Higher Yields Growing Potato in Growing Bags
Perhaps you have found this web page because you are researching growing alternatives for your small garden, or you already are growing potato in containers and you want to increase your yields!

You found the best web page to answer your questions.

People make claims about growing boat loads of potato in containers, and I can ensure you that what you are reading here are the results of an on-going professional research for the benefit of the gardeners' community.

This research is done as part of Kenosha Potato Project, and you are invited to join the Project Facebook page to network with hundreds of Potato Gardeners.

Watch this YouTube documentary

Many thanks to Jeff Baas, a professional videographer, who donated his time to document the Kenosha Potato Project in the summer of 2012. And thanks to Barb Leable for providing this VIDEO TRANSCRIPT ... so you can read while you watch the video and better understand what I'm saying ;+).

See for yourself what I learned about growing potato during a season of extreme drought, without access to water for irrigation. The video runs for a full hour, starting in June and ending with the harvesting of late varieties in October.

About half way [31 min] I show you seed berries of the variety Dheera. Seed berries produce potato botanical seed [aka TPS]. Growing potato from seed produces new tuber varieties.

YouTube Documentary

More Interesting Links
2012 the worst year ever - record setting extreme drought in SE Wisconsin

2012 has been my worst year ever! I've planted almost 2,000 small potato tubers in over 300 growing bags. Thank God this Project is not a business as I would be out of business now!

A farmer would plant a 2 oz. seed piece and hope to harvest 2 - 5 pounds per hill. That is a crop yield of 16 to 40 times ... some heritage potato varieties are called Fortyfold and Quarantina [forty times in Italian].

The 2012 yield vs planting weight is probably equal to Negative 20% because I have harvested about 20% less than what I have planted. This result is so bad that one should really think hard if investing in container growth of potato is a smart choice.


The worst year teaches great lessons

On this web page I'm sharing with you the mistakes that I've made and I plan to show you how to get a good return on the investment.

It pays to use; High Quality Growing Bags [1], Selected Potato Varieties [2], the Optimal Growing Soil Mixture [3] and the Best Growing Method [4]. Short cuts may lead to poor results and a waste of your time.


[1] High Quality Potato Growing Bags

I have been using Potato Growing Bags for many years; starting in 2008 with a few black bags made by www.gardeners.com - then in 2011 I've tested colored bags, first red then tan, to compare how lighter bag colors keep the soil mixture temps lower. At higher temps potato vines will neither produce tubers, nor bulk [increase tuber size].

Starting 2012 I'm also testing taller bags [18" vs. 14"] to prove if it is possible to grow more tubers higher in the bag. Higher crop yields should be achieved with optimal seed crowding of tuber varieties which structure stolons at different levels [see 2].

Some of my bags have been used for 5 years and I trust they will be used for an other 5 years or more. It pays to invest in high quality bags just for the longer life.

The porous fabric of the www.gardeners.com Potato Growing Bags aerates roots, prevents heat build-up and allows excess water to drain away. The 18" size is perfect. Bags should be bunched together in groups of at least 4 in order to reduce the area exposed to drying winds.

Dehydration is the biggest problem I've faced. See the best growing method [4] for more tips in preventing soil mixture dehydration.


[2] Selected Potato Varieties

My involvement with Seed Savers Exchange and the US Potato Genebank has led to building a rather large collection of potato varieties. I've found that growing my collection in gardeners.com Potato Growing Bags is the most convenient method for these reasons:

  • Each variety is contained in one "tagged" bag [no risk of confusing varieties].
  • 20 bags fit in the same garden area that would be needed for a 15 ft. traditional row - in a 15ft traditional row I could only grow 5 varieties with proper spacing.
  • Potato vines grown in bags usually produce smaller tubers - better for my seed potato needs.

Year after year I accumulate data on which varieties work best grown in bags.

These are the most important variety features:

  • Tolerance to higher soil temperatures
  • Tolerance to irregular soil mixture moisture
  • Tuber setting and bulking at higher soil mixture temperature
  • Tendency to develop serial tuber setting on longer stolons


This picture shows a long stolon with a "topical" tuber set at the end, one "pea sized" tuber set a little lower - attached to the stolon stem, and one more on a side branch.

