Actually the Chimney effect might not be bad, especially in the cooler part of the season. Clear plastic does warm the soil, but also allows weeds to germinate.

As for what works and what doesn't, it may have to be trial and error. One would think that black mulch or clear on the ground, with one or two layers of row cover that were removed each day would be an ideal method to start with.

Jay

This was for BLACK plastic mulch. They did studies on row protection for cold with row cover and straw with row cover on top of straw. The row cover alone did better than the straw and row cover.

Plastic on top would need to be removed as soon as sun started to warm each day (depending on area), versus light weight row cover. While the light weight row cover does prevent some light from getting thru, the lighter, the more transparentcy.

Thanks for the follow-up you all.

The clear plastic mulch got the soil to 82F this afternoon with a high of only 75. The soil outside of it was 60F in the paths, and 65 in raised beds.

I went ahead and planted since it is going to cool off a bit
tomorrow and my seedlings were getting big. I covered it with agribon and home depot plastic...will have to open before going to town tomorrow.

I did another section with just the clear mulch and agribon with just a few plants.

Another thing that might be worth trying is row cover all the way to the ground over the low hoops and plastic on top of that just to about 1 foot off the ground on both sides. That way it might have a good balance of heat collecting/holding and venting? That might be something to do with your low tunnels in high tunnels. We do have an excess of sun here so the layers don't matter too much.

This post was edited by rustico_2009 on Mon, Feb 17, 14 at 21:18

there is clear plastic mulch that degrades quickly used for getting sweet corn up and running. this may be a better choice or i think it will get too hot under it when the air temps get into the upper 80's-90's. clear plastic is used to solarize the soil, kill everything in it from the heat.

It sure could get too hot, Randy.

Other options might be putting in perforated clear mulch or just poking holes or using shade cloth. I like the shade cloth idea because it leaves the full heating capacity of the clear mulch intact and would only be a few days here and there for the time frame I am talking about.

These kind of strategies are working on my seedling starting cold frames...tedious, but nothing else works.

It was 38F early this morning and the soil got down to 55 with the clear mulch, agribon 19, and 6 mil plastic...so that isn't too good.

This post was edited by rustico_2009 on Tue, Feb 18, 14 at 18:31

Update. Tomatoes I transplanted to black mulch under agribon 30 are doing good...too early to say thriving but definitely something pretty good is happening. Nothing else that was put in there is doing any good. I thought zucchini would do fine, but it looks sick though they have grown some. Peppers nothing , watermelon nothing, basil nothing...more or less predictable.

The clear mulch and agribon 19 with plastic at night, was planted just last Monday and heat is scary there but the plants are all taking save one that broke at the main stem.They have all taken to some degree. Too early to say really how well they will do.

I closed off the holes around the plants with dirt on top of the plastic around each stem and poke holes further away to fight the " furnace" effect....soil temps are great but the air between the plastic and dirt is really hot. Hope this helps. If the dirt helps, I may make up a bunch of cement collars to go around each plant thus holding the "furnace" shut. The clear just heats so much better than the black. Haven't tried peppers in there yet...it might work.

Ideally there weren't be any air between the dirt and the plastic, but I know that's hard to do. Glad your tomatoes have survived, the other stuff might perk up later. Hope so.

how do you irrigate?

Thanks, Marla, not worried about the other stuff, I would be glad to yank it and put more tomatoes when more are ready in about a week.

I'll try some peppers and zucchini on the clear..the black really doesn't get the soil nearly as hot, but does seem to be enough for tomatoes and there is the safety factor for really hot days.

Sorry missed your post , Randy, the new bed has just one row of T-tape and black plastic. The existing 48" bed with the clear plastic has 4 rows of micro tubing and the double row of plants are
between the outside row and the next row in. It's a bed that had been set up for row crops, so I just left it that way.

i was going to suggest more irrigation for your zukes and peppers and watermelons. seeing that you have the setup you are probably ahead of me with that.

Rustico, You might also put some straw on top of the plastic as the straw works as a mulch, although Marla and I were told it might hold in heat under the plastic it still decreases heat and shades somewhat when using as a cooling shade not trying to keep heat in. When I used straw on my concrete pours on top of plastic it kept the heat under or it could bring frost up so the ground underneath did not freeze. I believe that would work for plants as well.
James

Thanks James ,

I was thinking about straw as part of some strategies. It would keep the soil from getting too hot from solar gain . It could work for those winter and spring hot spells by just putting it on and raking it to the side until the hot spell passes . For later spring summer and early fall no tricks are needed. For late fall early winter tomatoes, I could plant with plastic mulch and south exposure, but since it will be way too hot for the mulch cover it with straw, then as our mild winter comes on, the straw gets raked to the side and hoops and row cover go up.

