Questions on: Potatoes

Ron Smith, Horticulturist, NDSU Extension Service


Q: I'm doing a project on phytophthora infestations in potatoes. Do you know what the chemical equation is for the mold to occur? I know the fungus thrives in 75 percent to 100 percent humidity and needs mild temperatures. I need to know the chemical equation of how this occurs in potatoes on the molecular level. Also, do you know what happens if someone eats the fungus? There has to be a reason why not to eat infected potatoes because a lot of people starved to death in Ireland. (e-mail reference)

A: Thanks for your question! I'm forwarding it to our undeniable NDSU potato expert at all levels (breeding to cooking), Susie Thompson. She will get back to you with a solid answer that should get you an "A" on your project. I'm glad to see your interest in this subject. Have you read "Famine on the Wind?” It was one of my favorite readings when I was taking a plant pathology course in college. It is out of print, but I'm sure your school or public library would have a copy. Reading it could help flesh out your project with some good background information.

The following is an answer supplied to the reader by Susie Thompson.

A: Thank you for the question and having an interest in potatoes. I am unaware of a chemical equation relating to the infection or invasion of potatoes by phytophthora. Let me tell you a little about the Irish potato famine and the newer strains of late-blight. The Irish potato famine happened because the potatoes rotted, often right in the field. Additionally, the foliage (plant canopy) would have been impacted first. Therefore, the tubers may not have formed because of the vine’s premature death. At that time in history, many Irish peasants lived on potatoes and milk supplemented with other foods, but these staples provided all the necessary amino acids for human health. Also, some of the harvested tubers may have broken down (rotted) while in storage, again reducing the food supply. To my knowledge, there is no toxin produced by late- blight fungus that would cause harm to humans. That is not the case with some other crop pathogens, such as headblight in wheat that produces an aflotoxin or ergot in many small grains. The genotypes of the late-blight fungus changed between the 1840s and the early 1990s, when late-blight again reared its ugly head. The new biotypes are much more aggressive and virulent, attack different parts of the canopy and rapidly grow on tubers and foliage, even at high temperatures. In foliage, the optimum temperature is 59 to 68 degrees, but it can grow at
much higher temperatures. For example, temperatures into the 80s under high humidity (75 percent to 100 percent). The optimal temperature for hyphal growth and development in tubers is 50 degrees. The lower limit for growth has not been determined. The base temperature of this obligate parasite may be related to that for potato leaf and sprout development, which is 39 degrees. I hope this helps some. A good article was in the Valley Potato Grower magazine about 20 years ago (sometime between 1985 and 1989, if I recall). It was written by Phil Nolte and may have been in two parts. Best wishes on your project.


Q: I have a question about my potatoes. I have one plant with three small "fruits" the size of cherry tomatoes. What are they? (e-mail reference)

A: These are the potato fruits. Potatoes, tomatoes, peppers and eggplant are in the same family. The fruit is not edible, so don't eat it. The fruit will not interfere with tuber development under the soil.


Q: I have a way to control potato bugs. As soon as the potatoes start coming up, I plant a few marigolds here and there around the potato plants. I haven’t had any bugs for three years. (Binford, N.D.)

A: Thank you for writing! I'm glad this technique works well for you. My success has been inconsistent, although I keep trying!


Q: A year ago, I helped scrub 75 pounds of potatoes for a pancake feed. I washed the splatter from my glasses, but not immediately from my cheeks. They became quite red. With time, the redness has reduced, but not gone away. I’ve tried to learn what potatoes are washed in before marketing (everyone says just water) or what chemical is used to fertilize potatoes. Thank you for any advice. (Waseca, Minn.)

A: There is nothing on a potato skin that would cause this sort of reaction. I suspect that it may have come from the cleaning agent in the wash water. In either instance, the reaction should not have lasted this long. Surely, a dermatologist can provide something that will give you relief.


Q: I have been told not to put potatoes in my crisper to keep them from sprouting before I get them all used. Why is this not OK? (e-mail reference)

A: Because the temperature in the vegetable crisper is low enough to convert the starches in the potatoes to sugars, making them sweet tasting. Keeping the potatoes dark and cool (at about 50 degrees) will do a good job of keeping them from sprouting.