Perhaps this is an other benefit of using gardeners.com Growing Bags as one could better analyze the stolon structure, and how tubers have set while harvesting.

Obviously the next step is to optimize tuber bulking! Lots of tuber setting without consequent bulking, growing its size, seems a futile exercise.

Counter clockwise below I'm showing a stolon with a root system looking like hair - notice there are no roots between the small tubers on top of the bag soil mixture and the "hair-like roots above". This will be further explained in point 5 of my Best Growing Method.

But most importantly we now need to focus on variety selection. I'm making a wild assumption here by guessing that most varietal selections have been done in the last 200 years for the benefit of the farmers - not the gardeners!


In the picture with my pink pen [14 cm = 5.5"] placed at the bottom of the vine stem along a web of stolons reaching as far as 15 inches away.

The stolon length is contained by the bag but you could imagine stolons growing many feet for some varieties [like the perennial variety Papa Chonca].

This stolon web belongs to the var. Morada Ojuda. In 2012 this bag has produced over 140 tubers; a hundred in micro size and more than 40 in mini size [chestnut size and larger].

You can find extensive information on many Heritage Varieties [including the perennial variety Papa Chonca which has survived many Wisconsin winters in my garden and now grows like a weed] in my Potato Collection Catalog.

Which varieties work best grown in bags?

I don't know yet, because in two consecutive years I've not found confirming results.

Here are a few varieties which are looking good:

  • Calrose - in normal 2011 conditions has grown larger tubers, and 2012 looked good
  • Charlotte - in normal 2011 conditions has grown 15 standard size vs. only 7 mini/micro tubers
  • Kenya Baraka - in extreme drought 2012, no watering conditions, has grown mostly larger tubers [2 small, 20 mini vs only 7 micro] showing high tolerance to drought and heat, as could be expected from an African variety.
  • Morada Ojuda - in 2012 has produced over 140 tubers [none larger than a walnut]
  • Rattviks Rod - in normal 2011 conditions has grown a huge amount of tubers [109]
  • Russian Banana - in normal 2011 conditions a KPP Members reported over 8 pounds harvest
  • Sarpo Mira - in extreme drought 2012, no watering conditions, has grown largest spuds
  • Up to Date - in extreme drought 2012, no watering conditions, has grown regular size tubers, and zero micro tubers


If you don't like the taste or texture, why grow it!

Another aspect of this research is to define the taste of Heritage Potato.

New in 2012 we have started a partnership with the US Potato Genebank to work on taste evaluations. Are you interested in becoming a "Potato Sommelier - a Potato Taste Expert?"

We are also interested in building a catalog of Potato Recipes linked to very specific potato varieties. And any article which describes the nutritional value of potato.

Here are two examples of what we would like to accomplish.

  • Let's say you like potato salads, and the Norwegian Potato Salad with fish appeals to your taste ... why not grow a potato variety which may be the best for that recipe? We are suggesting Eila Korvu's Finnish potato for this specific purpose.
  • In time we would like to add a taste description to all the potato varieties of our catalog, and here is an example for the variety Blue Victor - We tasted it and found it a little flaky, tending to be waxy, sweet and earthy. The skin is very thin.

Once you have opened the Variety Catalog, just search for the words "We tasted" to see which varieties have already been rated for taste.


[3] Optimal Growing Soil Mixture

The goal here is to retain maximum moisture and provide optimal nourishment to the vine and tubers. Rich compost is probably the best choice as it is proven to retain 7 times more moisture than poor field soil.

I'm always looking for additional ingredients to add into the mixture. So far I have tested several different ingredients but I don't have conclusive results on cost vs results ratio. The list includes:

  • Coconut coir [a mix of coco chips and coco peat]
  • Dry leaves
  • Sand
  • Shredded paper
  • Straw
  • Wood chips and shavings [sold as animal bedding]
  • Worm castings

What have I done wrong so far? Don't repeat my mistakes!

More specific details will be offered later for my Best Growing Method [4], but for now I want to recap what I have tried and has NOT worked.

