Wall O’ Water Plant Protectors/Season Extenders – Do They Really Work?

walls of water for frost protectionDo the Wall O’ Water plant protectors really work? We live at about 5,700 ft elevation in the Inter-mountain West.

Minimum temperatures here average 40.9°F in June, 47.1°F in July and 45.8°F in August.

We’ve had at least 3 inches of snow after June 10th in two of the eight years we have lived here and had hard freezes during two other growing seasons in late June.

Our average last killing freeze is June 11 and the average first killing freeze in the fall is Sept. 8, for an 89 day average freeze-free growing season and the National Climatic Data Center gives us a 50% chance of having a frost-free (36°F) growing season of at least 63 days.

To successfully grow warm weather vegetables like tomatoes, eggplant, peppers and cantaloupe, we have to start them indoors about 6 weeks early and then transplant them outside.

Our goal each year is to transplant around Memorial Day, but we still risk losing the young plants if we don’t protect them.

In addition to our two greenhouses, we use the Wall of Water plant protector.

Walls of Water

The official name is the Wall O’ Water Season Extenders and is made in Dillon, Montana.

People in Montana can relate to our late growing season. The product is made of a heavy duty, UV resistant plastic and consists of 18 connected cells that hold water.

The wall stands about 18 inches high and covers about an 8½ inch diameter circle.

When filled with water, the Wall of Water can support itself (see note about staking). The plant inside is protected them from the cold air because the water absorbs the cold that would effect the plant and keeps the environment inside warmer.

The company makes the following claims about using the Wall of Water Season Extender:

  • Plant Earlier
  • Harvest Longer
  • Easy to Use
  • Reusable
  • Protects Plants from Cold as Low as 12° F
  • Protects Plants from Winds as Strong as 40 mph
  • Protects Plants from Animal Activity

We have used the wall of water for 10 years and recommend them highly, but are all of these claims true?

Plant Earlier – Absolutely true. We just transplanted some of our first tomatoes, eggplant and cantaloupe on May 27.

I put a min-max thermometer inside one of the wall of water to compare to outside temperatures for the first eight days after transplanting. The bottom line is the walls of water make it possible to plant earlier and helps get plants off to a faster start.

Harvest Longer – Not really. None of the plants we grow in the wall of water are harvested longer because they are in the wall of water.

The problem is, the wall of water is 18 inches tall.

How does this protect a tomato that has grown 3 – 5 feet tall by September?

In fact, a late Spring or Early Fall freeze may kill any part of the plant that is sticking out above the wall of water if additional protection is not used.

They are great for young plants, but the greenhouse effect is not helpful for any part of a plant that is taller than 18 inches and that includes ripening fruit.

Easy to Use – Yes, but when filled with water, it weighs about 20 lbs, so not everyone can easily move them around.

They are a little awkward to handle when half of the cells are full of water and the other half are empty.

We solve the problem by filling them inside a tub or bucket. Be very careful when placing them over a plant.

Reusable – Absolutely, we have used walls of water for 10 seasons.

We may have not use every single wall of water every season, so I do not know exactly how many years each one has been used, but they will last for many years.

They will start to leak. If one cell loses water, it is more likely to fall over and it is less able to protect the plants inside.

Protects Plants from cold as low as 12° F – I can’t verify 12°F, but we have had plants that survived 20°F in the wall of water.

Obviously the amount of time at these very cold temperatures matter.

If the duration of cold is short and the water does not freeze, the plants should be fine. If the duration of cold is long and the water inside the wall of water freezes, the thermal protection for the plants will be lost.

So I believe plants will be protected at 12°F for several hours, but they would not be protected for 10 or more hours.

Protects Plants from winds as strong as 40 mph – We do not trust the wall of water in high winds without additional support.

On many occasions, the wall of water has collapsed and the plant inside was damaged.

I can’t say why the Wall of Water collapsed, but now we use rebar to stake them so they can not fall over.

Protects Plants from animal activity – Since we do not trust them to stand up against the wind, we do not trust them to stand up against animals.

Perhaps it was animals that caused our walls to collapse in the first place.

The Wall of Water company claims the water can absorb about 900,000 calories to protect the plants. Is that possible?

  • The definition of a calorie is the energy required to raise the temperature of 1 gram of water by 1°C
  • so 900,000 calories could raise the temperature of 900,000 grams of water 1°C
  • or raise 1 gram of water by 900,000°C
  • If a wall of water weighs about 20 lbs when full, that equals 9.071.85 grams
  • So 900,000 divided by 9071.85 = 99.2 degrees
  • Water freezes at 0°C and boils at 100°C (sea level).
  • So technically they are telling the truth, but that assumes you are using 100°C water – do not put boiling water into the wall of water

We Recommend Wall Of Water

Bottom line, we have used them for 10 seasons now.

They have protected our plants on many occasions and help get plants off to a fast start to take advantage of our short growing season.

