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2019 Great Potato Experiment – in Rootpouch Grow Bags

by | Jul 21, 2019 | Food, GARDENING, Soil | 2 comments

POTATO EXPERIMENT 2019: Growing ordinary food in extraordinary ways


Potatoes are easy to grow right? But when I  compare little potatoes grown commercially and little potatoes I grow myself I am shocked. Home grown are so much more flavourful and the texture is firmer and nicer. So I am looking at ways to grow more potatoes in a small area and I am surprised by the results of my potato experiments this year. 

This is not what I expected at all. I have been growing potatoes in bags, pots and the ground for years. Over time I discovered I grow better potatoes in grow bags than I do in the soil so this year I wanted to compare various materials to add to the grow bags.

When I got packaged but unlabeled potatoes from Maxine in January they were already sprouting so I left them on my counter to complete the chitting process before I used them in my great 2019 potato experiment.


I initially started growing more potatoes because Helpful Husband loves eating potatoes and they are often listed on the Dirty Dozen list (these are the twelve plants so sprayed with chemicals they are considered dirty.) Strawberries are often number 1 (one berry this year has 22 pesticides found in it!) Potatoes raised commercially are sprayed at least five times (three times in the growing season for fungus control, once in fall to kill the plants for early harvest and finally in storage to stop them from sprouting.) I am having none of that so I grow my own spuds even though soil quality in my current garden is poor.


Scab is unsightly but it doesn’t affect the flavour of potatoes. It may, however, be an indication that potatoes are low on nutrients or at least not grown in fully mineralized conditions.


I used to live in Alberta where potatoes are often scabby – possibly due to high pH or a variety or other factors I haven’t resolved yet. Now I live on Vancouver Island where soil is generally poor (mine is an almost pure white sand.) The main problem here is wireworms. These narrow orange critters drill narrow holes through my potatoes when they are grown in soil. I know it is a soil deficiency and is more common when a garden is converted from lawn to garden but the soils are so bad here it is taking years to resolve all the mineral deficiencies and I even see wireworms in newly purchased soil. I decide to my run my potato test in grow bags so I can use less soil and escape most of the problems associated with soil-grown potatoes.

These potatoes are from a garden row last year. Potatoes grown in soil in rows in the garden often suffer from wireworms. These narrow orange coloured worms normally eat grass roots but when you start a garden they have nowhere to go so they eat the potatoes. The worms leave long narrow tunnels in spuds and they are hard to store and a pain to cook. When growing in rootpouch grow bags this year I noticed all the potatoes were clean and free of wireworms.


I use the Rootpouch brand of grow bags because the people who run the company in Oregon are easy to work with and always willing to offer help and information as needed. Also, the bags are of medium quality and cost. They are considerably cheaper than the more expensive Geopots but more expensive than the super thin and floppy Smartpots. All the commercial growbag brands are better for growing than plastic or cloth grocery bags. Grocery bags just fall apart quickly and may not even make it to harvest.


Back in 2017 I harvested one of each variety all at the same time because they were growing in fabric root pouches and I wanted to do a taste test while they were fresh. This year I used a single unknown variety and compared how I grew them.


I always order organic seed potatoes from a supplier in Alberta (Eagle Creek Farms) and with shipping the cost of potatoes is high. So I save my “special”  organic potatoes for planting and eating, not experimenting. Luckily a friend gives me a bag of no-name organic yellow potatoes just before she leaves on holidays in January. These are my test spuds.

I order certified organic seed potatoes from Eagle Creek Farms in Alberta.


I have eight potatoes so I chit them on the counter for a month  and then cut them in half and plant them in 15 gallon (56 litre) Rootpouch growing bags. I have no idea if they are early, mid-season or late potatoes and I know this makes a difference but then again I am treating them all the same so the results will be valid and I will find out soon enough if they are early or late. (I discover they are late potatoes when i see the hug number of small tubers forming on stems )

Potatoes are chitted and cut in half before they are planted in late March. Notice they gradually turn green during chitting process. 