Q: I am wondering about storing potatoes. My wife said she read that potatoes and apples should be stored together to inhibit sprouts from forming on the potatoes. She also read that they should not be stored together. Any thoughts on the issue? She is hoping to store them in a cool cellar. (e-mail reference)

A: Store potatoes away from apples and pears because these fruits release ethylene, which hastens sprouting. Potatoes may rot faster when stored with onions, but that is because onions store well at warmer temperatures than potatoes.


Q: Someone called my office and said his potatoes were blooming like crazy, but was told to cut off the blooms. Does that sound right to you? (e-mail reference)

A: You get the best tubers if you leave the blossoms. Flowering does not take away from the quality of the tuber. In fact, leaving the blossoms on actually contributes to quality, according to Susan Thompson, our NDSU potato specialist.


Q: Is there a herbicide treatment that can be used on potatoes in small plots to control weeds? (e-mail reference)

A: About the only thing I can suggest is “strawing” the potato pieces. The seed pieces are placed on the soil surface and covered with 4 to 6 inches of straw. The sprouts should emerge through the straw and weed growth should be inhibited. Add more straw as the season progresses and the plants continue to grow. This will keep the tubers cooler, the soil moister, control weed growth and be easy to harvest. The straw is pulled away carefully and the tubers harvested right from the soil surface. This is an organic method of weed control and produces (usually!) prize winning potato tubers.


Q: My son has to bring a potato to school that has sprouts on it. Is there a quick way to make this process happen? (e-mail reference)

A: About the quickest way is to find a neighbor who grows potatoes in his garden to see if he has any that are sprouting. Most potatoes sold in supermarkets have been treated with growth inhibitors, such as maleic hydrazide, around harvest time to prevent sprouting. Organic growers would not use such chemicals, so you might try locating an outlet that specializes in organic produce to see if it has any. I’m willing to bet the teacher who gave this assignment does not know about sprout inhibitors.


Q: I need some information about the green on potatoes. I've seen green on potatoes before, but nothing like it was last year. My husband and I planted white potatoes last spring. When they were harvested last fall, almost all had green on them. The small ones were green all the way through. When I peeled the other ones, I tried to get all of the green peeled off. Even then, while cooking, green showed up on them and the water was slightly green too. (Ellendale, N.D.)

A: The green is a chlorophyll formation from exposure to light. If they came in from the field green, that means they were not covered with enough soil to prevent light penetration. The green coloration also means there is a toxin accumulation. If taken in small amounts, it can cause a mild digestive upset. It can be toxic if digested in large amounts (whatever that would be). The white potato is really a modified stem, hence it's ability to carry on photosynthesis and turn green. It takes very little light reaching the tuber to stimulate chlorophyll production. Any potatoes that show anything more than a very superficial green coloring, should be thrown away.


Q: Why do potatoes turn green? (Tioga, N.D.)

A: Potatoes turn green because light reaches them. The soil covering must be porous enough for this to happen. You should not eat green potatoes.


Q: We have two garden plots and both have severe problems with blight. Potatoes are most affected though the tomatoes, beans and cucumbers have been hampered as well. We rotate what we plant, buy new seed and clean off old plants regularly. I sprayed the potatoes three times with fungicide but they were still greatly affected. Would leaving one plot idle next year and working it as a fallow help? Would it be helpful to plant a cover crop such as rye? (Tappen, N.D.)

A: Going fallow or with a rye cover for a year would help. So would three-year rotations away from anything in the tomato or potato family.


Q: We have a problem with our potatoes. They were planted in the garden for the second year in a row. They did not come to a full bloom, looked sickly and were treated for fungus. They did look better but did not grow much and quickly dried up before the season was over and before they could mature. Can this fungus be in the soil and infect the next crop? (Beulah, N.D.)

A: Always start with clean, certified seed potatoes, and rotate the planting site with something outside the potato family such as peas, beans, corn, or cabbage. Only plant potatoes in the same site every three to four years.


Q: A lady planted russetts, norland and kinnebec spuds this past spring. She has lots of vines but very few tubers. My guess was too much nitrogen but she says no fertilizer, compost or other material has been added to her garden for years. We had lots of rain early then nothing but hot and dry weather for the past eight weeks. (LaMoure, N.D.)

A: In a word, drought. Potatoes need moisture to develop decent tubers and without it nothing but pips develop. Being shallow rooted, they are sensitive to a lack of moisture in the upper soil profile. When that is coupled with 100-plus degree days like we had last month, you won’t get much in the form of tuber development. Being a member of the nightshade family, the vines will thrive in the heat, and it will take more than the drought we had to kill them.