We have had the tops of taller plants freeze and plants have been damaged when a wall of water collapsed, but we have discovered several tips such as staking them so they do not fall and other simple things  that make them work better.

Here are our best tips for using and repairing the cells of walls of water.

– – > Wall of Water Season Extender & Ratings
– – > Wall of Water Repair Kit for Damaged Sleeves


  1. We live in the high desert where day time temperatures will soon be in the high 70s and lower 80s with night time temps dipping into the low 40s to high 30s. I am interested in using the wall o water but was curious as to how well the plants will tolerate 70 and 80 degree heat while inside the wall? Should we remove the wall during the day and replace it at night?
    Thank you

    • Hi Mandi:
      You must live in a place similar to us. Once we plant, we leave the “Wall O Water Season Extenders” up full time. At first, the small plants are completely enclosed like they were in little green houses. Within a month or so, the plants will grow above the walls o water. At that point, the walls o water help keep root temperatures constant, but the plant is the rest of the plant is exposed to the elements.

      The water temperature changes slower than the air temperature, so it keeps the plants warmer at night and on some days it will cooler inside the walls o water than the outside. When the nights are cold, we close the tops with a string. And on warm days, we open the tops so it can get warm up faster inside. When they are opened widely, the plants even get some direct sunlight.

      Temperatures in the 70s & 80s (°F) will not hurt veggies, though some plants like tomatoes will not set fruit when the temperature is above 85°F, but that should not be an issue until the tomatoes are taller than the walls o water.

      So, I set them and forget them and leave them up all season. You could remove them after your plants are sticking out the top if you wish, but if you leave the the walls o water around the plants, they will protect the roots of the plants from cool night time temperatures all season long.

      As a hint, we have had a few walls o water collapse during strong winds, so now, I always drive one or two stakes inside the walls of water to make sure they can not fall over. Otherwise, they can crush small plants. I have never had a problem when the walls o water were staked.

      I hope I have answered your question. And good luck with you plants this year.

  2. I live in Denver, similar growing conditions to yours. For several years, I have used these to plant as early as late April. I flip a standard tomato cage upside down, slip the wall o’ water over it (be careful of the pokey part of the cage – you can put wine corks on the ends) and fill with water so the cage supports it and they don’t topple. Fill it, let it warm the soil for a week or two, then lift the whole thing by the cage ends to plant your tomato. Lift it again to cover. You won’t be able to completely close the WOW this way, but I keep sheets on hand to cover if needed. I usually remove the WOW in June, once night temps are consistently over 50.

    • Thanks Cindy for sharing your tips on using the Walls O’ Water with a tomato cage. When we started having trouble with them collapsing, we ended up using two pieces of rebar (because we had lots of them already from other projects) to support the walls. Photo is on our Wall O’ Water Tips post under “Use Stakes to Support Wall O’ Water”. It’s difficult to get in enough growing days at 5,700 ft, so every extra day we can get certainly helps.

    • We use a 5 gallon bucket.

      • Lynn – I think a bucket would work fine for the night in warmer locations, but we need the Walls O’ Water for the daytime because it is simply too cold otherwise. If we only used buckets, we would never get any ripe tomatoes. It has snowed here in June!

        • Sharae Lamoreaux says

          I think what they meant was they use a 5 gallon bucket to hold the WOW while they fill it. That’s what I do and it works great.

  3. Martin Keene jr says

    Imagine how many people this has helped. I’ll have to tell my friends on the frozen tundra about this.
    Keep up the good work On helping people. I have a dream of helping people as well. I respect your work. Good job

  4. Eric Gemmell says

    The latency of the water, or heat of transformation, is given as 79.83 calories per gram. This is the amount of calories that the water must give off in order to freeze. As long as it is radiating this heat, the plant is protected. At 9071.85g times 79.83 calories/g gives 724,186.88 calories!
    900,000 – 724,186.88 = 175,813.12 remaining calories (yet unaccounted for in the product claim).
    If we divide 175,813.12 calories by the 9071.85g we get 19.38 degrees C as the change in temperature from 0 deg C.
    So as long as the initial temperature of the water is about 66.88 deg F (19.38 deg C), then the claim is justified.

  5. Many people find that walls of water leak after being used once or twice. This is true. There are 18 sleeves or tubes in each wall of water, and on an average I probably lose one tube per year per wall of water to leakage. But I have lots of walls of water that I have used for over 25 years. How do I do it? You can buy what is called a wall of water repair kit. Essentially it is a replacement plastic sleeve that you slide down inside the tube that is leaking. To make it hold water again. These repair kits can be bought at some nurseries and many places online. They generally have six replacement sleeves per package. I always keep some around and whenever I see a cell that has leaked I simply put a sleeve in to replace it. I have some of the oldest walls of water from when they were still made out of clear plastic. In some of these every single tube is now replaced with a new green plastic sleeve. But they still work and I love them.

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