.
7:39But I think there's also a a misunderstanding about drip here that probably a lot of people don't
7:47understand. She says um the drip area is getting damp and water is not reaching the plants.
7:56So, one thing it's important to understand about drip, you know, drip tape, it's just where where it's
8:03dripping into the soil. You may have a very small area that is actually moist, but as it goes down, it spreads out.
8:12Mhm. And so you don't necessarily have to get the whole surface wet unless you're trying
8:20to to germinate seeds, which is not good to do with drip tape. Um, so I would
8:29encourage you just to experiment and dig down a little bit with your finger and you might find that you're getting
8:36better coverage than you thought just under the surface of the definitely cones out. I mean, the other thing with drip tape is you have different emitter
8:45spacing. So, you know, if you've purchased a drip tape that has, you know, a wide gap between emitters, that could be a problem, too. You may need to get something that's a little closer.
8:54But, you know, if you're trying to do really, you know, snaky paths or or beds, I would say probably look into soaker hose. That's a a hose, you know,
9:04about I'd say, you know, half inch to 3/4 diameter that is just almost uh kind of foamy. Uh, you know, it just kind of
9:13emits water out the whole recycled tires or something. That's I think it's rubber. Yeah, it's it's rubbery, but it
9:21just kind of emits water out of the whole hose. Um, so I don't It's a good question. I don't have any firsthand experience with it as far as what the,
9:29you know, GPH per linear foot and stuff like that. I'd have to look into that.
9:34But that seems like the best option there other than some sort of overhead,
9:39which you know, Farmer's Friend sells overhead kits for in tunnels where it's just a sprinkler, micro sprinkler that
9:46gives you a nice consistent even coverage. Now, that's going to yeah,
9:49that's going to cover your pathways and everything. But depending on what you're trying to grow and if if the plants that you're growing are okay with getting a
9:56lot of water on the foliage, that could be a good option as well. So couple of couple of options there, but definitely
10:05um traditional irrigation methods are more challenging if you have um a lot of contours, meandering pathways,
10:12meandering pathways and and beds. So all right, if you have been watching this and you have a question on on your mind that you would like for us to address in
10:21a future video, feel free to click that link down below and submit a question. Until next time, happy growing.
A single-layer plastic high tunnel only adds 1–3°F over outside temperatures after dark — so if you're growing cold-hardy crops (which you should be), elaborate heating schemes aren't necessary. The proven approach is Eliot Coleman's two-layer system: one layer of plastic on the tunnel plus a low layer of row cover over wire hoops inside, pulled on in late afternoon to trap ground heat and removed during the day to let the sun warm the soil. For irregular bed layouts, soaker hose or overhead micro-sprinklers may work better than drip tape, which is designed for straight runs.
We get a lot of questions from customers, and two recent ones from Nancy touch on challenges that many growers face — especially those in their first or second year of tunnel growing.
My dad, John Dysinger, has been growing year-round at Bountiful Blessings Farm for over two decades. Here's his take on both of Nancy's questions.
Do I Need to Heat My High Tunnel in Winter?
Nancy wrote: "I bought a high tunnel and it got much colder than I thought it would over the winter. Do you have any tips — non-electrical — for warming it up during cold nights? I tried straw bales around the outside and passive water barrels on the inside."
This is one of the most common misconceptions about high tunnels, and my dad hears it all the time. People invest in elaborate thermal mass strategies — water barrels, sand paths, tile pavers, straw bale insulation — when the real question they should be asking is: what are you trying to grow?
The Reality of Single-Layer Tunnel Temperatures
Here's what Nancy discovered firsthand: a single-layer plastic high tunnel provides very little temperature protection after the sun goes down. At best, you're getting 1 to 3 degrees warmer than outside air temperature. That's it.
During the day, when the sun is shining, the tunnel traps solar heat effectively and temperatures can spike well above ambient. But once the sun sets, that heat dissipates quickly through the single layer of plastic. All those water barrels and straw bales? They help a little, but they're not going to transform a basic tunnel into a warm growing space on a 15-degree night.
The Question That Matters: What Are You Growing?
If you're trying to grow warm-season crops through winter in an unheated tunnel — tomatoes, peppers, tropical fruits — no amount of passive thermal mass is going to get you there. You'd need a heated glass structure or significant energy input, and as we've discussed in previous articles, Bountiful Blessings Farm tried heated winter tomatoes once and didn't harvest enough to cover the propane bill.
But if you're growing cold-hardy crops — spinach, kale, lettuce, carrots, Asian greens like claytonia and minutina — you don't need all those elaborate solutions. These crops can handle temperatures well below freezing. They freeze solid, thaw when the sun comes out, and bounce right back.
The Two-Layer System: Simple and Proven
The key to successful unheated winter growing isn't adding heat — it's trapping the heat you already have.
Eliot Coleman pioneered this approach in zone 5 on the coast of Maine (significantly colder than most of the country), and it's detailed in his Winter Harvest Handbook. The system is straightforward:
Layer 1: Your tunnel plastic (already in place).
Layer 2: Row cover draped over wire hoops directly over your crops inside the tunnel.
During the day, you pull the row cover back so sunlight can reach the soil and warm it through the plastic. In the late afternoon — before the sun goes down — you pull the row cover back on. This traps the ground heat in a small pocket right around your plants, creating a microclimate that's significantly warmer than the open tunnel air.
That's it. No electricity, no gas, no water barrels. Just two layers of passive protection and the right crop selection. Coleman has grown through Maine winters for decades using this method, and my dad has done the same in zone 7 for over 20 years.
