By: Kristi Waterworth
Growing potatoes is fraught with mystery and surprises, especially for the beginning gardener. Even when your potato crop comes out of the ground looking perfect, the tubers can have internal defects that make them appear to be diseased. Hollow heart in potatoes is a common problem caused by alternating periods of slow and fast growth. Read on to learn more about hollow heart disease in potatoes.
Although many people refer to hollow heart as a disease of potato, there is no infectious agent involved; this problem is purely environmental. You probably won’t be able to tell the potatoes with hollow heart from the perfect potatoes until you cut into them, but at that point it will be obvious. Hollow heart in potatoes manifests as an irregularly-shaped crater in the potato’s heart — this empty area may have a brown discoloration, but that isn’t always the case.
When environmental conditions fluctuate rapidly during potato tuber development, hollow heart is a risk. Stressors like inconsistent watering, large fertilizer applications or highly variable soil temperatures increase the likelihood that hollow heart will develop. It’s believed that rapid recovery from stress during tuber initiation or bulking rips the heart out of the potato tuber, causing the crater inside to form.
Depending on your local conditions, hollow heart can be difficult to prevent, but following a consistent watering schedule, applying a deep layer of mulch to your plants and dividing fertilizer into several small applications can help protect your potatoes. Stress is the number one cause of potato hollow heart, so make sure that your potatoes are getting everything they need from the get go.
Planting potatoes too early may play a part in hollow heart. If hollow heart plagues your garden, waiting until the soil has reached 60 F. (16 C.) may help prevent sudden growth. A layer of black plastic can be used to warm the soil artificially if your growing season is short and potatoes must go out early. Also, planting larger seed pieces that haven’t been significantly aged seems to be protective against hollow heart due to an increased number of stems per seed piece.
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Q: I have a question about the potatoes that we grew in our family garden. This year some of our russets and Red Pontiacs have bad spots in the middle of the potatoes. Not all tubers have the problem, but we've had to throw some that were totally unusable. What causes this, and what can we do to prevent it in the future? - Paul Meyer, Fargo.
A: The disorder is called 'hollow heart,' and affected tubers have voids or cracks in the middle, which are sometimes brown and discolored. When I was with North Dakota State University, we used to joke that hollow heart was a good thing in russet baking potatoes because the voids gave a spot to hold the butter and sour cream.
Some of our garden potatoes also have hollow heart this year. We've cut open very nice potatoes, only to find the center is ruined. The outside of the tuber usually shows no symptoms. Potatoes with hollow heart are safe to eat, and damage can be cut away if enough of the tuber is left.
Instead of being caused by disease or insects, hollow heart is called a physiological problem. According to university extension services, the exact combination of causes isn't completely understood, but it happens through interactions of weather, air and soil temperature, soil moisture, cultivar, plant spacing and available nutrients. Hollow heart seems to be worse when a period of rain follows a dry spell.
Tubers might react to the sudden moisture increase by a quick spurt of growth, which cracks the center open, similar to the cracking that happens in tomatoes and carrots when rain follows dryness. Commercial potato growers minimize hollow heart risk by carefully monitoring soil moisture and fertility.
To avoid hollow heart, maintain even soil moisture, avoiding fluctuations. Mulching with straw or grass clippings can help.
Q: I know maples often do poorly in heavy clay soil. Is there another tree with nice fall color that might be better adapted? - R. Larsen, Grand Forks.
A: Prairie Torch Buckeye, developed by NDSU, and Autumn Splendor Buckeye, developed by University of Minnesota, both have great fall color: orange-red with golden tones. These varieties of buckeye become full-sized shade trees and are better adapted to soil types throughout North Dakota and Minnesota. A fascinating brand-new buckeye from NDSU is called Lavaburst, which, I hope, will be available in the near future.
Q: The stems of my African violet leaves get soft and rot where the stems touch the rim of the clay pot. Is there a way to prevent this? - April Felton, Alexandria, Minn.
A: Clay pots are ideal for most houseplants, but the juicy stems of African violets are sensitive to the minerals that tend to accumulate on the rim of clay pots. Many violet growers choose plastic or ceramic pots instead, or coat the rim of clay pots with aluminum foil or dip them in canning paraffin.
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by Katrina A. Zavislan, Dr. David G. Holm, and Robin Young* * (10/18)
Purple majesty potatoes were developed by Colorado State University. Photo by David Holm.
