{"id":2117,"date":"2019-10-07T06:03:04","date_gmt":"2019-10-07T06:03:04","guid":{"rendered":"https:\/\/greenmanpublishing.com\/?p=2117"},"modified":"2019-10-07T06:03:12","modified_gmt":"2019-10-07T06:03:12","slug":"sweet-potato","status":"publish","type":"post","link":"https:\/\/greenmanpublishing.com\/index.php\/2019\/10\/07\/sweet-potato\/","title":{"rendered":"Sweet Potato"},"content":{"rendered":"\n

Ipomoea batatas<\/em><\/p>\n\n\n\n

Introduction<\/strong>: The sweet potato is native to the Americas and was introduced\ninto Europe very early in the history of European colonization (about 1500).\nMany of the earliest references to the potato probably actually mean this\nspecies. Predictably it didn\u2019t do very well in chilly Northern Europe, but was\ntaken from there to India, China and other tropical countries where it became\nan important food crop.<\/p>\n\n\n\n

Sweet potato should not to be confused with the yam, which is a\nmember of the Dioscoreaceae<\/em> family. It is actually a relative of the\nmorning glory, which is apparent if you see their flowers.<\/p>\n\n\n\n

Crop use<\/strong>: In the right climate the sweet potato is one of the most\nnutritious and productive vegetables you can grow. In places that are too hot\nto grow potatoes it often takes their place as the staple vegetable crop. It\ncan be an important crop for those aiming for\nfood self-sufficiency in warm climates.<\/p>\n\n\n\n

Ease of growing:<\/strong> In a\nsuitably warm climate the sweet potato is pretty easy to grow, though it is\nvulnerable to quite a few pests and diseases. <\/p>\n\n\n\n

Climate<\/strong>: Sweet\npotato is actually a perennial in tropical climates, but in temperate regions\nit can\u2019t survive the cold winters and so must be grown as an annual.<\/p>\n\n\n\n

It does\nbest in a hot, humid climate with a long growing season (ideally 4 – 5 months\nof warm or hot weather) and moderate, evenly distributed rainfall. For best\nquality it needs warm nights (a minimum of\n60\u02daF and ideally over 70\u02daF) as well\nas warm days. In the United States it is most widely grown in the\nsoutheastern states. <\/p>\n\n\n\n

The sweet potato can also be grown in less than ideal conditions, but you have to work at it and give it some protection in cool weather. I\u2019ve done it a couple of times in my garden, but the nights are too cool for it to be very productive. <\/p>\n\n\n\n
About Sweet potato<\/strong> \u00a0<\/strong>
Planning facts<\/strong>
Perennial
Hardiness: Tender
Growing temp: 65 (70 – 85) 95\u02daF
Plants per person: 5
Plants per sq ft: 1
Weeks to grow transplants: 8 – 12
Plant out: 4 weeks after last frost
Days to harvest: 130 – 170 \u00a0<\/strong>

Harvest facts<\/strong>
Yield per plant: 4 oz – 3 lb
Yield per sq ft: 1 – 3 lb \u00a0
<\/td><\/tr><\/tbody><\/table>\n\n\n\n

Nutritional content<\/strong>: Sweet potato is an important\nfood crop from a nutritional standpoint. It is a good source of vitamin C and\nB6, while those with orange flesh are rich in vitamin A (beta carotene). It is\nalso a good source of calcium, potassium and pectin, as well as some beneficial\nphytochemicals including lutein and zeaxanthin. <\/p>\n\n\n\n

Site<\/strong>: Sweet potato is a fast growing and vigorous vine and most types\nrequires quite a lot of space, though there are a few more compact bush\nvarieties. All need as much sun as they can get. <\/p>\n\n\n\n

The plants are quite vulnerable to pests and diseases, so should\nbe rotated regularly. Don\u2019t grow them in the same place again for at least 3\nyears.<\/p>\n\n\n\n

 Soil<\/strong><\/p>\n\n\n\n

pH 4.5 (5.5 \u2011 6.5)7.0<\/strong><\/p>\n\n\n\n

Sweet potato can be grown on soil that is too poor for most crops,\nthough (as is usually the case) better soil will give you a larger crop. The\nideal soil for sweet potatoes is a rich, deep, well-drained, sandy but moisture\nretentive loam. It should be fairly acidic, as disease problems are more common\nin neutral soils. Clay soil can produce slender roots, while poorly drained\nsoils can result in root disease.<\/p>\n\n\n\n