Farm Smarter, Not Harder
Join thousands of market farmers receiving regular insights on how to streamline your systems, save your back, and increase your farm’s bottom line.
When Do You Actually Need Heat?
If you want to grow warm-season crops through winter, you need a real heat source — and that means propane, wood, or electric heating in a well-insulated structure. Passive thermal mass strategies alone won't get warm-season crops through hard freezes.
Geothermal is another option — Jean-Martin Fortier's The Winter Market Gardener discusses running tubes through the soil to capture ground heat. It works, but it's expensive to install. The question is whether it's needed for what you're trying to grow. For cold-hardy crops, the answer is almost always no.
How Do I Irrigate Beds That Aren't in Straight Rows?
Nancy's second question: "My beds are not in straight rows and I'm having issues with drip tape. Only the drip area is getting damp and the water isn't reaching the plants."
This is a less common problem on market farms — where standardized straight beds are the norm — but it's a real challenge for creative growers, permaculture-style layouts, or greenhouse setups with winding paths and mixed plantings.
First: You Might Be Getting Better Coverage Than You Think
Before changing your irrigation system entirely, my dad suggests checking what's happening below the surface. Drip tape wets a small area on the soil surface, but the water spreads out as it moves down through the soil profile. If you dig down a few inches with your finger near a drip emitter, you may find moisture coverage is better than the dry surface suggests.
This doesn't help if you're trying to germinate seeds — you need surface moisture for that, and drip tape isn't the right tool for germination. But for established plants with root systems that reach a few inches deep, drip tape coverage may be adequate even if the surface looks dry.
Also check your emitter spacing. If your drip tape has wide gaps between emitters, that could be the issue rather than the layout. Closer emitter spacing provides more uniform moisture along the line.
Options for Irregular Layouts
Drip tape with gentle curves. Drip tape can handle some curvature — it doesn't have to run in a perfectly straight line. As long as it doesn't kink sharply enough to block flow, you'll still get water through. Gentle sweeping curves are fine.
Soaker hose. For truly winding beds, soaker hose is worth exploring. It's a porous rubber hose (usually about ½" to ¾" diameter) that emits water along its entire length and can be snaked through curved beds much more easily than drip tape. My dad doesn't have firsthand experience with flow rates and uniformity on soaker hose, so you'd want to experiment and monitor coverage. But it's the most obvious solution for non-linear bed layouts.
Overhead micro-sprinklers. Farmers Friend sells overhead irrigation kits designed for use inside tunnels. Micro-sprinklers give you consistent, even coverage over the entire area — beds, paths, and everything in between. The trade-off is that you're watering the paths too, and foliage gets wet, which isn't ideal for disease-prone crops. But for hardy plants that tolerate overhead water, it's the simplest way to irrigate an irregular layout uniformly.
Why Market Farmers Use Straight Beds
This is a good moment to note why most market farmers standardize their bed layouts. Straight, parallel beds of uniform length make irrigation simple, cultivation efficient, and planning predictable. The functional benefits compound over time — every system on the farm works better when beds are consistent.
That said, not everyone is farming purely for profit. If your layout is designed for beauty, permaculture principles, or personal enjoyment, the irrigation challenge is solvable — it just requires different tools than the standard drip tape setup.
The Takeaway
For winter tunnel growing: focus on crop selection first, then use the two-layer system (tunnel plastic + row cover over hoops) to trap ground heat. You almost certainly don't need elaborate heating solutions for cold-hardy crops.
For irregular bed irrigation: check whether your drip coverage is better than the surface suggests by digging down a few inches. If you need a different solution, explore soaker hose for curved beds or overhead sprinklers for full-area coverage.
Both answers come back to the same principle: match your tools and systems to what you're actually trying to grow, rather than engineering solutions for problems that simpler approaches can solve.
Frequently Asked Questions
At night, a single-layer plastic high tunnel is only 1–3°F warmer than outside air temperature. During sunny days, temperatures inside can be significantly higher. The real protection comes from adding a second layer of row cover inside the tunnel directly over your crops, which traps ground heat in a pocket around the plants.
The two-layer system combines your tunnel's plastic covering with a layer of row cover draped over wire hoops inside the tunnel. Pull the row cover back during the day to let sun warm the soil, then replace it in late afternoon to trap that ground heat overnight. This approach, pioneered by Eliot Coleman, allows cold-hardy crops to survive through hard freezes without any heating.
For cold-hardy crops like spinach, kale, and lettuce, probably not. The two-layer system (tunnel plastic + interior row cover) provides adequate protection without thermal mass additions. Water barrels and other thermal mass strategies add marginal benefit but aren't necessary if you're growing appropriate cold-weather crops.
Drip tape can handle gentle curves as long as it doesn't kink sharply enough to block water flow. For beds with significant curvature, soaker hose is a better option — it's flexible enough to snake through winding layouts and emits water along its full length. Check drip tape emitter spacing as well, since wider spacing can leave gaps in coverage.
Drip tape wets a small area on the surface, but water spreads laterally and downward as it moves through the soil. The root zone several inches below the surface often has better moisture coverage than the surface suggests. Dig down a few inches near an emitter to check actual coverage before assuming the system isn't working.
For curved beds, soaker hose or gently curved drip tape can work. For complex or winding layouts, overhead micro-sprinklers provide the most uniform coverage. Farmers Friend sells overhead irrigation kits for in-tunnel use. The trade-off with overhead is wet foliage and watered pathways, so it's best for crops that tolerate moisture on their leaves.
Shop Related Products