Potatoes are in interesting crop that can be successfully grown in Colorado home gardens. The potato, or Solanum tuberosum, is in the plant family Solanaceae. It is related to peppers, tomatoes, and eggplants, but is adapted to higher elevations and therefore harsher growing conditions. Native to the Andes region of South America, they were brought to Europe and later North America. Potatoes are a good source of vitamin C, potassium, vitamin B6, and fiber, and are naturally fat free.
Potatoes vary in shape, size, skin color, and flesh color. Some common types are russets, reds, whites, and specialties (including fingerling) potatoes. Gardeners should choose a variety based on the length of the growing season, disease pressure, garden size, and desired use. A few popular potatoes developed by Colorado State University include:
|Canela Russet||Russet||Baking||Medium||Long term storage potential|
|Colorado Rose||Red Skin||Boiling||Medium||Good red skin color retention|
|Mercury Russet||Russet||Baking, frying||Very early||Suitable for short growing seasons|
|Purple Majesty||Specialty||Roasting, sautéing||Early||Purple pigments are antioxidants|
|Red Luna||Specialty||Boiling||Medium||High yield|
|Yukon Gold*||Specialty||Boiling, roasting||Medium||Attractive yellow flesh|
*Yukon Gold is not a CSU variety, but is very popular with home gardeners
Potatoes in the grocery store are typically treated with a sprout inhibitor and will not grow if planted in a garden. It is best to buy certified seed each spring that is inspected and within acceptable limits for diseases. Garden centers, reputable, garden catalogs, or your local CSU Extension Agent are all sources of certified seed.
Prior to seed preparation for planting, the potatoes should be kept between 50 and 65 Fahrenheit and away from direct sunlight for up to two weeks before planting to encourage germination and growth. However, in areas with short growing season, gardeners may use green sprouting to encourage early growth. To do this, arrange the potatoes in a single layer in a dry area exposed to light, such as a kitchen counter. When sprouts appear on part of the potato, turn it over to encourage even growth. The tubers should be planted before the sprouts reach one inch long.
Tubers, or part of potato tubers, are called seed pieces when they are planted in the soil. Each seed piece should have at least two eyes, as the stems will emerge from the eyes and grow into mature plants. If possible, plant small potatoes that are about one to two inches in diameter. These seed pieces do not need to be cut. The small tubers will not have a wound from cutting, and will therefore have no risk of disease transfer from a knife or of the cut site drying out. Potatoes smaller than 1 inch in diameter should not be used as seed, as they have limited stored nutrients available resulting in slower growth. Larger potatoes can be cut into two to three ounce pieces in preparation for planting. Best practices include:
Cut seed potato pieces can be planted immediately if the soil temperature is 55F or above. Alternately, the seed pieces can be kept in a dark humid room for four to seven days before planting. This will encourage a callus, or scar tissue to form, protecting the cut site from diseases in soil.
Gardeners should identify a spot in their garden with well-drained soil and no low spots where standing watering can pool to plant their garden. Potatoes grow best in sandy loam soil, but gardeners can manage a wide variety of soil types. Sandy soils can dry out quickly and may need more frequent watering. Soil that is high in clay can produce misshapen potatoes and should be tilled to break up large clumps prior to planting. Adding finished compost can provide organic matter and nutrients to the soil. However, both fresh manure and grass clippings can have weed seeds or too much salt. Additionally, manure may have been exposed to herbicides that can damage vegetable plants.
To apply the correct amount of fertilizer and manage the soil appropriately, gardeners should test their soil to determine pH, organic matter, and nitrogen levels. This can be done at the CSU Soil, Water, and Plant Testing Lab by bringing in a gallon size bag ¾ full of dry soil for testing.
Understanding the soil characteristics of a new garden space allows the gardener to select the appropriate type and amount of fertilizer. Potatoes grow best in a soil with a pH between 5.0 and 6.0. If a soil test is not available, gardeners can apply a fertilizer with a balanced ratio of nitrogen, phosphorous, and potassium (N:P:K) such as 10-10-10. Following is a typical fertilization strategy:
|Before planting||1 lb. fertilizer per 10 row feet||Mix or rototill into top foot of soil|
|1 week after emergence||.5 lb. fertilizer per 10 row feet||Band 2 inches away from the plant, water after fertilizing|
|4 to 6 weeks after emergence||.5 lb. fertilizer per 10 row feet||Band 2 inches away from the plant, water after fertilizing|
It is important to rotate crop families about every three years to maintain healthy soil. If potatoes are planted in the same place for several years, pathogens can thrive in the soil and easily infect the next potato crop. Most pests and diseases can damage plants in the same botanical family, but cannot harm unrelated crops. The legume family, including beans and peas, is a good choice for crop rotation due to its ability to build nitrogen in the soil, while potatoes can deplete the soil nitrogen.