This year I decide to grow potatoes in soil plus one other item: wood chips, straw, soil or weeds. To make things equal I start with 15 gallon Rootpouch grow bags and 15 cm of freshly purchased bulk soil placed in the bottom of each bag. Purchased soil is fairly consistent and so I add the same purchased soil to each bag. I buy bulk landscaper soil, not bagged sterilized soil mix because I hope to get nutrients and biology in my purchased soil, not simply growing support. Because potatoes are heavy feeders I sprinkle a small handful of organic fertilizer on each planted pot and then add the second “test” material such as soil, wood chips, weeds or straw.


Rootpouch grow bags both new and old  are shown just before planting. These bags last for years because they are made from recycled water bottles and are rigid enough to stand up even when  they are only partially filled with soil.


I start my experiment early because I live in Canada’s warmest climate and potatoes are a cool crop. On Vancouver Island we can and do get frosts and even snow into April, but I decide I can cover my crop if need be so I start early.

I see the potatoes are sprouting early so I take them out of their plastic shop bag and set them in a shallow tray where they get light and begin to chit (sprout) naturally.

By late March, when I am ready to plant the potatoes they are nicely chitted instead of wildly sprouting.

I have volunteers coming and I wait until they arrive to plant so they can be part of the fun (Thanks Lisa and Ben!)

We cut the potatoes in half on March 28th, 2019 and leave them to dry overnight. The next morning, purchased bulk soil ( from Earthbank //fishcompost.com/) is added to each of eight bags in a 15 cm deep layer. Two potato halves are planted cut-side down into prepared bags on March 29th, 2019. A handful (1/2 cup) of Organic fertilizer (Biofert 6-2-7 from Terra-Link) is added on top. 


Volunteers in garden: Ben Redwood and Lisa Patterson help me in the garden this spring and are in charge of the great potato experiment planting.



March 28: Chitted unknown “yellow” potatoes cut in half in house.

March 29: Eight 15 gallon Rootpouch grow bags have 15 cm (6”) soil added to bottom of bags and 2 potato halves placed in each bag. Organic fertilizer (1/2 cup) sprinkled on top of soil and potatoes in each bag (Biofert 6-2-7).

March 29: Bags are topped with growing materials and labelled as follows – Yellow flag has a soil base and weed topping; purple flag has soil base and straw topping; red flag has soil base and wood chip topping and finally no flag means it is soil base and soil or compost topping (various products used including soil from old grow bags.)

Potatoes are grown in one of four materials over an initial base of soil. Here the mixed wood mulch shows what it is made of : pine needles, woody sticks and generally ground wood bits. Here you can see the potatoes as I dig in around in July after the tops wilt.


April 18: Soil/soil bag buds emerging 20 days after planting. In Soil/weed bag the weeds keep growing and I pull them.

April 23: Soil/Soil bag spuds are up 4”. Soil/woodchip bag sprouts are just emerging.

May 8: In one soil/soil bag, plants reach over the top of the bag so I add 6” more soil to both soil/soil bags. In one soil/woodchip bag plants also reach the top of the bag so I add more chips to pot. Soil/weed bag 1 is just starting to emerge and one has sprouts 8” tall. No growth on either of the soil/straw bags.

May 19: On soil/soil bag I add more soil; in soil/weed bag I added weeds; in soil/straw bag one has still not emerged so I do nothing. On soil/woodchip bags I add more woodchips. My goal is to cover the growing plants so that there is only 6″ of stem above the soil line or cover of weeds, wood chips or straw.

May into Late June: water all bags occasionally.

The early variety of potato ‘Warba’ are susceptible to scab – especially when they are grown in soil. Early potatoes produce fewer spuds overall but each one grows – if left growing in the garden – into larger potatoes.


July 15: Harvest day! Pots dry out from excessive heat and most plants are yellowing and falling over so I decide to harvest. Other pots planted later in my garden in soil or compost are still thriving because they are in areas that get watered more often so I leave those  bags as is and will harvest them later. 