Q: Potato bugs have eaten most of the leaves on my potato plants. I have them under control now but will I still get potatoes from these plants? (E-mail reference)

A: Yes, but probably only small ones.


Q: I am having a problem with my potato plants. They are turning yellow at the base. They are just starting to go into the blooming stage. The plants were doing fine up to this point but I did notice the plants were not growing in height the past couple of weeks. They are a lot shorter than my neighbor’s. (Hosmer, S.D.)

A: The problem could be late blight, which is caused by the fungus Phytophthora infestans. This is a disease that is often activated from tubers that have come from storage and were previously infected. The disease favors high moisture and moderate temperatures. Rain, dew, sprinkler irrigation and even high humidity can trigger spore development. Use good cultural practices to control the disease. Rotate the crop away from anything in the family such as tomatoes, peppers, eggplant and, of course, other potatoes. You should do that for at least three years. Plants that don’t have enough nutrients or have other stress problems will be more susceptible to this fungus or the early blight fungus (Alternaria solani). Chemicals, at this point, may or may not work and the effort and expense may not pay off because the outbreak has started. Materials like Bravo, Acrobat, Mancozeb, or others may provide some help. Next year be sure to begin with disease free tubers.


Q: We heard or read there is a product that you can incorporate into the soil to control Colorado potato beetle. Is there such a product? Spraying is a labor intensive project and, in a large plot, time consuming. Also, what is Bt? (Ashley, N.D.)

A: Bt-bred potatoes are a thing of the past, thanks to the near maniacal hysteria over genetically bred food crops. They worked beautifully when we planted the Bt-enhanced potatoes next to the non-Bt potatoes. It was as if a wall existed between the two plantings. At first Bt potatoes were taken off the consumer market because they never really gained much of a market share. When the hue and cry reached a fever pitch, they were removed completely from any source - consumer, commercial, or research. Now we are back to the near stone age method of spraying or picking off beetles by hand. Bt or Dipel are the materials that you can now purchase to apply on the potatoes. They have the same effect as the bred-in material did, except that you must apply it repeatedly, every 10-14 days, to get control. They are safe for warm-blooded animals and environmentally friendly. Bt (Bacillus thuringiensis) is a naturally occurring bacterial disease of insects. Dipel as well as Bt, are the manufactured forms of this active ingredient. These materials are also very effective against leaf and needle chewing caterpillars and certain beetles. These products can be safely used on essentially all food crops.


Q: Every year we end up with a lot of potato bugs on our potato plants. Is there anything we can add to the soil before planting and cultivating? (Edgeley, N.D.)

A: The best procedure is to not plant potatoes or any other member of the family such as eggplant, pepper or tomatoes in the same location. Next, see if you can get Bt enhanced potato seeds to plant. This is a biological control agent that is bred into potatoes and has proven to be quite resistant to the Colorado potato beetle.


Q: There was something on TV about planting potatoes in a garbage can. Supposedly you could then grow potatoes inside during the winter. Do you have any information on that? (Cando, N.D.)

A: I doubt that you could generate enough light indoors to seriously "produce" potatoes. You might get a semblance of a vine to grow under lights or in a sunny window, but I doubt that it could be pulled off in a garbage can. Isn't it amazing the questions that get thrown at us?


Q: I thought you might have an answer to this question. The potatoes on the vine are approximately two inches long and one inch wide. There are approximately 15 potatoes on the plant. (E-mail reference)

A: Wrong cultivar for the region or the weather was such that it did not encourage turberization until late.


Q: For three years, I have planted potatoes in three different spots. Each time they grow well but are all covered with warts. We like new spuds with skins on, but I can't bring myself to serve them without peeling. Is something lacking in our soil? This is all new ground that we acquired by tilling up part of the lawn. (Tower City, N.D.)

A: It sounds like you are being plagued by potato scab, an organism that is found in the soil and causes one of the most serious diseases of potato. I suggest trying some of the resistant cultivars such as Goldrush, Katahdin, Kennebec, Red Norland, Red Pontiac, Russet Norkotah, or Superior, which is a white potato.


Q: I have a question concerning potato plants that are very tall and lush with lots of blossoms but few potatoes. Idaho red potatoes were planted in late May. They are now 3 to 3 1/2 feet tall and in full bloom. After digging 12 hills, there were only three to four small potatoes found. Is there a way to force a potato's energy into growing the potato instead of the plant itself? (Dickinson, N.D.)

