colored Plastic Mulch?

greenman62January 27, 2014

anyone use plastic mulch ?
Heres some info since i read up on it...


Why Plastic Mulch?

Peppers responded more to silver mulch compared to black, with an average 20 percent increase in marketable fruit yield and fruit size over a three-year study. Lowest yield or marketable peppers were harvested from plants grown on either white or light blue mulch

Tomatoes responded to red mulch compared to black, with an average 12 percent increase in marketable fruit yield and fruit size over a three-year study. There appeared to be a reduction in early blight in plants grown on red.
Yellow has been shown to attract insects � but that can be a good idea. Some growers are using yellow-mulched rows to attract insects to a location where they can be killed,
Blue attracts thrips but has been very effective in greenhouse tomato production

Light reflected from red mulch has a lower red (R) to far-red (FR) ratio than normal sun-
light, while black plastic has little effect on this ratio. The lower ratio has been reported to
enhance the carbohydrate movement into the developing tomato fruit resulting in in-
creased early production. Also, many of the colored mulches, including red, are translucent
and will increase early spring soil temperature resulting in rapid plant growth, earlier
flowering, and fruit maturation.

Black mulch absorbs most ultra-violet (UV), visible, and infrared wavelengths (IR) of incoming solar radiation and re-radiates absorbed energy in the form of thermal radiation or long-wavelength infrared radiation. Much of the solar energy absorbed by black plastic mulch is lost to the atmosphere through radiation and forced convectio

clear plastic mulch absorbs little solar radiation but transmits 85% to 95%, with relative transmission depending on the thickness and degree of opacity of the polyethylene. The under surface of clear plastic mulch usually is covered with condensed water droplets. This water is transparent to incoming shortwave radiation but is opaque to outgoing longwave infrared radiation, so much of the heat lost to the atmosphere from a bare soil by infrared radiation is retained by clear plastic mulch.

in a pepper canopy, twice as much reflected photosynthetically active radiation (PAR) was measured above clear plastic mulch than above black plastic or bare soil. Although both red and black plastics raised soil temperatures similarly, higher early yields and less foliage were observed in plants grown on red plastic. Both red and black mulches reflected about the same amount of PAR, but red plastic increased the ratio of red:far-red wavelenghts (R:FR) in the reflected light.

when tomatoes are grown on red mulch they have higher yields, stronger stems and ripen earlier. Research has also found that red mulch reduces nematode damage.

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Interesting info but sources may be questionable. Most repeated trials with red mulch vs. black indicate that one might expect a small advantage in 1 of every 5 years with tomatoes. Since red mulch costs double the sq. ft. price of black very few larger scale growers are using it anymore.
I will admit that the one year that I alternated red strips with blue and black I had a lot more inquisitive customers.
I'd like to find a source for yellow plastic rolls which are almost imposible to find anymore. It was no good in the field but it is an excellent market table cover.

    Bookmark   January 27, 2014 at 9:43AM
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Hmmm. Personally I would never intentionally add plastic or anything else unnatural into a garden, especially a vegetable garden. Goes against my style of gardening naturally & organically. Why not use a natural material mulch instead? It will reserve moisture, protect soil, keep down weeds, and the bonus is it breaks down slowly to add organic matter & nutrients to the soil.

    Bookmark   January 27, 2014 at 9:44AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

In your zone 9b the use of any color plastic mulch could have some distinct drawbacks - primarily heat trapping and cooking roots.

While it works ok for some in the northern zones even though there are better alternatives, for those in warmer climates it's benefits are minimal and the risks increase.

There are many discussions about using it all over the various forums here that the search will pull up for you. And the majority of experienced tomato growers agree with bmoser's comments above - the red plastic has minimal if any benefits. It has been tested often.


    Bookmark   January 27, 2014 at 10:49AM
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Natures_Nature(5 OH)

I'm with Courtney. I garden to get away from plastic, not to be a consumer of plastic.

I never seen the benefit of plastic mulchs unless your a farm with acres trying to get the cheapest mulch. Other then price and moisture protection, what good is plastic? It doesn't decompose leaving you with rich soil, it doesn't work in harmony with the organisms in the soil, and it is just non sustainable.

I wonder about the toxins in the plastic as well. BPA free drinking bottle ok, but i doubt they make BPA plastic mulch. Or how about the other chemicals in plastic other than bpa?

Plant material for mulch is where nature is now. There's a reason she uses leaves.

    Bookmark   January 27, 2014 at 12:18PM
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The heat buildup under clear plastic will burn out roots - that's how soil is sterilized. My reading goes with bmoser above - most studies show very little difference between dark colors and black.