Soil\npreparation<\/strong>:\nIncorporate 2 – 4\u02dd of compost or aged manure into the top 6 – 10\u02dd of soil. No\nmatter what type of soil you have, adding organic matter will be beneficial\nwhen growing sweet potatoes. It lightens a heavy clay soil and improves its\ntexture. It helps a sandy soil to retain moisture (and improves its texture\ntoo). Double digging is a good idea if the soil is heavy.<\/p>\n\n\n\n

Like most\nroot crops sweet potatoes need phosphorus (colloidal phosphate is good) and\npotassium (add greensand or wood ashes). They don\u2019t need a lot of nitrogen, as\nit encourages the growth of foliage rather than roots (and can result in inferior quality roots). <\/p>\n\n\n\n

Ridges<\/strong>: When growing sweet\npotatoes in cooler areas, the soil is often shaped into ridges, as these warm\nup (and drain) faster than flat soil. This doesn\u2019t always work in hotter areas,\nor with very sandy soil though, as they tend to dry out too quickly.  <\/p>\n\n\n\n

Lighter soil can be shaped into ridges 6 – 8\u02dd high and 12\u02dd wide,\nwith 30\u02dd between the ridges. On heavy soil they may be 12 – 15\u02dd wide and 36 –\n48\u02dd apart. Raised beds also work well. <\/p>\n\n\n\n

Planning<\/strong><\/strong><\/p>\n\n\n\n

Where<\/strong>: These creeping tropical vines need plenty of sunlight and a lot\nof growing space. In cooler climates they must be planted in the warmest and\nmost sheltered spot you have. They should also be planted where they can sprawl\nwithout interfering with other crops.<\/p>\n\n\n\n

When<\/strong>: Sweet potatoes are tropical plants and don\u2019t tolerate cold very\nwell, so there is no point in trying to get them in the ground early. Don\u2019t\nplant them out until at least 3 – 4 weeks after the last frost date and the\nsoil is at least 60\u02daF (65\u02daF or higher is better). If you need to gain\nsome extra time you can warm up the soil with black plastic for a couple of\nweeks before planting. The roots need to be harvested before the soil\ntemperature drops down to 55\u02daF in fall.<\/p>\n\n\n\n

Buying plants<\/strong>: In many areas of the country slips aren\u2019t readily available and\nyou may have to buy them by mail order. <\/p>\n\n\n\n

Planting<\/strong><\/strong><\/p>\n\n\n\n

Sweet potatoes are propagated vegetatively by means of shoots\ntaken from the tubers, known as slips. Whole tubers aren\u2019t usually planted\nbecause they send out too many shoots which would eventually compete with each\nother.<\/p>\n\n\n\n

Though sweet potatoes are usually fairly easy to grow, I have\nencountered a problem in obtaining planting material. In traditional sweet\npotato growing areas (the southeast) they can be purchased from nurseries and\nin most other areas they can be bought by mail order (these don\u2019t always arrive\nin the best shape, but usually do fine). <\/p>\n\n\n\n

My problem in California is that you can\u2019t buy them locally and\nyou can\u2019t easily buy them by mail order from another state because of\nquarantine restrictions (though there are some exceptions). I have got around\nthis problem by raising my own slips from tubers I buy at the store. There is some danger of introducing virus diseases\nwhen using shop tubers though and it is better to use certified disease free\nslips where possible. <\/p>\n\n\n\n

Starting your own slips<\/strong>: It is pretty easy to grow your own slips if you have some\nunsprayed tubers. The best source of tubers are those you have grown yourself,\nso it is a good idea to save a few of the best ones (they should be fairly\nthick, at least 1 \u00bd\u02dd in diameter). <\/p>\n\n\n\n

You can also use organic tubers from the\nsupermarket or health food store. Avoid conventional tubers as they are\ncommonly sprayed with a sprout inhibitor, in which case they won\u2019t sprout. <\/p>\n\n\n\n

Indoors<\/strong>: Start sprouting the tubers 2 – 3 months before you want to plant\nthem out. The usual way to do this is to half bury them in a bed of damp sand\nor peat moss (some people cover them with plastic to retain moisture). They\nshould be kept at a temperature of 70 – 90\u02daF (the warmer it is the faster they\nwill sprout). In 4 – 8 weeks they should produce a number of vigorous shoots\nwith healthy roots on them. You should be able to get 10 – 12 slips per tuber. <\/p>\n\n\n\n