Potatoes can be planted up to two weeks before the last killing frost. The soil temperature should be at least 55F during the day and 45F at night. Cool, wet soil can delay sprout emergence or cause seed pieces to rot. Seed pieces should be planted about four inches deep, one foot apart, in rows that are about three feet apart. The sprouts or eyes should be planted facing up. Spacing can be adjusted based on the type of potato that is planted. Those with smaller size profiles, such as fingerling potatoes, can be planted closer together, about eight inches apart. However, potatoes planted too far apart can become misshapen or develop hollow heart.
Some gardeners use drip irrigation systems, which slowly deliver water to the base of each plant. Photo by Trina Zavislan.
Gardeners should add an additional two inches of soil around the top of the plant when they start to emerge from the soil. This is called hilling and ensures that the developing tubers are covered by soil and not exposed to sunlight. Mulching is beneficial and can prevent root damage, as roots can extend up to a foot from the base of the plant. Wood chips and straw are acceptable sources of mulch if they effectively block light. Checking frequently for exposed tubers and adding more soil or mulch will keep potatoes from being exposed to sunlight and turning green. Green potatoes should be discarded and not eaten.
Potatoes require consistent soil moisture. Variability such as infrequent or too heavy watering can cause growth cracks, irregular shapes, and hollow heart. Gardeners should determine the appropriate frequency and duration of watering based on the weather, soil type, and water needs of other plants in their garden. Potatoes typically require about two inches of water per week. A rain gauge placed at ground level near the potato plants will indicate how many inches of water the plants receive. The period of highest water need is in late June to early August when the potato foliage is fully developed. This is usually when the plant flowers and the leaves are dark green. As the plants begin to turn yellow and mature in the later summer, gardeners can water less to encourage tuber development and prevent potatoes from rotting.
Gardeners may observe beneficial ladybugs on their potato plants. Photo by Trina Zavislan.
It is important for gardeners to identify and control pests and diseases on their potato plants. This will improve yields, reduce waste, and protect the commercial potato industry in Colorado. Because most home gardeners plant potatoes on a small scale, it is not cost effective to purchase and apply pesticides. Instead, planting crop rotations with nitrogen fixers (legumes) and frequent visual inspection are key to maintaining plant health. If potatoes are grown every year, they should be grown in different areas of the garden each year. Some pests and disease only infect one type of vegetable, and planting it in the same area year after year creates a favorable environment for infection.
Weeds should be identified and removed frequently, as they can act as hosts of potato disease and compete for water and nutrients. Weed control is especially important while the potato plants are less than a foot tall and fast growing weeds can outcompete the young potatoes. Most weeds thrive on disturbance to the soil and can even grow from fragmented root pieces, so it is best to pull them out by as much of the root as possible instead of cultivating them into the soil with a hoe or rake. This also prevents tuber and potato root damage.
Gardeners should monitor their plants for unusual changes, such as this leaf color, which may indicate a disease. Photo by Trina Zavislan.
The best strategy to prevent potato diseases is to avoid conditions that favor disease development. This means maintaining soil moisture, checking regularly for unhealthy plants, and growing disease resistant varieties. Using certified seed prevents most soil borne diseases. Gardeners should check their potato plants regularly, and remove any that appear stunted, yellow, have shriveled leaves, or look different from the healthy potato plants. To avoid the spread of disease, these plants should be put in the garbage, not a compost pile. The most common potato disease gardeners encounter is powdery scab. Potatoes with this disease are still edible, but gardeners may choose to plant a variety more resistant to scab if it is a problem in their garden. Potatoes with red and yellow skin are more susceptible to scab than russet varieties. Rotating crops also helps interrupt the disease cycle and prevents nutrient depletion.
Frequent scouting for pests enables gardeners to identify and respond to insect problems before they become severe. Look on the underside of leaves, around the base of the plant, and other hard to see areas for insect eggs, larvae, and adults. A hand lens
may be helpful to see small insects. Removing juvenile insects reduces the population and prevents the development of a major pest problem. Pests can be removed by hand or using a high-pressure garden hose.
These potatoes are newly harvested. Photo by Trina Zavislan.
