Sweet Corn, That Home Garden Favorite For Good Nutrition and Eating Pleasure by E. V. Wann

Sweet corn is a common item in Plymouth, Mass. In Thomas Jeffer- most American home gardens. It pro- son's Garden Book (1810) "shriveled vides a delightful addition to every- corn" is mentioned, which is obvious- day meals, and in season the roasting ly sweet corn. ears are enjoyed for picnics and cook- By 1828 "sugar corn" was listed in outs. Since the days of the Pilgrims, New England seed catalogs. Also, corn-on-the-cob has been a popular evidence indicates sweet corn was American favorite. Sweet corn— being grown by the American Indians either fresh, frozen or canned—may of the upper Missouri by 1833. An- be served as a separate dish or used other early reference to sweet corn in succotash (an American Indian appeared in the Travel Letters (1821) dish), custards, puddings, fritters, of Timothy Dwight as being the most souffles, and stuffed peppers, or delicious vegetable of any known in added to soups and chowders. Sweet this country. corn may also be used in relishes and Sweet corn as a specific crop must mixed pickles. have come into existence at least by Most gardeners will regard sweet 1820 and reached sufficient popular- corn as an essential item in their gar- ity by 1828 to be in a seed catalog. den and take great pride in the good The subsequent history of sweet corn nutrition and eating pleasure it af- is one of variety development. By fords. 1900 there were no less than 63 vari- Corn [Zea mays] is a member of eties, and the first Fi hybrid was in- the grass family, which includes other troduced about 1924. Today, there cereal crops such as wheat, oats, are well over 200 varieties and hy- barley, sorghum, and rice. Corn is brids available to sweet corn growers conveniently divided into six types and gardeners. based on its use and kernel charac- Sweet corn differs from the other teristics. These are , sweet types of corn primarily by its ability corn, , , to produce and retain greater quan- and . They are all of the tities of sugar in the kernels. This same species but differ genetically. characteristic is conditioned by a sin- Dent corn, sweet corn, and popcorn gle recessive gene called sugary-1, are the most commonly grown for symbolized sui. Other less pro- their food and feed value throughout nounced differences are its tender the world. kernels at edible maturity, refined Sweet corn is believed by most au- flavors, a tendency to produce suck- thorities to have originated in North ers at the base of the plant, and America as a mutation from field wrinkled seeds when dried. Dent corn. The first references to sweet corn is considered the "normal" type corn date from 1779; an 8-rowed, red- with all the other types being genetic cob type called Susquehanna, or Pa- variation (mutations] of it. Popcorn, poon, was introduced that year near for example, has very hard starch in the kernels that expands explosively E. V. Wann is Research Geneticist when heated, thus producing the and Laboratory Director at the U. S. fluffy white popcorn kernel. Vegetable Laboratory, Agricultural Re- In recent years a new kind of sweet search Service, Charleston, S.C. corn has come into use that is sweeter

181 they are not pollinating at the same time.

Climatic Needs Sweet corn is essentially a warm- weather crop. It is easily killed by frost and may be seriously injured by prolonged temperatures several degrees above freezing. Germination and emergence of the seedlings are delayed and may be prevented by soil temperatures below 50° F. Sweet corn does best in areas having mean temperatures of 65° to 75° during the required 65- to 100-day growing season. In the Northeast and North Central States this corresponds to the months June, July and August. In central and south Florida, on the other hand, sweet corn is planted fall, winter and spring. Generally, sweet corn can be grown success- fully in the proper season from Mex- ico to Canada and in many other parts of the world. Sweet corn will grow satisfactorily on a wide range of soil types as long Terence O Dnscoll as they are friable and well drained. However, a deep, loamy, naturally than the standard sweet corn. Its rich soil is preferred. Soil should be sweetness is not conditioned by the only moderately acid (pH 5.8 to 6.8). sugary-1 gene but by a similar genetic If the pH is lower than 5.8, lime factor designated shrunken-2 fsh2). should be applied. Have soil tests This gene conditions an even higher made to determine the proper kind level in sugar in the kernels, giving and amount of lime and fertilizer to them a sweeter taste and prolonging apply. Consult your local Agricultural the edible state by three or four days. Extension Agent since most States The different types of corn should have laboratories that provide a soil never be planted together at the same testing service. time. Pollen from dent corn or pop- Available plant nutrients are espe- corn will contaminate sweet corn, cially important early in plant growth. causing the kernels to be starchy and If the plants become nutrient-defi- not sweet. Likewise, the standard cient and stunted, they never fully sweet varieties should not be inter- recover and the yield will be reduced. planted at the same time with the Commercial fertilizers are recom- extra sweet (shrunken-2) varieties, as mended for sweet corn on just about the pollen from one will contaminate all soils throughout the country. Fer- the other—destroying the quality of tilizer recommendations for sweet both. If both types are to be planted corn vary for different sections of the they should be separated by at least country and from one soil type to 400 yards distance, or one planted about four weeks after the other so Well-fiHed ear of sweet corn.