Commercial operations sprout the tubers with\nbottom heat and you might want to try this. In the old days this was done in\nhot beds filled with fresh manure, covered with a few inches of sand or soil.\nNow it is done with electric soil heating cables.<\/p>\n\n\n\n

You can also suspend a tuber half in water with toothpicks (like\nan avocado pit). Just make sure the top (flat end) is upright. I haven\u2019t had\nany luck with this method, as the tuber rotted before it sprouted. Also they\ndon\u2019t tend to have as good a root system.<\/p>\n\n\n\n

When the slips are large enough they are\ncarefully detached from the tuber. You can\nremove individual slips as they get big enough and leave the tuber to produce\nmore. <\/p>\n\n\n\n

If you detach the slip with all of its root\nattached it will recover faster, but you will transfer any disease from the\ntuber. If you cut it an inch away from the tuber it will take longer to\nrecover, but you may leave any disease behind. You can put these in 4\u02dd pots\nuntil they grow roots and then plant out.<\/p>\n\n\n\n

If it\u2019s still too cold outside, you might have to transplant them\ninto bigger (1 gallon) pots, or a deep flat.<\/p>\n\n\n\n

Outdoors<\/strong>: If it is warm enough you can start slips\noutdoors (or under cloches or cold frames) following the procedure described\nabove. <\/p>\n\n\n\n

Planting out<\/strong>: I prefer to plant the slips in individual holes. Make a large\nhole, add a couple of handfuls of compost, along with some wood ashes. Then\nbury most of the slip, leaving just the tip sticking out and make a slight well\nto hold water. If the weather is still cool, cover with cloches to keep them\nwarm and happy. If the weather is hot make sure you give them plenty of water\nuntil they are settled in.<\/p>\n\n\n\n

In some areas you may have to use cutworm collars to protect the\nnewly planted slips. <\/p>\n\n\n\n

Spacing<\/strong>: Sweet potatoes are commonly planted in rows, as it is a lot\neasier to hill them up. Space the plants 12 – 18\u02dd apart, in rows 36 – 48\u02dd\napart. Bush types can be spaced somewhat closer.<\/p>\n\n\n\n

Care<\/strong><\/strong><\/p>\n\n\n\n

These plants are quite independent and don\u2019t really need much care\nonce they are established.<\/p>\n\n\n\n

Water<\/strong>: Established plants are quite tolerant of drought,\nbut the soil should be kept evenly moist (at least 1\u02dd per week) for maximum\nproduction. If water is in short supply then just water while they are young. <\/p>\n\n\n\n

Irregular watering (too wet, too dry, too wet) can cause the\ntubers to crack). <\/p>\n\n\n\n

Too much water isn\u2019t a good idea, as it encourages foliage growth\nrather than root growth.<\/p>\n\n\n\n

Weeds<\/strong>: Sweet potatoes are vigorous plants and weeds aren\u2019t a big\nproblem once they get established, but you will need to weed while they are\nyoung. If they have to struggle against a lot of weeds during early growth it\ncan reduce the harvest by as much as 20%. <\/p>\n\n\n\n

The plants should be weeded 2 – 3 weeks after they go in the\nground (and again 3 – 4 weeks later). If you are using a hoe, don\u2019t go too deep\nas it\u2019s easy to damage the shallow roots. You will also remove weeds later on\nwhen you hill the plants. <\/p>\n\n\n\n

A layer of mulch will help to keep weeds under control (but makes\nit hard to hill them).<\/p>\n\n\n\n

Fertilization<\/strong>: It isn\u2019t necessary to feed the plants, unless the soil is very\npoor, in which case give them a feed of compost tea when the tubers are\ndeveloping. Don\u2019t over\u2011feed, as this can encourage lush foliage growth at the\nexpense of tuber production.<\/p>\n\n\n\n

Mulch<\/strong>: In cool climates a black plastic mulch is often used to give the\nplants extra heat. The slips are planted through slits in the plastic. <\/p>\n\n\n\n

In hot climates an organic mulch may be used to keep down weeds\nand conserve soil moisture. Don\u2019t apply this until the soil has warmed up\nnicely though.<\/p>\n\n\n\n

Hilling<\/strong>: As soon as the plants are making good healthy growth they should\nbe hilled up as this can increase the final yield. Of course this is\nimpractical if you are using black plastic mulch, or if they are not planted in\nrows.<\/p>\n\n\n\n