A: It sounds like the plants have had too generous an application of nitrogen-containing fertilizer. Accept what comes this year, and try not to be so generous next year.


Q: We have a very unusual problem with our potatoes. We planted certified Pontiac reds. We like to harvest them when they are small. I dug up one plant a few weeks ago to make room for a new rhubarb plant I was given and there were two small white potatoes I didn't think too much about it until I dug up four more plants a few days ago. They are also white. I asked our county agent here and he didn't know what to think of it. They taste good . Also, some of our Ponderosa pines are turning brown beginning at the tip of branch (new growth). Some of the trees are young and some are older ones. (Dickinson, N.D.)

A: I am far from being a potato expert, but it could be that a sport or mutation has reverted back to the original form. That's the only possible answer I can come up with. Enjoy them anyway! Usually tip browning or burn in pines is an indication of backfill over the roots, salt accumulation in the plant tissue, or simply environmental stress. Take your pick -- at this point your guess is as good as mine.


Q: My potatoes are not blooming. Will they still produce any tubers? (Linton, N.D.)

A: They should, but that depends on the cultivar you are growing.


Q: How do I fight existing tomato and potato blight? What can I do to prevent it? (Breckenridge, M.N.)

A: If it is just getting started, carefully pick off the infected leaves and dispose of them. Then, try to keep the water from splashing onto the foliage when watering. This can be accomplished with a soaker hose, drip irrigation, and/or generous mulch around the plants. If it is widespread, then fungicides need be applied. There are plenty of "garden" fungicides for you to select from at the local nursery or garden supply store. Finally, select those cultivars that are resistant to the diseases, and try to rotate the plantings with something that is not in the same family as the potato and tomato for about three years.


Q: I believe that our potatoes last year suffered from blight. They were growing well when I noticed a few spot on the leaves. Following a rain, they lay flat and died. We did get some potatoes, although not the usual amount, and the flavor, especially of the skin, was not good. They didn’t keep well either. Is it blight? Can it be treated when it is first seen? We had planted new Norland seed 4 to 6 feet from where we had grown potatoes before. (Pierre, S.D.)

A: You need desperately to practice crop rotation with anything but members of the potato family, like tomatoes, eggplant, and peppers. Potatoes and their family members should stay out of the same site for a minimum of three years. This is the first and most important step in disease control.


Q: I planted a sweet potato in a flower pot. It has sprouted out all over the place and is growing fast. How do I plant it in the garden and where do the tubers grow? Also, can you stop an evergreen from growing up, up, up? (Jud, N.D.)

A: You really jumped the gun on starting the sweet potato this early! If you can keep it alive, plant the whole thing when the danger of frost is over. They will develop their tubers along the root system over the summer. In the future, simply plant the appropriate cultivar directly into the garden. I cannot accurately advise you on your evergreen question. There are pines, spruces, junipers, arborvitaes, firs, and cedars to name a few. I don’t want to give you a generic answer like "prune it" without knowing which species it is, as the timing and technique differs for each.


Q: I read an article about a way to stop potatoes from sprouting in storage. The answer was to put dried lavender, sage and rosemary in with the potatoes. Where can I purchase lavender? How much of each herb is needed? (E-mail reference)

A: Lavender should be available where you can find the other two herbs, which can be found at Sandie Shores, Herb's Herbs & Such, in Rochester, MN, phone (507) 753-3081, e-mail Mitakuye@aol.com . Everything is grown organically. As far as the amount of each goes, none of my references tell me exactly what that would be. I would assume a generous distribution to keep the volatile oils noticeable in the potato bin.


Q. Last summer some of my potatoes (Kennebec) were rotten in the ground and would also rot in the bag after digging. Can you help me with these two problems?

I really enjoy reading your articles and your answers are very helpful. (Platte, S.D.)

A. Concerning the potato rot: I checked with our potato breeder, Dr. Jim Lorenzen, and he thinks the problem is late blight, a fungus affectionately known as Phytophthora infestans. This fungus thrives when the temperatures range from 50 to 75 F and the relative humidity remains around 75 percent for at least 48 hours. Late blight symptoms will show up in two to three weeks. The fungal spores reach the tubers, and cause the rot to continue after the harvest.

If it gives you any small comfort, this is a famous fungus, the same one that caused the great Irish potato famine, and that contributed to the loss by the German army during World War I.