182 another. Again, depend on soil test- In the South and Southwest, after ing for specific recommendations. the tassels show, the plants need rain Some general fertilizer recommen- or irrigation every week. For these dations for typical soils follow: areas, and where soil moisture is • On light sandy soils of the Atlan- likely to be depleted, it is advisable tic and Gulf Coastal Plains, broadcast to provide some supplemental irriga- 20 pounds of 10-10-10 fertilizer per tion. Furrow irrigation is satisfactory 1,000 square feet of area before plant- in most soils where runoff can be ing. Then apply a side dress of nitro- controlled. gen when the corn is in the 6 to 8 Sweet corn varieties differ in the leaf stage at the rate of about a half way their growth is affected by day pound of actual nitrogen (N) per 100 length. Early maturing varieties devel- feet of row (note that Ammonium oped for the North are not recom- Nitrate contains 33 percent actual N mended for the South. They are and Sodium Nitrate contains 16 per- adapted to the long, cool summer cent). days in the North and do not make • On soil of average fertility in the satisfactory growth in the deep South. Northeast, apply 15 to 18 pounds of Conversely the southern varieties are 5-10-5 per 1,000 square feet of area not adapted to the North. When prior to planting and about 3 pounds planted in the North they may not of the same fertilizer banded per 100 silk and tassel until they reach 8 to feet of row at the time of planting. 12 feet in height, and it is too late for • In the more fertile valleys of the them to produce edible corn before West and Pacific Northwest and on frost. Therefore, specific varieties are the rich soils of the Midwest corn recommended for different sections belt, apply in bands 3 to 5 pounds of of the country. 5-10-5 per 100 feet of row at the time of planting- Hybrids The broadcast applications are Fi hybrids have largely replaced the usually worked into the soil before open-pollinated varieties. As with all planting. The band applications hybrid plants, new seed must be ob- should be made when the seedbed is tained for each crop. Seed saved from prepared, about 3 inches to the sides the hybrid plants will not reproduce of the row of seed and 1 to 2 inches true to type and will not retain the deeper than the seed is planted. The hybrid vigor of the parent plants. above rates are based on rows spaced Several public research agencies and 3 feet apart. private companies breed and intro- duce new varieties of sweet corn. As Moisture Needs a result, a large number of excellent Sweet corn requires a continuous hybrids are available for gardeners. and adequate moisture supply for Some hybrids will be available for satisfactory growth and yield. In non- only a few years, being replaced by irrigated areas of the United States, better ones. sweet corn is grown with reasonable Sweet corn variety trials are con- success where the rainfall from April ducted each year by many State agri- through September is 20 inches or cultural experiment stations, and lists more and fairly well distributed- Un- of recommended varieties are pub- less the soil can retain a large supply lished based on these trials. Contact of water, sweet corn will suffer from your State agricultural extension ser- lack of moisture if rainless periods vice for a list of varieties recom- last more than 2 weeks during the mended specifically for your area. growing season. Sweet corn requires plenty of space

183 and is adapted only to larger gardens a serious threat to clean, well nour- exposed to full sunlight. It does best ished sweet corn plantings. Those planted in rows 30 to 36 inches opart that do occur most frequently are with single plants spaced 12 to 16 seedling root rot, Stewart's bacterial inches apart in the row. Overcrowd- wilt, and common . ing the corn will reduce the ear yield Root rot is caused by rot-producing drastically. Planting four or more fungi in the soil. It is often associated short rows is better than one long with a damp, cold soil, and may be row to insure complete pollination. evident as a slight stunting and ir- If the prevailing wind is across the regular plant growth. Seed treatment row, pollen will be carried away from with a fungicide provides good pro- the silks and result in poorly filled tection for the seedling during its ears. early growth. Most sweet corn seeds To conserve space in the garden, packaged and sold commercially to- corn may be planted next to vine day have been treated with a fungi- crops, such as cucumber and can- cide. Use treated seeds whenever taloupe. As the vines grow, they will practical. grow between the corn plants. Stewart's wilt may appear at any Proper seedbed preparation is im- stage of growth, but is most notice- portant for sweet corn in the garden able when plants attain considerable since herbicides are generally not size. It produces yellow to brown used. A clean freshly worked seedbed streaks up to an inch wide on the enables the seedling to emerge rapid- leaves, and may extend the entire ly and get off to a good start ahead length of the leaf. Brown discolora- of grass and weeds. Seed should be tion and sunken cavities form in the planted to a depth of about 1 inch in stalk near the soil line. Plants that moist, heavy soils and 1 to 2 inches become infected early may wilt and in light, sandy soils, depending on the die. Those infected later may be only moisture conditions at planting time. stunted and have streaked leaves. It is generally a good idea to plant The disease tends to be more pre- at approximately twice the desired valent after mild winters and is stand and thin to single stalks at the known to be spread by corn flea desired spacing after the seedlings beetle. There are no sprays or seed have become well established. This treatments effective for controlling will allow for any reduction in seed this disease. germination and for loss of a few Where wilt is suspected of becom- emerging seedlings to insects, birds ing a problem, resistant varieties and other garden pests. About a quar- should be planted. Most varieties de- ter pound of seed is sufficient for veloped in recent years are resistant each 100 feet of row. to the disease, particularly among the Successive plantings are recom- full season maturity group. mended in order to provide a steady Common smut is characterized by supply of fresh corn throughout the the presence of large, fleshy galls on practical harvest season. Also, an the stalks, leaves, tassel and ears. At early, followed by a full season vari- first the galls are silvery white and ety, may be planted at the same time spongy. Later, they turn brown or to give a prolonged harvest period. black, rupture and release large Once the desired stand has been masses of powdery black spores. established, the area should be kept Smut galls are unsightly and render free of weeds by cultivation and the affected ears inedible. Smut is hoeing. promoted by injuries to the plant Diseases: Diseases are generally not during cultivation, by insects, or hail.