Problems<\/strong><\/strong><\/p>\n\n\n\n

Frost<\/strong>: Sweet potatoes are very intolerant of cold and any frost will\nkill the tops. <\/strong><\/p>\n\n\n\n

If a late spring frost threatens, you should cover your plants\nwith frost blankets or a few inches of loose mulch (and maybe a cloche or\nbucket for extra insurance). This is usually easy because the plants are pretty\nsmall at this point. <\/p>\n\n\n\n

If an early fall frost threatens, it pays to protect them with\nstraw mulch, cloches or even sheets. This is extra work but you may be rewarded\nwith several more weeks of growing weather. The plants grow rapidly towards the\nend, so there can be a big benefit in leaving them in the ground as long as\npossible. When a hard frost threatens, dig the tubers immediately. Don\u2019t wait\ntoo long as any damage to the tubers will affect their storability. <\/p>\n\n\n\n

Pests<\/strong>: A lot of pests may potentially attack sweet potatoes, but\ngenerally they are so vigorous this isn\u2019t a problem (just make sure they get\nall of the nutrients they need). <\/p>\n\n\n\n

One of the few advantages of growing them in\nthe cooler north is that there are less pests to deal with.<\/p>\n\n\n\n

Pests include: cucumber beetles, cutworms, flea beetles, Japanese beetles,\nnematodes, sweet potato leaf beetles, sweet potato weevils, tortoise beetles,\nwireworms and more. <\/p>\n\n\n\n

Diseases<\/strong>: Sweet potatoes are vulnerable to several\ndiseases, including black rot, fusarium wilt, internal cork, pox, scurf, soft\nrot, stem rot and various fungal, bacterial and viral pestilences. <\/p>\n\n\n\n

Use resistant varieties, certified disease free\nslips, good sanitation, rotation and careful storage to minimize disease\nproblems (some diseases develop during storage). Most diseases are less\nproblematic in the north and in acidic soils. <\/p>\n\n\n\n

Sweet potatoes are vulnerable to several diseases in storage, so\nit is important to harvest carefully (without damaging the skins) and cure\nproperly.<\/p>\n\n\n\n

Harvesting<\/strong><\/strong><\/p>\n\n\n\n

When<\/strong>: You can start harvesting and eating the tubers as soon as they\nreach a useful size. However if you want to store them you must wait for them to mature fully (the lower\nleaves will start to turn yellow and die back <\/p>\n\n\n\n

Sweet potatoes continue to\ngrow and get bigger until cold weather kills the tops, so it is a common\npractice to wait until frost threatens and then harvest. If a forecast warns of\nsevere frost you must harvest before it hits, as it can damage any tubers lying\nnear to the surface). Also harvest before the soil drops to 50\u00b0F as this\ncan result in internal damage. Don\u2019t worry if a lot of the tubers are small,\nthey will still taste good. <\/p>\n\n\n\n

How<\/strong>: The tubers tend to grow vertically and cluster directly\nunderneath the plant (they don\u2019t generally spread out a lot). You will have to\ndig deep to get them whole, without breaking them.<\/p>\n\n\n\n

Always handle the tubers gently as they are\neasily damaged and even a small wound can lead to decay (some gardeners even\nline the harvesting container with soft cloth). <\/p>\n\n\n\n

Let the newly harvested tubers air dry for a couple of hours and\nthen brush off excess soil. Don\u2019t leave them exposed to the sun for more than\nan hour though, as this can damage them (some people wait until it is cloudy\nbefore harvesting).<\/p>\n\n\n\n

The next step is to sort the roots into three piles. The first one for seriously damaged tubers, which should be eaten immediately (though they won\u2019t taste as good if not cured) The second pile is for slightly damaged tubers, which should be eaten fairly promptly. The final pile is for undamaged tubers which can be stored.  <\/p>\n\n\n\n

Curing<\/strong>: The flavor of the tubers becomes sweeter after curing, as this\nencourages the formation of an enzyme which converts some of their starch into\nsugar. It also heals minor injuries. <\/p>\n\n\n\n

Remove any excess soil clinging to the roots before curing, but\ndon\u2019t wash them. Cure the tubers by keeping them at 80 – 90\u02daF (with 85 – 90%\nhumidity) for 10 days. If the temperature is only 70\u02daF then leave them for 2 –\n3 weeks. <\/p>\n\n\n\n