I weigh the potatoes from each rootpouch as soon as I pull spuds and  rinse them. Notice how clean the potatoes are when they are grown in a rootpouch  and except for the scabs on this batch of potatoes they are perfect! If these had been grown in soil they would be dirty.


the average weight of the unknown potatoes on harvest date July 15 2019 varied with components

Trial 1

Soil/Soil Bag 1: 682 g. , 25 potatoes, very little scab on one spud only. Soil is dry to bottom
Soil/Soil Bag 2: 576 g. , 14 potatoes, 3 with scab. Soil is dry.
Soil/Soil Totals: 1258 g, 39 potatoes = average size is 32 g. but biggest was 78 g and only 4 with scab.
Notes: If I had kept them better watered and more accessible the plants would have lived longer and increased in size. Results very promising.

Trial 2
Soil/Weed Bag 1: 521 g, 10 potatoes so fewer overall, no scab
Soil/Weed Bag 2: 754 g, 23 potatoes, 3 with scab. Biggest is 82 g
Soil weed totals: 1275 g, 33 potatoes, 3 with scab; average size 38 g

Trial 3
Soil/Straw Bag 1: plant just emerging (so late but still alive!) on July 15 so left to grow and added more straw
Soil/Straw Bag 2: 570 g, 10 potatoes, 1 was 115 g so the biggest overall. No scab
Totals on July 15: 570 g, 10 potatoes, largest single spud. Average size largest at 57g

Trial 4
Soil/Woodchips Bag 1: 584 g, 20 potatoes, six had scab. Plant dead when harvested.
Soil/Woodchips Bag 2: 550 g, 25 potatoes, some very tiny, only 1 had scab
Totals on July 15: 1134, 45 potatoes, 7 with scab. Very tiny spuds ave size 25 g . I wonder if they were nutrient deficient – hence more scab?

As long as leaves are green and growing the potatoes are getting bigger in the grow bags. Once plants die back they are ready to harvest. Next year I will water experimental plants so they stay green longer and the individual potatoes size up better. I think this will change the overall results dramatically. I will also fertilize because I suspect the lack of nutrient means the potatoes in the wood mulch got scabbier.


Soil/soil 1258 g 39 potatoes 4 scab Ave size 32 g (10% of crop had scab)
Soil/weed 1275 g 33 potatoes 3 scab Ave size 38 g  (13% of crop had scab)
Soil/straw 570 g 10 potatoes 0 scab Ave size 57 g  (0% of crop had scab)
Soil/Woodchips 1134 g 45 potatoes 7 scab Ave size 25 g (15% of crop had scab)

*results from only 1 bag because one just started growing July 15 so there will be more data at end of summer. Maybe too much light affected sprouting?

Heaviest overall Yield:  soil/weed bag

Largest number of potatoes: soil/woodchip bag

Biggest single potato: soil/straw bag

Scabbiest potatoes: soil/woodchip

Most of the root pouch grown potatoes are clean as they are harvested. Very few overall had scab or even dirt clinging to the spuds.



The cleanest (scab-free) potatoes grow in straw and the next best were in  the soil I purchases. I know different soils and varieties of potatoes are  affected differently by scab.

The biggest potatoes grow in straw but the light  affected the growth and one bag did not emerge until early July from a late March planting. (Use more straw or bury potatoes in soil before I top them with straw in future)

The smallest potatoes were in wood chips but if these were watered and fertilized I may have had twice the yield because the number of potatoes harvested was largest – they were just small.

Corle, our truffle dog, loves the smell of soil and is very interested when I pile up the harvest from the 2019 Potato experiment. In all we harvested just over 4 kg (just over 8 pounds) from the eight root pouches. In the future, if I water more, we could double or triple that harvest.