To control: Rotate crops and spray with chlorothalonil when the plants are about 6 inches tall, and repeat every 10 days. Allow the tubers to cure about a week before digging.


Q. This is in response to the reader who asked about sweet potatoes. A good variety to grow is the Georgia Jet. I start my plants in the house after Christmas, but I would not advise planting them outside until early June. I think you should try planting them again, and I am thinking about trying it commercially. (Fullerton, N.D.)

A. Good hearing from you. Yes, I'll give them a try again to satisfy my own craving for them. Let me know if you try them commercially. Wouldn't it be a kick to have N.D. producing Yankee Sweet Potatoes? Thanks for writing.


Q. Following is information for the reader who had some questions about sweet potatoes. Planting instructions: About one week before planting, mound soil in a row, cover this with black plastic and secure the edges down. Plant out the plants after danger of frost. When planting, cut a slash in the plastic and plant about 18 inches apart. Water the plants when planting and again a couple times in the following days.

You can now ignore them until frost, when it is time to dig them. They need to be laid to dry and cure in the sun and warm temperatures, so I usually dig mine around Sept. 12. When digging, be careful of skinning them as they keep better when they are blemish free.

Before frost, I cut a couple lengths of foliage and plant them in the house. I thus have a nice plant in the house for the winter, and I cut the plant up in the spring and root the pieces in moist soil to plant out again. A tuber that is sprouting can also be put in moist soil to produce cuttings. All the sweet potatoes need are sun and some 80 days. I have grown some that weigh over 3 pounds. (Berlin, N.D.)

A. Wow! Thank you for such good, detailed information about sweet potatoes. I think the largest sweet potato I grew was more like 3 ounces, not 3 pounds.

So, yes, I'll try them again, as the ones purchased in the store just don't measure up. Thanks for writing.


Q: What would you recommend as the best red, white and russet potatoes for storage? (E-mail reference, Bottineau, N.D.)

A: Here is a list of the potatoes that are good for storage: 

'All-Blue', blue -purple skin and flesh, late; 

'Caribe', bluish-purple skin, white flesh, early; '

Carola' buff skin, yellow flesh, late; 'Norgold M', russet skin, white flesh, early; 

'Norland', light red skin, white flesh, early; 

'Pontiac' (also known as ‘Red Pontiac’, red skin, white flesh early; 'Russet Burbank', russet skin, white flesh, midseason; 

'Yellow Finn', yellow skin, dark yellow flesh, mid to late season; 

'Yukon Gold', yellow skin, yellow flesh, early to midseason.


Q: We had a potato patch of some six varieties which yielded quite well, considering the drought we had. One variety, Russet Burbank, yielded well, except 90 percent of the tubers were all connected in the most grotesque and interesting shapes. Some were two or three nice-sized potatoes with many small ones attached. Is that normal for that variety? Second, one day our bush beans looked nice and healthy and I had a good picking. The next day I noticed many tiny black insects. We sprayed with Sevin, but then the plants turned yellow and died. I find others had the same problem. A neighbor planted later for a fall crop and had no difficulty.

A: I suspect the dry (and probably hot) weather had something to do with both problems. Potatoes do best where 1 to 1 1/2 inch of water is applied each week, there is ample sunshine, and the temperatures are not high. Variations in moisture and temperature can cause strange things to happen. It is unusual for Sevin to cause the reaction you describe. I suspect some residue of herbicide may have been in the container you used. If not that, then something that was a petroleum base was in the container.


Q: Many of the potatoes from our garden were greenish under the skin last year, and I was concerned that they were not good to eat. I would like to know the cause of this greenishness. (Bowdon, N.D., e-mail)

A: The cause of potatoes turning green is light interacting with the epidermal tissue, which causes chlorophyll to form. Irish potatoes are really underground stems, and when exposed to light for any length of time, the spuds will turn green. That green color causes a bitterness in the potatoes, and possible stomach upset, and too much green potato consumption can cause poisoning. They will lose their green if they are returned to total darkness for five to seven days and will be OK to eat afterward. If when peeling the potatoes for cooking some green should show up, simply peel it away to the white and everything will be OK.


Q: My onions are starting to sprout. Can I use the sprouts just like you would green onions? Are potato sprouts poisonous? Can you eat them like any other type of sprout? (Stanley, N.D., e-mail)

A: Yes, the onion sprouts will be OK, but you can't eat the potato sprouts.


