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By Jordan Rainwater
There's an old saying that my grandmother never failed to repeat come suppertime - perhaps you've heard it yourself. "Eat your vegetables," she would say with watchful eyes-as if it was a mantra. And just as we had successfully managed to ingest one helping, she would lovingly pass the bowl of green beans or fresh salad and say, sweetly, "Better have some more, dear." Today, with the advent of the low-carbohydrate diet era, my grandmother's favorite phrase might become, "Eat your vegetables, dear, but no potatoes!" The potato's picture will disappear from the Food Pyramid. There will be no more Mr. Potato Head and the only thing children will be allowed to use potatoes for is paint stamps.
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We'd like to thank Ernie, Virginia, and Paul New, and their hard working crew for promptly shipping our beautiful double-certified seed potatoes.There's still time to get your order in.
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Diago Pedro, Juan Francisco Pedro, Paul New, Juana Beltran, and Monique Cheatum packing potatoes.
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Virginia New labeling and boxing potatoes for shipment.
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But, I dare suggest that potatoes don't deserve such prejudice and persecution and that all of those protein seekers have been led astray by anti-potato propaganda. Potatoes have been an important part of the human diet since the crop is believed to have first been cultivated in South America's Andean highlands some 8,000 years ago1. In the face of an imminent threat of forever losing our connection to the potato for fear of (gasp!) cellulite, I have concluded that we need to revisit this nearly forgotten vegetable, for fear stems from what we do not understand.
First, back to the basics. The commonly cultivated potato, Solanum tuberosum L., belongs to the Solanaceae family, along with tomatoes, peppers and eggplant. As previously mentioned, it originated in the Andes mountains in South America thousands of years ago. During their exploration of South America in the mid-1500s, Spanish explorers discovered this food crop and brought it back with them to Europe and by the early 1600s the potato had arrived in North America. Potato production in Europe and North America remained limited for nearly a century after its introduction, likely due to the fact that the South American potato strains depended on short days to set tubers. It has taken the last two centuries of dedicated breeding work to adapt the potato to the long days of northern latitudes2. The result of this breeding can be seen in today's standard cultivated potato varieties. Potatoes now join the ranks of rice, corn, and wheat as being one of the world's most important food crops. In the U.S. alone, about 35 billion pounds of potatoes are produced each year.
So, why did the potato become such an important food staple in the first place? Believe it or not, until the recent addition of 'Atkins' as a household name, potatoes were actually celebrated for thier nutritional value. Irish peasants, in the mid-1700s, lived almost exclusively on a diet of potato and milk. Nearly fat-free, potatoes are a good source of vitamin C, potassium and fiber, and a fair source of vitamins B1 and B6. And while it remains that the bulk of calories in a potato are in the form of carbohydrates, potatoes have a surprisingly high amount of protein relative to other vegetables (about 3.6 grams per 200 gram serving, or one medium sized portion3). Clearly, the potato strives to accommodate an array of diet trends.
There is one characteristic about potatoes that I have yet to mention. They are delicious! With hundreds of different varieties, from red to blue and yellow to white, and as many different ways to prepare them, one could hypothetically fix potatoes every night for an entire year and not eat the same meal twice - Hypothetically speaking, of course. In North America and Europe, each potato variety is placed into one of the following categories: Round Red; Round White; Long White; Russet; or Specialty/Novelty. At Seeds of Change, we sell twelve specialty potato cultivars for your culinary delight. A warning to friends of low-carb lovers...serve any of our scrumptious varieties at dinner parties and be prepared to start seeing Potato Eaters Anonymous meetings popping up everywhere.
The remarkable culinary versatility, depth of flavors, and nutritional value that the potato offers are all strong witnesses for the plaintiff potato in the case against the anti-carb craze. But, let's not forget how fun it is to grow them!
Prepare your Site
Before a seed potato is even planted in the ground, an appropriate planting site should be designated in your garden. Choose a spot that will provide full sun to your potato plants to maximize photosynthesis and plant growth. Robust plants will provide the energy and nutrients necessary to produce a fine crop of underground tubers. If you don't have the luxury of a sunny location, potato plants will tolerate partial shade.
Soil type is also important. Potatoes will produce the best tubers in a light, loose, well-drained soil such as a loam, with high organic matter content and good water retention. However, they are rather forgiving plants and will produce a respectable crop even in heavier soils if you deeply cultivate to help create an optimal growing environment for the plant roots and underground stems (stolons), which give rise to potato tubers. Potato plants will thrive in loose, well-draining sandy soils, but because organic matter is generally low in these soils it is important to incorporate a substantial amount of mature compost to provide the plants with nutrients and increase water retention.