As a side note, I don't see the point of commenting in a thread if you don't use the product. All you do is suggest that you're some kind of superior human being - not particularly flattering to yourself. I can't imagine going into an organic gardening thread and telling people that chemical pesticides are a better choice. Just sayin.'

    Bookmark   January 27, 2014 at 2:33PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

I never seen the benefit of plastic mulchs unless your a farm with acres trying to get the cheapest mulch. Other then price and moisture protection, what good is plastic?

Weed control and moisture retention are nothing to scoff at. And using it can have some real benefits for northern gardeners when used to pre-warm the soil for earlier planting. Organic mulches don't provide that benefit. Even some southern gardeners will use it in early spring for soil warming but then we have to remove it or cover it with organic mulch once summer arrives. That would definitely be required in the OPs zone.

And it sure isn't the cheapest mulch available. So while it isn't recommended by organic gardening purists, that doesn't mean it doesn't have its uses.


    Bookmark   January 27, 2014 at 2:49PM
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i have some old black and clear tarps, it wouldnt cost me anything. that stuff is expensive
ive never burned the papaya roots with them, but i only use them in the winter for papaya. Peppers and veggies may be much more sensitive,
i will probably go with compost.
problem is i just filled a huge bin with coffee grounds from starbucks, and it will take forever to break down, theres like 50lb or more.
.i am very hesitant to add it- too fresh, as to attract the wrong bugs, gnats etc...

This post was edited by greenman62 on Mon, Jan 27, 14 at 15:42

    Bookmark   January 27, 2014 at 3:41PM
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seysonn(8a WA/HZ 1)

I have read some university study about various plastic cover (mulch). It was mentioned that RED increases tomato production by 15% -20%. Clear plastic warms up the soil better than black ( due to greenhouse effect). Black plastic radiates heat MORE at night.

I agree with Dave, using any plastic where and when you have high temps, lots of direct sun, long days .. can cause more harm than good. But places like PNW (where I am) It can have positive effect by warming up the soil early in the season. And I have plans to experiment it this year. The same study indicated that using clear plastic is better than black and it can warm up the soil by as much as 5F(vs. no plastic). That is significant (IMO) early in the season, where and when you have long and cool spring weather. Once it warms up, you can either remove the plastic or mulch over it conventionally. I would prefer to remove it.

    Bookmark   January 27, 2014 at 10:50PM
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little_minnie(zone 4a)

For larger commercial gardens and farms it is impractical to use natural mulches. Certainly they are great but when you have a lot of land to cover you can't afford that much straw. The only way I am able to garden 1/2 acre plus in MN by myself with terrible weeds around me, is to use plastic mulches for some crops. I garden in sandy soil and the plastic reduces irrigation by a ton. It also extends my season. Funny some organic gardeners are against plastic mulch but don't mind row cover, tunnels and greenhouses made of plastic and poly. I try to get the cheapest black and black/white mulch and use it as long as possible. If the drip lines under it stay operable I will leave it down and plant a different crop there in year 2. Plastic mulch is the only way I can operate my business in my conditions.

I haven't splurged on red mulch but do use the red tomato bags that Territorial sells and I love these! They work great around the tomato cages for many reasons.

I started buying the black/white mulch last season since previous summers had been so hot that brassicas were doing poorly and I just loved it last year. I had broccoli and lettuce all summer and didn't have to weed those crops like usual when I used straw mulch.

I also experimented with black plastic and potatoes this year. They did wonderfully! I have never had a potato harvest like that. Finally I can save my own seed again like I used to, saving me money! It also keeps the potatoes completely covered so no greening. I put straw on top of the plastic to sort of hill it up a little and yields were outstanding.

For me it would be impossible to grow food for 15 CSA shares and a market without plastic mulch, mostly because of weeds but also due to watering, cost and season extension. We all have to come to a level of comfort with organic principles. I rent my land and it is 3 miles away and I hate driving 6 miles a day to farm but I also do almost no tilling and discing and other things that try to make up for it. At the end of the season I can generally fit all the plastic I have to throw away into one garbage bag. I am still looking for a recycling center for drip tape and plastic mulch. The one in MN couldn't make it and closed.

    Bookmark   January 28, 2014 at 1:36PM
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We all do pick and choose our level of comfort with environmental principals... absolutely.
I am a vegetarian and in the summer+fall, home grown food accounts for about %25 of what i eat. maybe 30+ this year.
I barely generate any trash, i take my trash out once a month.
I figure a reusable tarp, or even 1/100th inch think plastic ive earned if i want to use it to generate my food. :)

I believe in being conscious about the environment, very much, but i think some people dont realize what things are the real harm and what are not.