With the right varieties depending on the time of year, it seems we could get tomatoes year round. It's very close.

Valentines day transplant tomato. 4' pot for size ref. Looking pretty good. The zucchini now look good.
This is with black mulch and agribon 30. It is overcast and cool today but nice temps in there, both air and soil. Probably could have started on New Years day with same results.

The clear plastic is doing good too but those plants are behind because they were smaller transplants and were put in almost a week later.

This is the tunnel with agriborn 19 by day and plus poly at night. We are going to have a hard 50 degree rain so that might be an advantage with the poly. Other than that can't see any advantage over the agribon 30 and you don't have to vent everyday with the row cover.

Clear plastic definitely gets warmer than black. Doesent matter if it's loose. The water droplets are supposed to have something to do with how the clear is so effective. Dirt was mounded around plants to stop "furnace effect".

The jugs have water with black food coloring in it.

Looking good. Here it's still below zero nights, and 20 for highs. I know my cats are enjoying the hoop house's heat, plus they are keeping the mice out. Those mice can just freeze, IMHO.

Thanks, Marla, Got to keep the rodents down...we are about to get a cat! Supposedly a good ratter.

Our cats aren't really good mousers, but when I forget to feed them, they become some. Our cats showed up, and became 'seeing eye' cats for one old dog. We didn't realize how blind he had got until the cats started to guide him around with their tales. Bad thing, the 'free' cats were a male and a female, now we have several since we really can't catch them.

I'm not quite the 'cat lady' yet, that goodness, they seem to go visit others and stay. Other cats don't come around unless they are really gutsy.

O.K. so now We are about a month month and a half from the suggested watermelon planting dates.

Temp will not likely go below 40 and almost certainly won't have frost. Avg night is 46 avg day is 67 or so.

What do any of you think I will have to do with mulch and row cover to push water melon?

If I have my guidelines for tomatoes and get the watermelons down it's not to hard to figure out the other heat lovers. Starting 1.5 months early I could get two full crop cycles and have a nice luxury of varying maturity dates and staggered plantings. Maybe get 4-5 months of melon harvest.

i think when your watermelons blossom you have to uncover them so they get pollinated. if you want to push them you should feed them. keep irrigated well until fruit start sizing up and then let them get dry. no reason to remove covers (are these row covers or film?) until you see blossoms.

Hi, Randy, I can never do film on low tunnels, only at night and when it's raining. Well I could but with all the venting required with film, the row cover seems like a better option. I did plastic with the tomatoes on one row and uncovered it every day but plain row cover worked just as well so probably go from here on out.

So watermelon( and other crops those high heat needs) with plastic mulch and row cover.

You are right about the pollination but by that time I could rotate hoops and row cover to a new bed or put it away. We don't have cuke beetles or any other pest that bothers cucurbits.

Do you think it will work with most nights mid to high 40's and slowly increasing. Most parts of the country actually warm up faster and more at night once spring comes on.

I just planted out some claytonia transplants in my high tunnel (with a heavy row cover for additional protection). Now we are expecting a low of minus 10 degrees (F) on Saturday. I placed a thermometer under the row cover and will let you know how it goes. For the past few nights, we've been having lows of 14-16 F outside and 30 F under the cover.

Wow! Good luck, Slimy Okra. I hope it works out.

After these experiments I really don't think I need or want a high tunnel. Maybe just the frames for a shade structure wind block thing.

All the tomato plants very much need to go in cages now. They are some of the best looking plants we have grown at any time of the year. They may set more fruit because they start bloom before it gets really hot. Besides earliness this last thing could be the biggest advantage of the extra work.

I am waiting for the next trend of nights over 50 and putting them in cages and taking off the row cover and won't put them back on for the year....

We will be able to shift hoops and covers to watermelons winter squash, basil and peppers on plastic mulch or plain dirt depending on the plants, or just using them as bug protection on other crops.

This post was edited by rustico_2009 on Fri, Mar 21, 14 at 13:47

Another photo

This post was edited by rustico_2009 on Fri, Mar 21, 14 at 13:50

it looks great...i'm jealous of your climate.

