Consider the humble potato. It’s not much to look at, yet millions of people have relied on it as a significant food source for thousands of years. One only has to look at Ireland to see the importance of the potato: In 1845, when a fungus-like infestation decimated the potato crop there, nearly a million people starved, and another million were forced to emigrate to escape starvation.
Scholars believe the potato originated in the Andes Mountains of South America, and an estimated 5,000 varieties of potato now exist worldwide. Today, Asia and Europe are the world’s major potato producing regions, accounting for more than 80 percent of world production.
Most people consider potatoes a root crop since they grow underground, but they in fact grow on a modified stem underground know as a stolon. Sweet potatoes on the other hand form directly on the root of the plant as a “root tuber.” If you ever carefully pull up a potato plant when you harvest it, you will see both roots and the long stolon with a potato at the end of it. The roots of the plant will not have any potatoes on it and all those tiny potatoes you find when digging a potato are on individual stolons. There are five stages in the growth of a potato and the following table shows those stages.
In looking at this picture, does anything seem strange to you? If you noticed, these potatoes are growing under a flat ground surface and not hilled as everyone thinks is required of all potatoes. This is not the case as most potatoes grow in about the first 10 – 12 inches of soil above the seed potato. One of the reasons for hilling, especially in commercial production, is the seed potatoes are planted in a shallow trench and as the plants start to grow, the soil is “hilled up” around the leafy growth to allow room for stolon development and ease in harvesting at maturity. If you plant your potatoes deep enough, hilling is not necessary. But a reason to slightly hill your potatoes if planted shallowly is sometimes a developing tuber will break through the ground surface. When this happens, the sun shining on that tuber can turn it green which indicates the toxic chemical solanine. The solanine toxin may not kill you, but they can make a person fairly sick and can be more dangerous to small children. So the best thing to do is just throw away any green potatoes as cooking also will not destroy the solanine toxin. Potatoes are also classified into two groups: determinate and indeterminate varieties.
Determinate potatoes grow in just one layer and do not require mounding or hilling if planted deep enough. This is where people start getting confused about whether to hill potatoes or not. A lot of needless work goes on in the garden hilling determinate potatoes when it isn’t necessary. Determinate varieties are also referred to as “early season” potatoes and are generally mature in 70 to 90 days. Determinate plants also stop new growth after tuber initiation and generally produce smaller tubers than indeterminate varieties. I personally plant all my potatoes in containers and the only thing I do is cover the soil surface with a little straw mulch to help maintain moisture and protect any tubers that may break the surface and turn green. Determinate potatoes only need to be planted about six inches deep since they grow on one level. So if you try to plant a determinate variety in a “potato tower,” you are going to be very disappointed. In fact, if you try to grow any potato in a tower, you will likely be disappointed.
Indeterminate potatoes on the other hand grow on multiple layers and if not planted deep enough, may in fact need to be hilled or mounded and usually give you a better yield. Indeterminate potatoes though do not grow like indeterminate tomatoes and keep growing and growing no matter how far up you hill them as they still typically only grow in about 10” to 12” of soil. As I mentioned before, one of the reasons to hill is planting shallow and hilling to give the stolons more soil to grow in and keep them underground to prevent them from turning green. If you think about it, it’s also much easier to harvest a potato growing in a mound above the ground surface than trying to dig 10” to 12” down for your bounty. Indeterminate varieties are also considered “late season” potatoes and are typically ready for harvest after 105 days all the way up to 140 days. They also produce much larger tubers than determinate varieties. And, indeterminate varieties continue producing new growth indefinitely during their growing lifespan.
For both determinate and indeterminate spuds, the tubers generally grow above the seed potato, rarely below it. Determinates grow on one level around the seed potato and indeterminate varieties will grow above the seed potato producing stolons up the shoot to the ground surface.
So to clarify, if you plant your seed potato 2 inches under the soil surface, you need to hill a little, but if you plant them deeper and give room for tuber development, there is no need to hill your plants. I will grow determinate and indeterminate varieties in containers this year and they will do fine planted to depth with no additional soil added to the containers.
The first thing you need to do is decide which potato varieties you may be interested in and how much room you have to grow them. We have a great climate in Alaska for growing spuds as they like a lot of direct sun and cooler temperatures. At the end of this writing, I will provide a list of some of the more popular determinate and indeterminate varieties we Alaskans seem to grow.