Soil pH and Nutrients
Soil pH and nutrient availability play are key considerations in choosing a site to plant potatoes. A slightly acid pH, between 5.8 - 6.8, is ideal for potatoes, but they will tolerate pH as low as 5.0. They thrive on large quantities of nitrogen, potassium, and adequate phosphorus levels. Analyze your soil at home with the LaMotte Soil Test Kit to determine its pH and macronutrient composition in the spring when the soil just begins to warm up. Application rates for amending the soil with macro- or micronutrients should be based on the results of your soil analysis. Keep in mind that phosphorus availability is limited at both high and low pH. Micronutrients such as zinc, iron, and manganese are less available in alkaline soils with pH above 7.5, and macronutrients calcium and magnesium are limited in availability to plants at low pH (below 5.5). Soil pH also influences the development of some potato diseases. For example, the proliferation of common scab is greatest in the pH range 5.5-7.5, and acid scab (primarily an issue in the northeastern U.S.) can be problematic in the pH 5.0-5.5 range. If these diseases are issues in your area, lime can be applied to raise the soil pH. In highly alkaline soils, the incidence of common scab can be reduced by applying elemental sulfur, though the lowering pH effect is not uniform and will be limited to small areas in the plant root zone1. In areas with acid soils, such as many parts of the Northeast U.S., pH can be lowered slightly to 5.0 - 5.2 to control common scab.
Rotate Your Crop to Dodge Disease
Properly rotating your potato plot around your garden will help to reduce the pressure of diseases such as Verticillium wilt, Late blight, and Early blight, Black scurf and many others. Because tomatoes, peppers and eggplants are susceptible to these same diseases, try not to plant potatoes in a space where either of these crops were growing the previous year. If you have the space to work with, a three to five year rotation is even more desirable. If you live where soil pH is acceptably low and potato diseases are not a huge issue, you may choose to designate a potato plot for two to three years where you don't have to apply lime, though you may apply it everywhere else for crops that prefer a slightly higher pH.
Having chosen a site to plant in the garden, it is time to purchase the potato seed. Certified seed is guaranteed disease-free and has been specially grown and maintained by professional potato seed growers. Double certified seed is certified disease-free and certified organic. All Seeds of Change potato seed is double certified.
Planting the Seed
Plant your potato seed four to six weeks before the last expected frost, when the soil temperature has reached at least 50 degrees Fahrenheit. The ideal soil temperature to encourage quick emergence of the potato sprouts with out promoting the growth of decay organisms in the seed piece is between 55 and 60 degrees Fahrenheit. The soil should be moist, but not waterlogged. Though optional, you may choose to pre-sprout your seed potatoes a couple of weeks prior to planting to give the seed potatoes a leg-up on plant development. This can be accomplished by exposing the seed potatoes to an environment of moderate light and temperature. Each seed potato or piece should be about the size of a golfball (two to four ounces) to provide sufficient energy to a new plant, and needs at least two or three 'eyes' from which sprouting occurs. If your seed potatoes are large and you decide to cut them, make certain you wait a day or two before planting to allow the cuts to develop a callous, preventing the seed from rotting and diseases from entering through the wound. A dusting of wood ash on the wound can also help reduce the chance of decay.
If the soil is not too wet, is time to prepare a seedbed. Trying to work the soil when it contains too much moisture will result in soil compaction, poor aeration, and an environment that will promote rotting of the seed pieces. Planting potatoes in rows is the most common method. Each row should be about a foot wide and six to ten inches deep. Space the rows two to three feet apart to allow plenty of extra soil on each side of the row for "hilling" later and for the plant canopies to fill in. Mix in the soil amendments of your choice into each row trench to ensure nutrients will be readily available to the growing plants. Don't overdo the addition of organic matter, however, as superfluous amounts can increase the incidence of potato scab.
You are now ready to plant! Place the potato seeds into the base of the trench twelve to fifteen inches apart. Planting them at closer spacing will result in smaller potatoes at harvest time if you prefer. I would also recommend closer spacing for 'Yukon Gold', as their tubers can grow to beyond desirable size with too much room. If you cut your seed pieces, place them cut size down. Cover your seed pieces with three to four inches of soil to begin, adding another three to four inches of soil when you see the sprouts emerging about two weeks after planting. Another hilling should be done when the plant stems reach about eight inches tall, covering the stem about halfway with soil. It is better to have broad, flattened hills that tall, peaked hills, so pull soil from between the rows to broaden the hills if necessary. This is important because you want the potato plant to send its stolons, or underground stems, evenly about the hill instead of remaining close to the main stem. Tubers set at the distal ends of stolons, and you want there to be plenty of soil to cover the forming potatoes so they don't push out of the hill. If the tubers are exposed to light, it triggers the production of chlorophyll in exposed areas. Chlorophyll is associated with the formation of solanine, a bitter and toxic (in significant quantities) glycoalkaloid that is heat stable and minimally impacted by cooking. So, keep those tubers covered in soil!