Indicators of mature potato plants include vine yellowing, vine death, and skin set, in which the potato skin does not peel off when rubbed. Immature or new potatoes harvested during the summer before the plant is mature should be eaten right away. These potatoes have a thin skin, bruise easily, and are not suitable for storage. Potatoes should be harvested before the first severe frost. If the potato plants are still green close to this time, the vines can be cut to about six inches tall one to two weeks before the desired harvest date. Decreased watering can also help the tubers mature and develop the skin. A fork or large shovel should be used to lift the plants out of the ground and prevent tuber damage. Gardeners can expect about two pounds of potatoes per plant, but this depends on the variety, weather, and pest, weed, and disease pressure.
After harvest, the potatoes should be stored in a dark place with high humidity at 50 to 60F for about two weeks to cure, or set the skin. This can occur in a cooler part of the house, such as a utility room with a portable humidifier. The potatoes are then ready for long term storage in the dark at 40F, which prevents the potatoes from sprouting or shriveling due to moisture loss. The tubers should not be kept in sealed containers, but should be stored in burlap bags or slotted bins conducive to airflow. If they will be eaten within a week, potatoes can be stored at room temperature.
I've been growing potatoes for years and have never had them rotten inside. This is the first year I tried to grow Yukon Golds and was really looking forward to cooking the first nice big golden potatoe. After pealing it, I saw a rotton spot at one end and just hoped it was a small spot. But no! The entire inside of the potatoe is rotten and black. With a hollow space inside.
The plants were SO healthy and in large well drained wooden containers. What could have happened? I've reading all about potatoes this evening and nothing mentions this problem or it's causes. The only really strange thing about this summer has been the lack of sunshine and warmth. So the squashes didn't do well and the tomatoes are just now getting some color on them. I figured the potatoes would be even better than ever with all of this cool weather. Could it have been overwatering that caused this? Even with excellent drainage? Help! I don't want this to happen again and now I am not looking forward to checking on the red potatoe bin.
It's called hollow heart and is usually caused by irrigation or excess rainfall that causes the tubers to grow rapidly. You can cut the black part out and eat the rest of the potato. It might take on a grayish color when cooked, but it's fine to eat.
Here's some more on that, but I've never heard that hollow heart caused the whole potato to be black inside.
I was always told that too much nitrogen fertilizer was used. Learn something new every day. Luciee <^)
Thanks Joan! And you are right, the "entire" inside of the potato wasn't black like I described. Just seemed that way! There was about 1/2 an inch of good flesh all around the black center. I cut another one open tonight and it wasn't any where near as bad. Just a slit split open space down the center with a slight off color to the flesh along the space. I will be more careful with watering. Something that normally wouldn't be a problem if this summer hadn't been so cold and overcaste!
I have experienced a similar problem this year as well. I concluded it was from too much water due to early rains and over irrigating, however I did have a row of newly purchased seed potatoes which are purple skinned and many were as large as grapefruits. The meat of these purples skinned potatoes is white and even the largest ones are excellent tasting. I have yet to find a single one of the purple skinned potatoes which has shown any indication of rotting. My Yukon Gold, Reds and Russets were all planted from seed potatoes which I have saved and grown for more than four years. I have heard it recommend that you should purchase new seed potatoes after four years. Why I don't know, but possibly this too may be part of the problem we have been seeing with the black insides of a number of our other potatoes.
I use wooden apple bins for my raised veggie garden. They are huge. Almost 4ft x 4ft x 3ft deep. Filled with sandy soil and compost. They have excellent drainage and I get the best veggies out of them. I have one bin which has been producing red potatoes for me for over 10 years now. Every year I harvest all but the marble sized ones, add a bit more compost in the spring, and maintain the same way. I haven't had to buy new seed potatoes ever since and I've never seen this problem before. But this has been one foggy and cold summer. Tomorrow it is officially autumn and I never had to turn a fan on even once to cool off. So I am going to blame it on the weather -)
I'll post again when I see if the red potatoes suffered the same fate as the new Yukons.
PedricksCorner, we found no external evidence on the potatoes which had the internal rot so it's going to be difficult to tell how many were affected. After four days of digging, the potatoes were left to dry in the sun for a few hours each day before moving them to a large tarp in the attached garage. From there they were placed in cardboard flats with meat wrapping paper placed on the bottom of the flat. Some are already beginning to rot through. I rotate these potatoes frequently to check for an external damage. We have decided to make hash browns from as many potatoes as possible and freeze them. Even bought another 7.5 cu ft freezer from Lowes. Good thing our kids and grand kids like the 'added value'. If we're not careful we will be hand feeding them all next!