Planting earlier from my seedling trays , especially papaya could be a real benefit to me. i plan on having at least a dozen papaya trees and up to 30-40 pepper plants plus a bunch of medicinals, guava, POMs, and other stuff.

i get like 20lb a week of grounds from starbucks, a good bit of grass clippings when summer gets here, but its not enough

    Bookmark   January 28, 2014 at 3:17PM
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seysonn(8a WA/HZ 1)

I personally don't like to use plastics as MULCH, to prevent weed or conserve moisture. Which has nothing to do with the environment. But I want to use it to combat cold and the inclement natural growing conditions. And I don't think that using plastic as cover/mulch is harmful to our environment.


This post was edited by seysonn on Thu, Jan 30, 14 at 6:37

    Bookmark   January 28, 2014 at 9:47PM
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daninthedirt(Cent TX; HZ10, Sunset z30, USDA z8a)

Interesting discussion, and the explanation of energy transport difference between clear and black much seems correct. I'm a little perplexed about the advantages of colored mulches, however. Are you saying that certain plants like some colors of light more than other colors? I'd be a little skeptical about that.

It occurs to me that light colored mulch must be an advantage in areas that get a lot of shading, and for crops that like a lot of sun. Of course, for that same reason, you get more badly sunburned standing on snow than on grass.That being the case, I have to ask. Has anyone looked into using aluminum coated mylar (e.g. space blanket) as mulch? Cheap stuff, and quite durable. It would reflect ALL the sunlight hitting the ground back up. Not very handy if you want to heat the soil, but if you want to enhance the amount of sunlight a plant gets, that would sure do it. It would also, like black much, serve for weed control.

    Bookmark   January 28, 2014 at 11:29PM
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seysonn(8a WA/HZ 1)

The color of plastic, other than clear and black, is for their reflective property not for energy transport in heat form to the soil. That is how I gathered from that study.

Black and clear plastics were studied on their effect on warming the soil. I have found that to be interestingly useful early and late in the season.

    Bookmark   January 29, 2014 at 4:55AM
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little_minnie(zone 4a)

White on black plastic keeps the soil cool.

    Bookmark   January 29, 2014 at 3:36PM
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daninthedirt(Cent TX; HZ10, Sunset z30, USDA z8a)

I understand that colored mulches are just used to reflect light of a given color, rather than to manage soil temperature. Red mulch reflects red light back upwards. I'm just a little surprised that plants like some colors of light more than others. Not clear what advantage that would give to a plant.

    Bookmark   January 29, 2014 at 3:47PM
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"Not clear what advantage that would give to a plant."

me neither.
sunlight has several colors, and even IR etc...
i am guessing the plant cells only need part of that spectrum to create chlorophyll.
POT growerrs know a lot about this, they use different olor lights

maybe if there is a lot of RED, the yellow is "blurred out" to insects, and they leave it alone?
yellow is known to attract insects...

Here is a link that might be useful: light color spectrum

    Bookmark   January 29, 2014 at 6:06PM
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seysonn(8a WA/HZ 1)

Well, they talked about mulching the ground , not making an enclosure. Obviously tomato plant will get the full spectrum as normal but with the red mulch it will get additional light near red reflection.

Black/grey plastics just have low reflectivity but no light can pass through it. So the solar heat will heat just the plastic. Then it can cool off at cold temperature and at night very quickly.

White plastic act more like a mirror, reflecting most of the solar energy.

Clear plastic will let most of the solar energy in, where it will be trapped and will heat the soil under it (greenhouse effect).

    Bookmark   January 30, 2014 at 6:51AM
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daninthedirt(Cent TX; HZ10, Sunset z30, USDA z8a)

I think that's exactly right, seysonn. But then the issue really becomes why/if plants do better with extra light of one color. In fact, for starting plants (like we're all doing now), the emphasis is on using lights that reproduce the color of sunlight. I don't see folks shining red lights on their seedlings.

Evolutionary pressure is going to make plants that are optimally adapted to sunlight. Not to red light. So there is something a bit fishy about colored mulch. Colored mulch may well have value in repelling insect pests, but ... This is the kind of thing that is easily tested -- with large, double-blind studies. References?

As I said, if you aren't worried about warming the air (black mulch) or the ground (clear mulch), but just want more sunlight on your plants, white or reflective mulch is surely the way to go.

    Bookmark   January 30, 2014 at 10:10AM
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little_minnie(zone 4a)

I don't think there is a question about IF they respond to color; university tests have shown they do. But the difference has been a bit small and maybe not worth the expense of the colored plastic.