Water and Weeds
Once the potato plants begin to grow, even and regular watering becomes essential to promote abundant quantities of shapely tubers. During flowering and immediately afterward is the most vital time for adequate moisture, for this is when the plant is setting new tubers. Keep the soil profile moist, but not wet. Irregular watering is associated with tuber "knobbing" or "chaining", though knobby tubers and other malformed potatoes are largely the result of interrupted growth at high soil temperatures. Excessive water may result in tuber cracking and enlarged lenticels, the 'pores' of a potato tuber. Also, water early in the day to avoid the leaves being wet going into the cool of the evening, lessening their susceptibility to a number of potato diseases).
Good establishment of the leaf canopy over the hills will naturally minimize weed competition and help prevent the soil from drying out. Until then, weed cultivation is critical to reduce the amount of nutrient and water used up by weeds that would otherwise be available to your potato plants. Cultivate with care as not to disturb the potato plant's roots, any developing tubers, and the integrity of the hill.
Pest Control
Depending on your growing region, you may find that you are not the only one interested in your potato crop. After putting in so much care into your developing plants, it can be frustrating to come out to your garden one morning and discover the presence of insect pests, disease symptoms, and even gopher damage.
Perhaps two of the most significant and widespread pests targeting potatoes are wireworms (Limonius spp.) and the infamous Colorado potato beetle (Leptinotarsa decemlineata). Wireworms are actually the yellow to reddish brown, jointed larvae of an adult beetle. Found throughout North America, these one to one and a half inch long worms will bore into the newly planted seed pieces or into the developing tubers, leaving tunnel like holes in the tubers. If they attack early on, they can prevent germination or even kill the plants. They are most commonly found in freshly turned sod. The larvae persist for two to six years before pupating in late summer. In the fall, frequently cultivate to expose and destroy the larvae. Parasitic nematodes may also help5.
The Colorado potato beetle has been the nemesis of potato growers since their introduction to North America. Both the adults and larvae chew the leaves of plants in the Solanaceae family, killing small plants and resulting in yield reduction of mature plants. Adult beetles are rather beautiful with ten black strips running lengthwise down yellow-orange wing covers. Larvae are orange grubs with a distinctive humpback and a row of black spots along the base of each side. Expect two generations in most regions, and three in southern states. Adults overwinter in the soil and emerge in the spring to feed on developing plants and lay their yellow, oval eggs. Eggs hatch within four to nine days. Keeping your plants covered with a light row cover until midseason may be the least time consuming and inexpensive deterrent5. For small crops, hand picking the beetles and larvae daily can keep them under control. For large crops, Spraying BT, an organic insecticide can be very effective.
Disease-wise, Early blight (Alternaria solani), Late blight (Phytophthora infestans) and Verticillium wilt (Verticillium dahliae) are probably the three most common affecting potatoes. All three are fungal diseases. Buying certified disease-free seed will prevent the introduction of Early blight and Late blight pathogens, but these two fungi, if already present, overwinter on diseased tubers and plant debris. Thorough clean-up of plant debris in the fall is essential. Also, if you suspect your plants are infected, pull and destroy the entire plant immediately to reduce the spread to the rest of your crop. Late blight is especially swift in its spread. Rotate your crops, tomatoes too, and look for resistant cultivars. As there is no cure for Verticillium wilt, which is more common in temperate climates, the best method of control is to select resistant varieties. For more detailed information regarding organic control of insects and diseases, the Rodale Institute's The Organic Gardener's Handbook of Natural Insect and Disease Control is an excellent reference.
The information provided in this article should take you through your potatoes' growing season. I will write a second chapter closer to the actual harvest time for potatoes to discuss how to manage your potato crop later in the season, vine-killing, harvesting, and post-harvest handling. In the meantime, I hope that perhaps we Americans will begin to, once again, see the potato in a positive light so that my grandmother's favorite saying will have an all-inclusive meaning for many generations to come.
References:
1 Rowe, Randall C. 'Potato Health Management'. The American Phytopathological Society. 1993.
2 Hortus 3rd Edition. Simon & Schuster Macmillan Company. 1976.
3 Polunin, Miriam. 'Healing Foods: A practical guide to key foods for good health'. DK Publishing, Inc. 1997.
4 Dr. Alvin R. Mosley, Dept. of Crops and Soil Sciences, Oregon State University
5 Ellis, Barbara W. and Bradley, Fern Marshall editors. 'The Organic Gardener's Handbook of Natural Insect and Disease Control'. Rodale Press, Inc. 1996.
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