Growing Bag manufacturers suggest to put a layer of soil in the bottom of the bag, place the seed pieces in the bag, cover them with a few inches of soil, and keep adding soil as the vines grow.

It has been proven that potato seed pieces are subject to dehydration if covered with just 2" of soil. Best results are obtained in traditional agriculture with seed pieces planted at 6 to 8" depth.

Healthy vines will easily grow through 12 to 14" of soil! Therefore I believe it is best to cover the seed pieces with at least 6-8" of soil immediately at planting time. More details will be offered later for My Best Growing Method [4].

Another BIG MISTAKE I've made is the use of straw. Straw doesn't provide any nutrition to the vines, nor works well to retain moisture. Straw is a cheap bag filler, and so is shredded paper. A total waste of your time.

Coco Coir tested during the extreme drought season of 2012 may be a good consideration for further testing in the future.

Animal bedding wood shavings worked very well as a top cover. Worked well to shade surface tubers, as well as a weed suppressant.


[4] Best Growing Method

The final goal of this research is to determine the best planting method, for the optimal potato varieties, followed by the correct cultivation that leads to the highest yields.

This Section needs to be diveded into these parts;

  1. General challenges
  2. Seed piece selection and preparation
  3. Soil mixture in the bag bottom layer
  4. Seed piece placement in the bag
  5. Bag filling and covering
  6. Bag layout and placement in the garden
  7. Cultivation and irrigation
  8. Harvesting

[1] General challenges

These are the major challenges for growing potato vines in a container:

  • Lack of a deep root system
  • Soil mixture dehydration
  • Soil mixture temperature

A solution to the first challenge could be to use a container with an open bottom. Obviouly gardeners.com Potato Growing Bags don't offer a solution to this challenge. We believe that this is the greatest challenge to growing large tubers in bags.

Monitoring soil moisture is critical for healthy vine growth and tuber bulking. In my garden I don't have irrigation, and certainly I don't have the time to water 300+ bags. Watering is paramount for a high crop yield. In 2013 I'plan on watering a selected number of bags for yield comparison.

Soil mixture temperature may be kept lower in colored bags vs black. Fabric containers for sure keep the soil mixture temperature lower than in plastic containers. Plastic containers are probably the worst choice.

Not to mention used car tires! That choice is beyond BAD! Car tires release terrible compounds in the soil mix. Food for your thoughts: - Would you cut a piece of tire and chew it as gum? Growing potato in tires is almost as gross and disgusting!


[2] Seed piece selection and preparation

During the extreme drought season of 2012 most seed pieces planted have dryed up before emerging. Clearly I recognized how the seed piece is responsible for the initial strength of the vine while the root system is not established yet.

In conventional farming it is usual to cut seed potato into 2 oz. pieces. This practice has two main purposes; first it multiplies the seed pieces, and it ensures the seed piece will decay over time. At harvest time whole tubers planted as seed may be confused with the new potato crop in machine harvesting. I DO NOT recommend this practice for gardeners, especially when you grow potato in bags you need the full strength of whole tubers as seed piece.

Gardeners are not too concerned about confusing the old potato "seed piece" with the new ones. Usually it is very easy to tell which potato was planted in the spring. Often it shows cracks, clear discoloration, and it will easily break if squeezed.

I have planted small tubers whole. I select mini tubers the size of a chestnut, up to a small peach. These selected tubers need to be prepared for green sprouting 2-6 weeks before the date of last expected hard freeze.


- For how long could a seed piece be "green-sprouted?"

Many months! This picture shows an experiment of a small tuber left on my windowsill for many months [October - April]. Over 6 months the tuber has turned green and grown a very short, fat sprout.

I use egg cartons to place the seed tubers under growing lights. The egg carton keeps the tuber in the desired direction.

You will notice how sprouting is stronger from the "sprouting end" - opposite the "stern end", borrowing a maritime term. Often the stern end shows in the skin the spot where the stolon connected the tuber to the potato vine.

At planting time the tubers will be placed in the soil in the same direction and produce stronger vine emergence.

