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
- 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.