It's a huge positive Randy but the trick is you really have to know how to do a little dance routine to the large temp fluctuations of any given day...I am hearing the music pretty clearly now and learning the steps.

This post was edited by rustico_2009 on Fri, Mar 21, 14 at 14:46

Friday update. The low this morning was 0 degrees F (supposed to be -5 tonight). Inside the high tunnel it was 12 degrees, and underneath the row cover a whopping 30 degrees! The claytonia is of course fine and I expect it to make it through tonight as well.

Very interesting reading.
I am not a market gardener, but I visit your forum once in a while to get some expert opinions. And I am grateful or that.

About Plastic Mulch (talking clear and black for now):

The surface characteristic of BLACK substance (anything) is to absorb(trap) the energy from the incident sun rays. Gray is similar. On that principle solar panels are painted black/gray. When you spread a sheet of BLACK plastic on the ground , it gets warm. And if it has a good contact with the ground underneath, it can heat the soil by CONDUCTION. If there is a gap, it will not heat the soil effectively.

CLEAR plastic works differently. In a way it works like glass window or panel on greenhouse etc. Contrary to the BLACK plastic , clear plastic does NOT absorb heat very much but it transmits the heat to the soil underneath(reflects some too), thus creating a GREENHOUSE EFFECT. So, it works better if there is a gap between it and the soil underneath. Just like your hoop and greenhouse is heated.
The bottom line is that CLEAR plastic is more effective in heating the soil. As some of you mentioned it is used also to SOLARIZE (that is to burn ). For this reason, I think CLEAR plastic is ONLY useful very early on when the soil temperatures are under 50F. But once the average temperature (High + Low / 2) is above 60, there is no benefit in using CLEAR plastic and perhaps it can be harmful. But you can continue using BLACK plastic much longer.

Have a good season.

I disgree that the usefulness of clear is so limited to 50 degrees soil temp. Hasn't been my experience. I have let the temps get up to 90f with tomatoes and growth has been phenomenal. At that point I had to decide whether to shade the row on hotter days or rip some holes in the plastic and this time I decided to rip some holes. The plants are shading a lot too but less since I finally suckered them,

The clear is much easier to use because no bed shaping is required. Weeds were not a disaster but I did have to reach into the holes I made in the clear and go after them. I may mulch with straw over the shredded plastic soon.

Been wondering what I would get with clear over black. Maybe throw down some chopped up bits of old hose to create a space between. I think it would provide the weed blocking with soil heat gain somewhere between black or clear on it's own, but lose soil heat more slowly at night when it is needed. I'll go ahead and try that with some watermelons where the weed blocking is more important than for tomatoes.

I use IRT plastic (which is less effective than the clear + black combo, but more convenient to use) with good results on all warm season crops.
With any kind of plastic, you have to be careful when frost threatens. Because plastic blocks the radiation of heat from bare ground, plants are more likely to freeze on marginally frosty nights in spring or fall.

What do you have going on that zucchini bed for hoops there? Can you explain? also on the top tomato pic? I can see the others are EMT.

Those little frost cover supports are things I made up before I learned what is usually used, like the 9 gauge wire which I now have a lot of, but not in the pictures, and the EMT you see.

The odd stuff, It's 3/8" rebar bent in different shapes and covered with 1/2 poly pipe scraps. Works pretty good but costs more than the more common means of supporting covers.

This post was edited by rustico_2009 on Thu, Mar 27, 14 at 21:44

One new observation, For the time of year that I planted , valentines day, it appears the heavier agribon blocks too much sunlight for at least some kinds of tomatoes and probably the peppers and basil. The romas, which I have planted before are very short, but otherwise super vibrant.

Isn't it that low light and decent temps usually make plants leggy? I think some combination of low light and something else is making them compact? Maybe light is fine but those tomatoes like more heat? Haven't gotten it figured out. The squash are somewhat compact too, and also very healthy and green plants, but yielding nicely anyway.

The lighter cloth plants are all normal for height and look great. (now uncovered and caged for the year). Unfortunately, no romas in there to compare. Seems like a no brainer just to use the lighter cloth, but this has been a mild winter so it's not proven for a more average winter.

I think short is fine as long as the plants look healthy. They're probably a little too cold at night.

