The interior temp of my recently constructed high house is at ambient or lower when the sun goes down, or on cloudy days. How exactly does a high tunnel extend the growing season if inside temps aren't above ambient during the night. Something doesn't make sense to me. Does that daytime increase in temp help the plants that much.

I can't vouch for how it would help in your area, but where I am, in the Michigan Upper Peninsula, I can plant my tomatoes a good month earlier inside my (unheated) high tunnel, and they keep on growing for at least a month - if not more - longer than tomatoes planted in the open garden. Two extra months is a pretty big deal here

Even without an additional heat source, the covering keeps the frost off. Just a few degrees warmer plus frost protection can add meaningful extra time onto both side of the growing season. But if one wants to grow tender material through winter, the high tunnel will need heat. And if one wants to grow tropicals in there... well, that's another story- unless you live in Florida. Yes, I'm jealous of you Floridians and Gulf coast dwellers, but only in winter, and only a tiny bit!

@CaptObvious, do you have a system for heating or are you leaving it up to mother nature? And what are you planning on growing?

Hembrain said:Even without an additional heat source, the covering keeps the frost off. Just a few degrees warmer plus frost protection can add meaningful extra time onto both side of the growing season. But if one wants to grow tender material through winter, the high tunnel will need heat. And if one wants to grow tropicals in there... well, that's another story- unless you live in Florida. Yes, I'm jealous of you Floridians and Gulf coast dwellers, but only in winter, and only a tiny bit!

@CaptObvious, do you have a system for heating or are you leaving it up to mother nature? And what are you planning on growing?

Based on what I've seen on temp monitoring system over the past few cloudy days, it's cooler in the high tunnel and cold frame than outside. Nights are the same, cooler inside the tunnel than outside. Currently, at 8pm EST it's 66F insode the tunnel and 70F outside. (It is unusually warm for this time of year.)

I've been growing wiinter veggies in the cold frame, brussels, broccoli, cauliflower, and they're doing well, but we haven't had but one or two nights close to freezing. Planning summer veggies for the high tunnel, tomatoes, squash, cucumbers, etc. No heat but the sun.

Photos of each below. Just glazed in the tunnel a few days ago. Early photo of the cold frame, which now has glazing on the ends.

[url=https://www.flickr.com/gp/117800205@N05/dsL36j]



Larry

Being in zone 8a do you actually even need a high tunnel for growing in the summer?

Weedwhacker said:Being in zone 8a do you actually even need a high tunnel for growing in the summer?

From what I've read and watched, high tunnels ofer more advantages than just extending the growing season. In the summer, it's about controling the watering, protection, and more importantly in my opinion, controlling temp/sunlight so plants don't burn. Last year my tomatoes in full sun didn't do well, but late afternoon shade plants did great.

And even if I don't need it for sumer, I wanted to build one.

Larry

I can certainly understand the idea of "even if I don't need it, I want it"

One of the biggest benefits of growing my tomatoes in a high tunnel has been the lack of disease on the plants; when I was growing them out in the open, every year around the end of July or beginning August the plants would start dying from the bottom up, which progressed quite rapidly. I never did determine if it was some sort of blight, or wilt, or maybe something else (everyone around here seems to call pretty much any plant disease "blight") - but growing the plants under cover (since 2016) has totally eliminated the problem. (and the high tunnel is sitting on the same soil as where the diseased plants grew)

I can certainly vouch for less disease growing tomatoes in a high tunnel/greenhouse. I did that 2 years ago, and the plants were just about disease free.

@CaptObvious, those look like nice structures! I see your covering is opaque and that would diffuse the intensity of the sun, which is nice in summer but might be why it's cooler in there than ambient temp on cloudy days lately. The weather has been crazy, though.

Your brassica crops may be able to handle quite a chill. Where you are, I bet they may do fine all winter long.

Hembrain said:@CaptObvious, those look like nice structures! I see your covering is opaque and that would diffuse the intensity of the sun, which is nice in summer but might be why it's cooler in there than ambient temp on cloudy days lately. The weather has been crazy, though.

Your brassica crops may be able to handle quite a chill. Where you are, I bet they may do fine all winter long.

Yeah, the poly is the "clear" from Home Depot. Had to buy the 100ft roll in order to get adequate coverage for top portion of house. Further monitoring shows inside temp get 20F above ambient on sunny afternoon. I still have some sealing to do, but also planning to have a covered raised bed inside the house next winter. Saw this on "Growing a Greener World". The bed maintains plants all winter way up north. Still learning.
37F outside, 53F inside. 56F in the cold frame.

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Yup! A greenhouse within a greenhouse gives you even better temps.

how long has it been up? it can take a while for it to warm up.

I know in NY This time of year my soil is very cold, so even when I have the rare day in the 50s, the ground is still frozen..
so picture your tent like an empty cooler and the ground like a block of ice... the inside of your cooler will be, well, cool.

the higher day time temps and increasing intensity and duration of sunlight should warm the soil and once the soil temps increase it will radiate warmth at night rather than absorbing it and you should see it improve. it just takes a lot more energy to heat the soil than it does the air.