Storage<\/strong>: Store the tubers in paper lined boxes in a\ndark, humid, well ventilated place at 50 – 60\u02daF (they may rot if it\u2019s colder\nthan 50\u02daF). This is not only the best temperature range for storage, but also\nencourages the conversion of starch to sugar, so they taste better. <\/p>\n\n\n\n

Sweet\npotatoes don\u2019t like being stored at very low temperatures and can be damaged if\nkept in the fridge for a long period.<\/p>\n\n\n\n

Even under\nthe best conditions sweet potatoes don\u2019t store for very long, If treated well\nthey should keep in good condition for several months (but not much longer).\nThey often decay in storage though, so it\u2019s good to check them frequently for\nrot or deterioration.<\/p>\n\n\n\n

Seed saving<\/strong>:<\/strong><\/p>\n\n\n\n

Sweet potatoes rarely flower outside the tropics and even more\nrarely set seed, so it isn\u2019t used for propagation. <\/p>\n\n\n\n

Save some of the best tubers for propagating slips. These should\nbe stored as described above, but even more carefully, as they need to keep\nlonger. <\/p>\n\n\n\n

Unusual\ngrowing ideas<\/strong><\/p>\n\n\n\n

Cuttings<\/strong>: If you have a long, warm growing season you can propagate sweet\npotatoes by taking green cuttings from growing plants and rooting them in\nwater.<\/p>\n\n\n\n

Indoor plants<\/strong>: Sweet potato vines have been used as indoor plants, though I\ncan\u2019t imagine they produce very much when grown in this way.<\/p>\n\n\n\n

Container growing<\/strong>:\nThe bush varieties have been successfully grown in containers. They are also\nwell suited to grow bags, just be sure to use a fertile mix (see Potato<\/strong> for more on this).<\/p>\n\n\n\n

Animal\nfood<\/strong>: In the south a significant proportion of\nthe sweet potato crop is used to feed livestock.<\/p>\n\n\n\n

Growing in cooler areas<\/strong>: Though sweet potatoes do best where summers\nare long and warm, it is possible to grow them in colder areas, if you are\nprepared to do some extra work. You need to use a fast maturing variety, warm\nthe soil with plastic mulch and maybe even use cloches to keep the plants\nwarmer.<\/p>\n\n\n\n

Interplanting<\/strong>: Sweet potatoes work well with corn,\njust give it a couple of weeks head start.<\/p>\n\n\n\n

Overwintering<\/strong>: Take some of the smaller tubers from your harvest\nand pot them up for the winter. Keep these in the greenhouse or windowsill and\nthe following spring you can separate out the new shoots that emerge and plant\nthem in individual pots. When the right time approaches in spring just plant\nthem out.<\/p>\n\n\n\n

Other\nuses<\/strong>: Sweet potatoes can be used as a temporary\ngroundcover (or a permanent one in tropical areas). <\/p>\n\n\n\n

They can also be used as a soil improving crop to loosen clay\nsoil. <\/strong><\/p>\n\n\n\n

Varieties<\/strong><\/p>\n\n\n\n

Sweet potatoes may be\ndivided into the dry fleshed types and the moist fleshed types (these become\nsweeter and softer when cooked). The skin color ranges from brown, copper, pink\nto purple. <\/p>\n\n\n\n

In marginal northern\nareas the choice of variety is important, as you will need to grow a short\nseason variety such as Georgia Jet. There are also special varieties for\nfeeding livestock that produce abundantly but aren\u2019t so sweet.<\/p>\n\n\n\n

Moist flesh types<\/strong>: The most\npopular and widely used sweet potatoes are of this type.<\/p>\n\n\n\n

Beauregard<\/strong><\/p>\n\n\n\n

Centennial<\/strong> – 90 days<\/p>\n\n\n\n

Covington<\/strong><\/p>\n\n\n\n

Georgia\nJet<\/strong> – 85 to 90 days<\/p>\n\n\n\n

Jewel<\/strong><\/p>\n\n\n\n

O-Henry<\/strong><\/p>\n\n\n\n

Puerto Rico<\/strong> – A compact bush type<\/p>\n\n\n\n

Dry flesh types<\/strong>: These are\nmealier and not quite so popular.<\/p>\n\n\n\n

Japanese<\/strong><\/p>\n\n\n\n

Jersey\nOrange<\/strong><\/p>\n\n\n\n

Kitchen use <\/strong><\/p>\n\n\n\n

The roots should be baked at 350 – 375\u02daF to maximize their\nsweetness.<\/p>\n","protected":false},"excerpt":{"rendered":"

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