    Bookmark   January 30, 2014 at 12:00PM
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jean001a(Portland OR 7b)

Lots of research-based info at PSU's Plasticulture site

Here is a link that might be useful: PSU's Plasticulture site

    Bookmark   January 30, 2014 at 11:24PM
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daninthedirt(Cent TX; HZ10, Sunset z30, USDA z8a)

Thanks. That's an interesting reference. That link says that colored mulches have some significant effect on insect damage, but the paper on "Colored Mulch Trial" for tomatoes it points to seems to suggest that, for tomatoes, black is a lot better than other colors for maximizing the weight of the total crop. The paper "Is there a Difference in Red Mulches", recalls an old paper saying that red mulch may provide a small advantage in tomato production, but this newer paper somewhat curiously just tested many different red mulches with canteloupes, and didn't compare red to black or none. So it really isn't clear if it's the redness that helps, or just the slightly different effect different hues had on the soil temperature.

    Bookmark   January 30, 2014 at 11:50PM
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diggity_ma(5 MA)

It's interesting how what works in one person's garden does not necessarily work in another's. I've tried plastic several times and never had satisfactory results. Don't get me wrong - I wanted to like it! I wanted it to work. Who wouldn't like the promise of less weeding, fewer pests, and increased yields? It just never seems to turn out that way for me. It had been several years since I used plastic, so I decided to try it again last year for all my warm season crops.

Here are my observations based on MY garden (yours may be different):

1) Fairly easy to install. A bit tricky to get it tucked in nice and tight around the edges of the beds as is recommended, but it only needs to be done once. Overall, less work than other mulches.

2) Difficult to control moisture! I know one of the promises of plastic mulch is that it conserves water, but I found it difficult to keep the soil moist, despite adequate rainfall AND me sticking the hose under the plastic at least once each week. I'm sure a soaker hose would work better, but our water is extremely hard and full of iron, so it would foul up a soaker hose in no time flat. So at least once per week all summer, I would turn the hose to a moderate trickle and stick it under the plastic, positioning it between plants so as not to erode the soil around the roots. Move it every 15 minutes or so, when the soil was good and damp. My hope was that capillary action would help transport water around so plants did not have to be watered individually. Unfortunately, whenever I peeled back the mulch a few days later, the result was always the same... dry, dry DRY!

3) No apparent improvement with regard to pests. In fact, squash bugs were even worse last year. Not sure if this has anything to do with the plastic, but..

4) No early ripening of fruits. In fact, tomatoes were later than ever. Then again, many gardeners in the Northeast reported this last year though, so I'm not blaming the plastic. My theory is that the heat wave we had in June sterilized the first round of blossoms, so we all had to wait until Round 2.

5) Black plastic definitely attracts snakes. This could be good or bad, depending on what variety of snakes we're talking about and how you feel about them. I saw them lounging on the plastic frequently and found numerous snake skins under the plastic at the end of the season.

I can accept the snakes (in my case all harmless garters), but not being able to control (or easily monitor) moisture was a real problem for me. Again, your mileage may vary. This is just my experience.

    Bookmark   January 31, 2014 at 10:59AM
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little_minnie(zone 4a)

I wish I had more snakes, especially those that eat gophers! For me the only drawback of plastic mulch is a gopher problem. I use drip lines in my beds (t-tape) and the plastic definitely holds in moisture. I used to use black plastic for peppers and still water with a sprinkler and found the soil stayed nice and moist under. I do poke holes where water puddles or you get stanky gross pretty fast.
As for laying the plastic- I do it by hand and have some tips. First make sure to get the soil worked nicely by tilling or by hand. Lay drip lines if using and sprinkle the area or let it rain on it. Then lay the plastic by rolling ahead of you. It makes a nice suction if the soil is wet. Then sprinkle again if you have wind problems which I do- real bad! I use both some soil on the edges and lots of blocks and rocks and staples over the drip lines. Even with all that I was having the wind take it all up if I didn't sprinkle well after laying it.

    Bookmark   January 31, 2014 at 8:18PM
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Campanula UK Z8

plenty of research on light spectrums and yields, blue white for vegetative growth, red for flowering and so on.....but this is for the leaves and not the root system. Remain sceptical about coloured plastic mulch.
regarding plastic anyway - been there done that, gave up - too much work, mess, irrigation issues and the clear-up was horrendous.