Q: I grow potatoes in my garden, and they are such a pretty plant, I have one growing in the house. It's only 2 weeks old and is 6 inches tall. I'd like to see if I can get it to produce. Will the blossoms need to be fanned to pollinate them? (e-mail)

A: Potato plants in the house? Now I've heard it all! You can fan them or simply give them some gentle shaking when (if!) they flower. Unless you plan to harvest the fruits of the potato and sow the seed inside, there is little objective in attempting to get them to set fruit. Keep in mind that these fruits are not edible, and their setting is not a prerequisite for the tubers to develop.


Q: Last year I received a free packet of seeds labeled "Solanum guineese; Garden Huckleberry." The plants are beautiful with huge, dime-sized fruit that I would like to make jelly out of. My neighbor told me they were poison and a noxious weed. Is this true? Also, can a weed in the nightshade family cross-breed and make huckleberries poison? (Carrington, N.D.)

A: Tell your neighbor that potatoes are poisonous if they are green, but not if they aren't green. The same is true of garden huckleberries. Unripe, they are poisonous, but when ripe, they are not. They will not spread like weeds unless you allow the fruit to drop; they are annuals and will be killed with a hard frost. There's nothing to worry about concerning cross breeding.


Q: I have a problem with blight in my garden, on the tomatoes and potatoes. Is there anything I can do to get it out of the soil? I've been told to cover the garden with clear plastic and the sun will destroy it. Is this true? (Detroit Lakes, Minn.)

A: Oh, if only it were that easy! The best thing you can do are all of the following:

Be fanatical about cleaning up the garden debris this fall.  Rotate the crops--have beans, corn, carrots, or cabbage follow your tomatoes and potatoes.   Select resistant cultivars.  Employ drip irrigation, or at least avoid watering overhead.  Monitor regularly for diseases getting started. At first symptoms, apply a multipurpose fungicide. 


Q: We've just harvested out potatoes and have a very small yield. The plants had a blight and died prematurely. What can we do to have better results next year? We planted three varieties, and the Red Norland were best. Are some kinds more resistant? Is there a spray that will control the disease? (Tappen, N.D.)

A: Potatoes are best grown on land that is part of at least a 3- to 4-year rotation: beans, cabbage, corn, potatoes etc. There are resistant varieties or cultivars to consider as well, and Red Norland is one of them. Others are Goldrush, Katahidin, Kennebec, Red Pontiac, Russet Norkotah and Superior.

Concerning sprays, I cannot advise you unless I know what did the killing. There is verticillium, fusarium, several potato viruses, black leg, scab, early blight and late blight. Using resistant varieties is the best approach. Red Norland and Kennebec (white) offer the broadest range of disease resistance.


Q: In the past few years there have been little green berries that look like tomatoes in clusters on the top of my potato plants. What causes these berries, and what are they called? Also, if I bring in my tuberous begonia this fall will it continue to bloom or does it need to rest? And finally, is it beneficial to give peonies bone meal in the fall, or do you recommend waiting until spring? (Tuttle, N.D.)

A: Those berries at the top of the potato plant are actually the fruit of the potato--but non-edible so don't eat any. Yes, your tuberous begonia can give you many more weeks of blooming beauty. Bring it in. And bone meal applied in the fall would be available to the peony by next spring.


Q: We used certified seed for our potatoes, and we hadn't planted any potatoes for five years. They are scabby with only one or two to a vine. What is wrong? I placed marigolds around my garden because I was told that they would get rid of bugs, but the bugs ate them all up, only leaving the stems. (Jamestown, N.D.)

A: Wow -- you do need help!

The scab on your potatoes is soil borne, and once the potatoes have it, there is nothing you can do. The best defense against this is to get cultivars that are known to be resistant to the disease. Some examples are Goldrush, Katahdin, Kennebec, Red Norland, Red Pontiac, Russet Norkotah and Superior.

You probably had the "nice" marigolds--deodorized hybrids. Next time try the stinky old-fashioned kind, they usually work better. 


Q: I have heard about planting potatoes in a barrel and I am looking for more information on it. I would like to know how and when to do it. Have you had any experience with it? (Carrington, N.D.)

A: I have had no direct experience with growing potatoes this way, but I have known people who have, and swear by it. I'd suggest making sure the barrel is free-draining. Then, plant the potatoes in sandy loam around Mother's Day weekend. As the vine grows, add more soil and when fall frosts arrive, begin your harvest. 