As I mentioned before, I grow all my potatoes in containers, mostly five and 10 gallon fabric bags as they are easy to move around and are really easy to harvest. I just turn each bag out into a wheel barrow and seek out the spuds. It’s a lot easier on the back and my harvest rates are consistent with in the ground growing, of which I have done also. Moose also don’t like potato plants and the bags can be placed anywhere outside my garden proper without fear of being continually topped by those pesky but majestic creatures.
As far as your soil is concerned, be it in ground or in containers, potatoes like an acidic soil so be sure you don’t add lime prior to planting as an alkaline soil can cause scab and other problems with tuber growth. Spuds like a soil with a pH in the 5.0 to 5.5 range. Our peaty soils make that easier for us but there are additives you can use to drop the pH if necessary, like garden sulfur. They also like a good loose growing medium and soil that compacts like concrete will produce smaller tubers and wear you out harvesting them. I use about 25% sand, 25% topsoil, 25% peat, and 25% compost. This mix allows for good drainage and a less resistive soil making it easier for the tubers to grow.
Potatoes like more phosphorous and potassium than nitrogen and too much nitrogen will give you a lot of leafy growth with poor tuber production. A good 5-10-10 should work well in your ground or containers for a successful spud production. I also throw in a little wood ash to the mix for a little extra potash.
Potatoes also hate to be soaked all the time, so be sure your soils are well draining and if growing in containers or bags, be sure excess water can drain off. If we start getting too much rain and my containers are getting soaked where I think my potatoes could rot, I will pull a big piece of plastic over all the plants to let some light in but keep the excess rain out. This has always worked for me.
Most potato growers know that when their plant vines start to yellow and wilt, the potatoes are getting close to harvest time. You can actually harvest your spuds at anytime but cutting the vines and letting the tubers sit underground for 10-14 days will help harden them off and they will store longer. If they are planted in the ground and it looks like a lot of rain is on the way, you can dig them up and store in a cool dry dark place for a few weeks and that will do the same as leaving them underground. Some people wash their spuds when they harvest, some don’t, and I have done both without noticing any difference in each crop. If it looks like rain and I’ve cut all the vines from my container plants, I will cover with a tarp or plastic to keep the soil from getting soaked and rotting my crop.
I really had no intention of mentioning how to actually grow potatoes from planting to harvest as the University of Alaska Fairbanks Cooperative Extension Service has a great publication for anyone wanting to grow potatoes, especially the novice grower. The only thing I don’t like about the publication is they don’t mention the different planting styles for determinate or indeterminate potatoes, but the publication is great for describing the general process of planting potatoes.
One controversial topic between gardeners are the flowers on a potato plant. Their flowers are rather attractive and some gardeners swear that you need to pull the flowers to get larger spuds and others say no. I did both in 2020 and did not see any difference in productivity or size in the varieties I grew. I also did a little research and found several studies to determine if leaving or taking flowers off makes a difference. The study reports were fairly inconclusive and the results stated growth is more related to environmental conditions and variety grown. You decide though and if you want to remove them, do so, or leave the flowers on…it’s up to you. Imagine though trying to nip off the flowers in this field of potato plants. It may be easy for the home grower, but not feasible for commercial potato fields, and it doesn’t seem to affect their harvests.
I’d like to mention one issue before listing some common determinate and indeterminate varieties. Potato plants will develop small berries on them that look like tiny tomatoes. These are the potato true seeds and can in fact be grown into potato plants, but it is a lengthy process. The berry like fruit should be pulled off your plants and discarded if you have small children around who like to eat everything in the garden. These berries are very toxic and small hands sometimes can’t resist them, so please be careful if you have small children or grandchildren around.
Now a few popular potato varieties
(Short Season 70-90 days) (Long Season 105-140 days)
Yukon Gold Adirondack Red German Butterball Century Russet
Chieftain Adirondack Blue Russet Nugget Ranger Russet
Caribe Sierra Gold Strawberry Paw Russet Burbank
Norland Sierra Rose Alturas French Fingerling
Ratte Red Norland Green Mountain Magic Molly
Russet Norkota Canela Russet Red Pontiac
This list is by no means an exhaustive list of what you can grow in Alaska. Practically any variety can be grown here given the right growing conditions.
Have fun growing potatoes and try different varieties. Harvest at different time periods to learn how your plants grow. Competitive growers will pull their plants being careful not to break the tubers from the stolons, remove all the smaller spuds leaving the biggest tuber, and replant the entire plant with one good tuber in an effort to grow a giant competition worthy spud. The current world record potato was grown in the United Kingdom by Peter Glazebrook and it weighed in at a monstrous 11 pounds. He definitely can be categorized as a man with a passion for potatoes.
Photographs and drawings are in the public domain.