    Bookmark   February 1, 2014 at 9:48AM
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seysonn(8a WA/HZ 1)

Lets make some distinctions here about the application of plastic ground cover,

1) One application is as MULCH in true sense, for weed and moisture control . this can be incorporated best with drip irrigation line under the plastic For this application mostly black plastic is used. Then when it heats up you will need either to remove it or top it with another layer of some kind of mulch to prevent heating the soil.

2) Application to assist in trying to heat the soil in early spring. For this application CLEAR plastic is used. As the researched has shown, this method can effectively heat the soil during the day and prevent coolin/maintain heat at night.
This method and application is totally different from (1). This is a sort of micro greenhouse concept for soil that has its place in cooler climates. For example, it would have no use in the southern states zones 8 and higher.

(3) Color Spectrum application: This method is aimed at increasing production I will not get into that area.

My personal interest is in application (2) area. Living/gardening in the cool PNW, I think the use of clear plastic can be very meaningful and beneficial. And I am set to explore and experiment it this coming season.

    Bookmark   February 3, 2014 at 7:26AM
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wayne_5 zone 6a Central Indiana

I use very little plastic mulch, but here in Indiana it can have some spot usefulness. Like covering April or very early May sweet corn plantings with clear mulch until they start to emerge. Also I use a bit for some early watermelons. I like IRT100 for that and I reuse both these plastics many times.

    Bookmark   February 3, 2014 at 10:34AM
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Think about this for a second about the red mulch.

Plants are green correct? That means that the plants do not absorb the yellow through green spectrum of light, but rather reflect it. What does this leave? IR, red, blue and UV. The red light reflecting off of the mulch provides just those wavelengths (400-500nm) of light that is absorbed by the plant and utilized in photosynthesis.

    Bookmark   February 6, 2014 at 10:10PM
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daninthedirt(Cent TX; HZ10, Sunset z30, USDA z8a)

No secret that chlorophyl absorbs red and blue light. I believe that the blue light is actually used more for growth by the plants, and the red light is used more for cues about when to flower, germinate, and photo-trope (as in, lean towards the light). So you need both. I've heard that germination is largely inhibited by green light. I guess that's with seeds close to the surface. Why? Because green light is what you get when the seeds are covered by a canopy, and that's not a good time to germinate. Also, it isn't simply "red"-ness that counts. There is a big difference in plant response to "red" (600nm) and "far red" (700nm), so it isn't completely obvious what plain-Jane red mulch is going to provide best.

I still think that given all that, if a plant needs more light, the best mulch is white, because it just reflects more total light. Do that, and let the plant sort out what it wants to use. If you're in a VERY hot area, however, probably best not to increase the total amount of light.

    Bookmark   February 6, 2014 at 11:25PM
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seysonn(8a WA/HZ 1)

Plants are green correct? That means that the plants do not absorb the yellow through green spectrum of light,

Color is our perception of wave length of the light that is reflected from an object. When we see something green, it means that just that specific wave length is reflected from that object and the rest is absorbed. In other words, color doe not exist as a matter.

    Bookmark   February 7, 2014 at 3:05AM
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runswithscissors(MT 4/5)

Wow...I wish this thread existed last year.

Last summer was my "plastic mulch experiment year." I read about all those studies and wanted to find out if they would help my harvest in my garden. Here's what I discovered:

In a nutshell - they were far more trouble than they were worth. Red, green, blue and clear would work fine to heat the soil up if you had no weed-seeds whatsoever underneath. In my garden the weeds were in 7th-heaven under there and grew until they made tents out of the stuff. Black, brown, and the double black/white stuff worked much better for weed suppression. For my northern garden the dark colors actually "shaded" the soil instead of warming it up faster. But once the summer heat hit, it basically cooked everything that is still low enough to be touching (melons especially). My bare (no mulch) tomatoes did not grow any different than the ones that had red under them. (Although Wall-o-waters significantly improved vigor). I used aluminum foil in place of silver and that worked pretty well actually, and I didn't have ANY flea beetle damage on any of the plants it was under. Black/white was my favorite and I will use it for beans again this year. It suppressed weeds (black side down) but reflected light (white side up) and my beans grew really fast, healthy and did not get dirty.

One thing that is an absolute must - You must have an installed drip system underneath the plastic. I thought I could get away with not having it, by leaving bare soil strips between the rows. Not enough. The water just pools on top and then evaporates off.

Also, the colored mulches are very flimsy. Kind of like the real wimpy painter's plastic. The slightest breeze and you will need at least two people to peg it down, and then it still rips free from the pegs.

My plans for this year based on last year's experiments - Wall-o-waters for sure! Black/White under beans and melons. Aluminum foil under eggplants.

    Bookmark   February 8, 2014 at 4:02PM
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