184 Again, there are no chemical treat- Several insecticides are available to ments to control the disease. control them. Recommendations for The best means of control is to specific compounds to use and rates avoid injuring the plants, avoid areas of application can usually be ob- viihere smut occurred the previous tained from a reputable garden sup- year, and remove and destroy smut ply center. galls before they break open. This Once the sweet corn becomes es- last step will prevent the spores from tablished and attains most of its plant being released to infect later plant- growth it can withstand a surprising ings. amount of insect feeding without drastic loss of yield. Earworms that begin feeding on the silks and bur- row into the ear tips are difficult to control. Unless the infestation is ex- tremely high and damaging, most gardeners choose to ignore the worm at the tip of the ear, merely clipping off the ear tip and any damaged kernels when the corn is husked. Most State agricultural experiment stations publish current recommen- dations for controlling insects on sweet corn. These bulletins and cir- culars can be obtained by writing to your State Agricultural Extension Service.

Harvesting Sweet corn should be harvested when the kernels are in the milk stage. At this stage the silks are Corn earworm. brown and dry beyond the end of the husks and the ear has enlarged enough to fill the husks tightly to the Insects; Many species of insects are tip. The kernels are about as large known to attack and damage sweet as they will become, but they are still corn at all stages of its growth. Those soft, tender and filled with an opaque that attack the plants early are more milky juice. apt to cause serious damage, and they With some experience the optimum need to be dealt with promptly. These maturity for harvest can be recog- include the southern corn rootworm, nized by sight and feel. The husks cutworms, white grubs, wireworms should never be disturbed to peek at and flea beetles. You can get some the corn as this will permit insects protection against the rootworms, and birds to invade the ear. wireworms, and grubs by using seed Another way to estimate harvest treated with a combination fungicide- time is to note the date of silk emer- insecticide. Cutworms and flea bee- gence on the earliest plants in a row, tles may require an application of then harvest those ears 17 to 24 days insecticide for control. later. The number of days from silk Insects attacking sweet corn later emergence to prime harvest will vary in its growth are corn borers, army- according to weather conditions. If worms, aphids and the corn earworm. days and nights are exceptionally

185 the plant. For best quality, the corn should be picked early in the morning and refrigerated immediately. The sooner it is prepared for serving the better, but it can be held in a re- frigerator (35 to 40° F) for 2 to 3 days with only a moderate reduction in eating quality. To harvest corn, break the ear shank as close to the ear as practic- able without breaking the main stalk or tearing the entire shank from the stalk. Grasp the ear with one hand near its base and bend it sharply downward or to one side with a ro- tary motion of the wrist. The inex- perienced may need to use both hands; hold the shank with one hand warm, prime maturity may be reached 17 or 18 days after silking. If cooler and use the other to snap the ear off. With practice and a strong grip, weather prevails during this period, it may require 22 to 24 days. After the ears of most varieties can be snapped off with one hand. picking a few ears, you usually can Many of the modern hybrids under make an accurate determination about optimum fertility and growing con- harvesting the remainder of the corn ditions will produce two nice ears per at its prime maturity. plant. The top ear will be the domi- Sweet corn passes through its prime nant one, and it will reach prime maturity very quickly. With uniform maturity a day or so ahead of the hybrid varieties the harvest of a sin- second ear. Under such conditions a gle planting will last only about 4 to 100-foot row should yield 100 to 120 5 days. If harvest is delayed the ker- nice ears. nels become tough, starchy and lose their sweet flavor. Sweet corn also loses its quality Fully mature and well-developed ears of rapidly after it has been picked from sweet corn.

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