I find that the heavier covers work better for me when the noon sun angle is at least 40 degrees above the horizon, so that would be late March to mid-September here. For weak winter sun, lighter covers are better.

You must be right about the cold nights, slimy okra, it bothers the romas. Solar angle is hitting 60 deg. Plus the plant is shading the black mulch now so that could be part of it.

I am posting a picture of the Thermometer in clear mulch over black that was put down on Thurs. Seems like a good idea to try to direct seed some watermelons and go to plain black for transplants when they are ready.

High air temp was 67F which is average high for this date. Clear over black might even be too hot for watermelons because we could easily get an 85 degree day. Time to shift to plain black plastic exclusively ( or the red someone mentioned), but I am going to experiment with this clear over black bed. ...maybe better for next fall/winter.

Oh Yeah, Nights are still in the mid 40's , also average low for this date.

This post was edited by rustico_2009 on Sun, Mar 30, 14 at 21:47

Photo of just black at the same time as the other photo.

no mulch at all.

Wow! You're pushing 100 degrees there! I'm jealous! Meanwhile, I was happy to see that the soil in my high tunnels was thawing every day. LOL.
I'm guessing you'll be the first at market with watermelons?

Well, The deserts not too far away probably have pretty good growth by now. Someone could bring them to market,
but I have not seen them except during mid to late summer when the stone fruit shows up.

Well wouldn't you know that if I uncovered the tomato plants and caged them up it would turn colder. The two weeks since I have done that have been the coldest since December and we had frost last night (2+ weeks after last frost date) . I didn't get the best row covered so we will se what happens....I didn't see actual frost on the plants but all over the ground and on the cars. Low was predicted to be 42 the weather service NEVER predicts our frosts.

Even without that frost, I started to realize that these plants though now thigh high, and with several sets of flowers were not going to set fruit. So, even without the frost there is my problem , probably an annual problem...all of the early work will basically be worth nothing if there is no fruit set.

None of the plants I have are known for setting fruit in cooler temps...next year I'll plant those types.

This post was edited by rustico_2009 on Thu, Apr 3, 14 at 10:31

We had a light frost 5 days ago and mid 90's today. No tomato plants have been seriously damaged. Only Peppers under ag 30 O.K.

More or less just keeping a log on this spring's experiments, but you all probably figured that out!

Uncovered a row of butternut squash we put on black plastic a few weeks ago and under agribon 30 ....they did great and are ready to lay down and run. A few transplants from the same batch of plants, in no mulch and insect barrier cover are alive, but a fraction of the size.

Well, there is brandywine fruit set on more or less the local extension's recommended time for putting tomato plants into the garden.

Of the plants put in a little after Valentines day, Almost all of the indeterminants set fruit on the first trusses despite some cold unprotected nights, light frost even. The pic is one of the brandy wines that I am removeing all suckers and lower leaves from. There are 3 or so tomatoes in there somewhere. The determinants have not set fruit yet but are good plants.

The german lunchbox will probably give the first ripe tomato other than maybe a regular cherry.

This post was edited by rustico_2009 on Tue, Apr 29, 14 at 8:27

Double row of tomatoes foreground and single just the next row over, today 9-10 weeks since transplant of 6" plants. ...some of the cages in the single row with the white pipes are set up with high hopes.

This post was edited by rustico_2009 on Tue, Apr 29, 14 at 8:21

what do you mean by a double row of tomatoes?

Sorry, the pictures were there and now they are not. I mean they are planted two rows in 4' bed rather than one row a large space then another row.

Almost 3 months since I put the tomato plants out and they are doing great but no ripe fruit yet! Determinants are just now setting tomatoes ...still smaller than Cherries!
....as usual I end up thinking..."there's a reason why people don't do this", in this case transplanting tomatoes on Valentines day... if it doesn't really save a lot of time, there's the reason.

The summer squash did produce very early and are still putting out heavily. But then summer squash aren't on the same value level as tomatoes!

I'm going to be putting out summer squash and basil in low tunnels later this week. It will be the first time I'm planting them in LTs and also the first time I'm planting them so early. I'm glad to hear you had success with them.

good luck with your squash and basil slimy okra..I did basil under row cover pretty early a few years ago and it did well...produced great all spring and summer.

I guess you have heard, 100F in lots of California and lots of brush and structure fires. 3-5 percent humidity and 50-60 MPH gusts at times.
It's almost about to cool off a little and winds are slacking off. Not good for a lot of things.