If you think about it - this seems so logical - yet I bet you have never planted a fingerling correctly. I have always placed them flat in the soil (horizontally) until I've recognized what I'm reporting here. Fingerlings should be planted VERTICALLY, like the oblong shaped "Christmas Island Red" which is seen in the front row of the picture above.


[3] Soil mixture in the bag bottom layer

The lack of a deep root system is clearly the biggest drawback when growing potato vines in bags. Therefore the quality of the soil mixture in the bag bottom is paramount for both vine nutrition and moisture retention.

I have been experimenting different soil mixtures. So far best results are obtained with compost mixed with worm castings and coconut coir. Coconut coir is a sustainable natural fiber which shows great moisture retention.


[4] Seed piece placement in the bag

As I have suggested above - see green sprouting - the tuber should be placed into the bottom layer soil mixture with the sprouting end facing upward.

The extreme drought season of 2012 has clearly demonstrated that tuber pieces placed away from the bag center may dry up and die off. In the past I would place 6 pieces in the bag; one in the center and 5 in a star shape around it.

Starting in 2013 I will only plant 3 seed pieces per bag. Placement will form a triangle with each tuber spaced about 3" apart in the bag center - about 7" away from the side of the bag. The side of the gardeners.com Potato Growing Bags is made of porous fabric designed to aerates roots, but at the same time the soil mixture is bound to dehydrate and eventually dry up, if it doesn't rain or you miss to water.


[5] Bag filling and covering

Once the seed tubers are correctly placed in the bag, I fill the bag immediately with more compost almost completely. Don't wait for vine emergence.

In 2012 I have experimented with less compost and straw to create a layer of "shading material" for tubers to grow in. BIG MISTAKE - as you can see in the vine picture at the top of this page.

I've suggested that growing potato vines in bags allows for a more accurate analysis of stolon and root system structure. The picture above which I'm refering to shows a hair-like root system which has developed into the wood shavings layer placed on top of the straw.

In the 2012 experiment I could recognize that potato vines DO NOT develop root systems in straw, but they do in wood shavings. Most importantly I discovered that small tubers developed higher on the vines where a root system grew in the wood shavings.

Wood shavings are used to create a 1" layer on top of the compost. This layer works as a moisture barrier and prevents weed seed sprouting. Plus it offers the benefit of quickly recognizing when anything other the potato vines is emerging.

In this picture you see a small red tuber trapped in the frozen layer of wood shavings during my last harvesting day on November 18, 2012.

The 1" thick wood shaving formed a frozen lid over the compost which kept moist and NOT frozen.


[6] Bag layout and placing in the garden

I organize bags in double lines of 10 bags to counter act the loss of moisture from the bag sides. If you only own 4 bags and bunch them together, at least half of the bag is protected by the other bags and will have less exposure to drying winds.


[7] Cultivation and irrigation

Possibly the biggest benefit of growing potato vines in bags is the very light need of cultivation. There may be very little weed sprouting which is quickly removed before the potato vines canopy grows large enough to shade anything else.

The only chance to produce higher yields is with irrigation or regular watering. If you leave the bags to the chance of occasional rain falls, you must accept very low crop yields.


[8] Harvesting

I wait to harvest until the vines have dried up completely. I believe that the energy of the vines transfers to the tubers, thus providing the tubers with more energy to survive the winter dormancy.

Bags are really easy to harvest. It takes me a little longer because I always like to analyze the stolon and root system structure of any variety to recognize which varieties grow best in bags.

The bag content is first dumped in a wheel barrow to shift for micro tubers, then the soil mixture goes in the garden to grow vegetables and flowers.


Page updated: November, 2012

Wanted: Potato Gardeners

If you'd like to participate with the Kenosha Potato Project - here are your options:

  • If you live in Southeastern Wisconsin - please email me at seedsaver@curzio.com
  • If you live somewhere else in the USA or Canada - are you a member of Seed Saver Exchange? We have a few gardener who participate with the Kenosha Potato Project within the Seed Saver Exchange.
  • We have members of our Global Potato Network in Europe and are always please to cooperate with any gardener / farmer. Sending seed abroad is restricted or difficult ... but we may find ways to cooperate.

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