1. Put all spuds on an auto watering (micro-irrigation) system so each bag is watered daily. The soil was dry in all the bags on day of harvest and the plants died back early because they dried out.  Potatoes will size up better if they get more water (just imagine the ultimate size of my 45 soil/woodchip spuds if they are watered more.)

2. Bury potatoes instead of setting them on top of base soil level. This way the effect of light will not be holding the straw trial back from sprouting (soil/soil bag was up first probably due to dark while soil/straw bag has delayed sprouting.)

3. Fertilize all potato bags monthly with a tablespoon of Biofert 6-2-7 so they all have equal access to nutrients on an ongoing basis. This might reduce scab in low fertility pots (wood chips.)

4. The soil/straw potatoes are largest overall at 57 grams  each on average and the biggest potato came from the soil/straw bag at 115 g which is 4.5 times bigger than the potatoes grown in mixed wood chips. Imagine the results if I use more straw and bury potatoes first? Ah, next year.

5. None of the samples in root pouches had wireworms while most of the potatoes I grow in soil in my garden do have wireworms.

6. Average size serving Helpful Husband (HH) likes is 215 g and my desired serving size is 115 g. With a harvest of 4237 this means 20 servings for HH  or 37 servings for me. (average 30 servings from 8 bags barely watered.)

7. Total harvest was 4237 g. Most materials were free but grow bags cost $15 each so total cost in first year was $120.00 or on average $4 per serving. Luckily bags last several years because they are made from recycled plastic water bottles.


Straw used is not organic. It is just a bale from a neighbour because he uses three bales annually in his Christmas Creche scene. Straw was still quite fresh and had not started breaking down when I used it. In the future I may use partially decomposed straw. NOTE: I stopped growing straw bale gardens years ago when the price of straw went over 10 dollars a bale. (they were $5.00 each when I first started buying them about six years ago.)

Wood chips were mixed and had been sitting since last fall in the elements so some decomposition had started. I think this could be the easiest material to obtain free so I will try it again but with more fertilizer and water.

Soil is expensive to buy. I use it this time because I need some for other projects. I do not suggest digging soil from your own garden or buying sterile sol mix (in bags)  because if you use your own soil you may get wire worms in bags. The cost of bagged soils far exceeds bulk and results don’t warrant the extra expense (potato yield was average but size per spud was second smallest.) I do suggest  using natural (bulk) soil over bagged because the flavour of the potatoes was amazing compared to any I have ever purchased and that flavour comes from the soil.

Weeds. Easy to find in my garden and the results are promising. I suggest this is because the overall nutrient content of weeds is higher than the other materials. Once I am fertilizing more I will see if there is still a benefit to weeds.

Re-using soil? I plan to reuse the soil after this first year. I will also add some to my compost pile and use it directly in the next bags planted. I suggest pushing the spuds down deep into the soil used at the base of the bags to make sure they get dark and start growing up into bag.

All potatoes turned out to be mid to late season so they formed potatoes along the stem as they grew. We did not know this initially. Also, all the other grow bags in my garden are still green and growing so they are getting more evenly watered while I am up working in garden. Adding irrigation to the trial spuds will help them grow bigger and better in the future.

If you want to try growing spuds in pots, bags or soil with a cover of a free material such as weeds or wood chips give it a try but I think the overall benefit of the grow bags is the way they breathe  so the microorganisms always have air. Also, the plants, roots and microbes are never  waterlogged or overly soggy. This means they never smell. Give it a try!

PS I keep planting in grow bags as I harvest the earliest crops. Last year my last crop went into a bag on August 6th but this year I ran out of “seed” potatoes on July 15 right after I replanted the experimental plot.  I am able to do this because I chit all my potatoes early and leave them trays ready to plant. I also have a BC greenhouse so I can plant a late crop indoors!


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 Donna Balzer is the Brand Ambassador for BCGreenhouse Builders and she has two greenhouses in her big backyard.

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  1. Tell me more. How does it work? What is the science behind it do you think? Is it available anywhere outside of Calgary?

  2. Zeolite works wonders for lessening scab on potatoes.

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