Potato towers are a hot topic, probably because a lot of people have smaller backyards and they want to produce as much food as they can. The ads are very seductive; “grow 100 pounds of potatoes in a 4 x 4 ft tower. ” And then there are the pictures of someone opening a small container and having dozens of large potatoes falling out. I never knew gardening was so easy.
There are two approaches to finding out if potato towers actually work. One is to look for actual studies that compare potato towers to other forms of growing potatoes and the other is to try and understand how potatoes grow. After all, humans have been growing them for hundreds of years so we do know something about them. I’ll take both approaches in this post.
What is a Potato Tower?
Potato plants are similar to tomatoes except that the eatable portion, the tubers, grow under ground. Traditionally, plants are grown for a few weeks, and then soil is hilled up around the plant. The tubers form in this hill which is usually about six inches high.
It stands to reason that if a small hill produces a good crop, a bigger hill will produce a bigger crop.
How do you make a bigger hill? There are several ways to do this. You can place tires around the plant as it grows and form a vertical tower. Start with one tire and plant the seed potatoes. As they grow remove leaves and place another tire around the stem. Four tires seems to be a popular height.
In the same way, you can use a wire mesh to form a cylinder. And then there is the deluxe solution where you build a square wooden structure as pictured above. Notice that the wood sides can be inserted, one above the other, as the plant gets taller. This design also makes harvesting easier.
All of these solutions are designed so that you place the starting seed tubers in the ground, and then as the plant grows, you keep adding soil to make the hill taller and taller. Add extra tires or pieces of wood to hold the soil around the plant.
At the end of the season, you have a large hill chocked full of potatoes – or at least that is the dream.
Do Potato Towers Work?
In order to answer this question we have to define what we mean by ‘working’. You will get potatoes with this system. But most people who go through the extra work of building towers want a higher yield than just doing it in the ground.
As far as I’m concerned, if potato towers do not give you a higher yield, they don’t work.
How Do Potatoes Grow?
This topic is well understood.
It all starts with seed potatoes which could be small potatoes, or larger ones that have been cut into smaller pieces. Each piece contains one or more eyes, the growing points on a potato. When the seed potatoes are covered with soil, they start making roots and shoots.
After a couple of weeks, rhizomes also start to grow. These are horizontal stems that grow for a while and then form the new potato at their ends. While this is going on the main stem is growing taller and making lots of leaves. Through photosynthesis, the leaves are making sugars which are sent down to the forming tubers.
The key to getting a lot of large tubers is to grow lots of leaves.
The description so far describes how early and mid-season varieties grow. There is one set of rhizomes which forms very near the original seed potato.
We also have late-season varieties which grow over a much longer season. These potatoes will make additional rhizomes higher on the stem; as high as one foot above the seed potato.
Potatoes are cool season crops that like cool, moist conditions when tubers are forming. Optimal tuber set takes place with a night soil temperature of around 55F (13C). When night time soil temperatures exceed 68F (20C), tuber growth is reduced, and it stops above 84F (29C).
The Height of Potato Towers
Most towers end up being three to four feet tall. The theory is that potatoes will be formed all along the stem, filling the full height of the tower. The problem is that most gardeners grow early and mid-season potatoes, which only make new potatoes at ground level.
Just because you make tall towers does not mean that the plant starts making potatoes higher up the stem, and this is exactly what people are reporting when they dismantle their towers. All of the rhizomes and potatoes are at or near ground level.
Leaves Equal Potatoes
Anyone who understands photosynthesis will see an obvious flaw in this system. In order to keep filling the tower with soil you have to remove leaves from the plant. At the end of the season you have a few leaves at the top of a very long stem that is devoid of leaves. The lack of leaves results in very little food being produced, which in turn results in few or small potatoes.
You can’t expect a lot of potatoes when you keep removing the leaves.
Too many Seed Potatoes
In normal planting, potatoes are spaced out along a row and rows are reasonably far apart. Some tower recommendations place too many seed potatoes in the tower. Such crowded conditions don’t allow plants to grow to their full potential and then don’t produce a lot of potatoes.
Potatoes Are Cool Growers
Potato towers are just large containers that have all the soil above ground. That means their soil gets hotter and drier than the same soil in the ground. Potatoes produce the most tubers when grown cool and moist. If the soil in the tower gets too hot, they stop making tubers.
Potato Towers are a Flawed Idea
The premise behind this technique is that potatoes produce tubers all along the stem. If you grow a taller stem and surround it with soil you will get a lot of potatoes. This is flawed thinking.
Early and mid-season potatoes don’t do this at all – no matter how tall the tower is. Late-season potatoes do this a bit, but only in the one foot above the seed potato. A one foot tower might help in this case, but there is no benefit to using a three to four foot tower.
What Does Science Say?
I can’t find a single scientific study that looked at potato towers.
Citizen Science Reports
If you go to YouTube you will find many videos about potato towers. Quite a few are DIY videos that show you how to build and plant the towers, but almost none of these show you the results. Then there is other type of video, by real gardeners, that show you the end result.
Admittedly, I did not find any that were very scientific, but some do have a control, usually comparing pots to towers. But if you take the aggregate of these videos you quickly realize nobody is producing a lot of potatoes using towers.
Everyone is finding all of the potatoes at the bottom of the tower, which is exactly what science predicts. I selected one of these videos and took a clip from it because Dan Rogers took the time to have a close look at the vines. This image clearly shows that roots and rhizomes are only produced at the bottom of the vine (right side of the picture), and that is where the harvested potatoes were.
Do Indeterminate Potatoes Exist?
Lots of gardening sites talk about determinate and indeterminate potatoes, but most government sites and commercial sources for seed potatoes use the terms early-season, mid-season and late-season.
If we define indeterminate in the same way as indeterminate tomatoes, where the plant keeps growing taller and making fruit along the whole stem, then I don’t think the use of the term indeterminate is appropriate for potatoes. Late-season varieties do make tubers slightly higher than the seed potato, but this does not continue along the whole stem.
It is possible that the real fruit of potatoes will form all along a tall stem that is exposed to light, as in indeterminate potatoes, but we don’t eat these fruits.
Growing Potatoes in Containers
Growing in containers might seem like the same technique, but it is significantly different. The container is simply used to provide good soil for growth. Leaves are not removed to create a tall hill, so the plant produces a good crop.
It is much easier to grow potatoes in the ground, but if you don’t have good soil, this is certainly a viable option.
- Image of potato tower made from wood, by Craftthyme; http://craftthyme.com/build-potato-boxes/
- Image of tire tower, by Tony Buser; https://www.flickr.com/photos/tbuser/2612148236
- Image of potato roots, by Dan Rogers, https://www.youtube.com/watch?v=EcCRYm4kCUs