Never bury the vine completely, always leaving a small portion exposed to the light. Be sure also that the barrel is placed in direct sunlight for maximum growth. 


Q: Can you tell me why my potatoes are growing in bunches joined together? They look really weird and I would like to know what is causing this. (Pierre, S.D.)

A: The problem could be one of two things: a varietal trait or stress-caused physiological disorder caused by heat or drought. Russet Burbank is one of the more sensitive to problems, so I recommend Goldrush or Russet Norkotah. They both will provide uniform baking potatoes.


Q: Can you tell me what causes scabby potatoes and what to do to solve the problem? (Lehr, N.D.)

A: This is a soilborne disease organism that develops from perpetual cropping of potatoes. I suggest a three-year rotation, and planting with resistant cultivars like Russet Norkotah, Red Pontiac, Norland or Superior.


Q. When I plant flowers in containers the soil becomes so hard the water runs right through and out the drain holes. The plants are not getting the water that they need. Also, last summer some of my potatoes (Kennebec) were rotten in the ground and would also rot in the bag after digging. Can you help me with these two problems?

I really enjoy reading your articles and your answers are very helpful. (Platte, S.D.)

A. If you add copious amounts of sphagnum Canadian peat moss to the container mix, I guarantee that it will hold water much better than it ever has.

Concerning the potato rot: I checked with our potato breeder, Dr. Jim Lorenzen, and he thinks the problem is late blight, a fungus affectionately known as Phytophthora infestans. This fungus thrives when the temperatures range from 50 to 75 F and the relative humidity remains around 75 percent for at least 48 hours. Late blight symptoms will show up in two to three weeks. The fungal spores reach the tubers, and cause the rot to continue after the harvest.

If it gives you any small comfort, this is a famous fungus, the same one that caused the great Irish potato famine, and that contributed to the loss by the German army during World War I.

To control: Rotate crops and spray with chlorothalonil when the plants are about 6 inches tall, and repeat every 10 days. Allow the tubers to cure about a week before digging.


Q. Enclosed please find a small consignment of potatoes I grew in my garden. They are a variety called Carole and the seed stock is sold by a seed company in Maine, Pinetree Garden Seeds. It is a medium-sized, yellow-fleshed potato and a German import. I have been raising this variety for several years now, and it appears to do well if provided sufficient moisture. The flavor is real good, especially if fried. However, none of the seed catalogues in this area (the Midwest) ever list it and nobody seems to know anything about it. So, I am sending you a sample so that you may try them out (i.e. eat them) and, if you wish, give me your evaluation. In any case, you have provided me and others with such useful information that it is now time that somebody gave you something. So, Merry Christmas and I hope to hear from you in the future. (Beulah, N.D.)

A. Wow—thanks! It was good to receive something that wasn't rotting or covered with insects! You bet the Smith family will enjoy them—probably for a special dinner.


Q. I am having problems with my potato crop. The leaves are being eaten up. I powder with Garden Dust, but it doesn't help. (Oakes, N.D.)

A. Your potatoes are likely being devastated by the Colorado potato beetle and a disease known as early blight.

Follow a spray schedule of Sevin alternated with pyrethrin every seven days or until infestation is diminished.

To control the blight, spray with a fungicide containing chlorothalonil, repeating weekly until foliage dies naturally. Next year, begin spraying as soon as the spuds are six inches out of the ground.


Q: I am having quite a bit of trouble with blight in my tomatoes and potatoes. Will the addition of copper to the soil help with the problem? I know of people in
Williston that do apply copper and it seems to help. What do you think? (Amidon, N.D., e-mail)

A: Perception is everything, and if the copper seems to work, then so be it. But don't over do it, or plant toxicity will be the result. Copper IS a
micro-nutrient, meaning that very little is needed for the effect desired--20 parts per million max. I would rather you apply the needed copper (and
other micro-nutrients) through the use of a product like Miracid or something similar. That will reduce greatly the chance for toxicity.


Q: Can you tell me a natural way to stop potatoes from sprouting in storage? (E-mail reference)

A: My September 1995 copy of Organic Gardening, page 42, states, "Try putting some dried lavender, sage and rosemary in with your potatoes when storing them in a cool place. Researchers have found that oils in these herbs suppress sprouting and inhibit the growth of bacteria that can cause potatoes to rot in storage."


Back to Vegetables/Fruits Menu
Back to the Hortiscope Table of Contents