Week 9 (Unit 17)
Tomato, Cabbage, and other Vegetable Crops
"Vegetable" is a general term that refers to crops that are eaten fresh or preserved in the fresh state. While no one would dispute that lettuce is a vegetable, other crops such as potato, yams, sweetpotato, melons, and watermelon are included in this category in some reports but not in others. Botanically, the foods we commonly call vegetables may be leaves, stems, roots, flowers or fruits.
The World Vegetable Center (AVRDC), based in Taiwan, is an international research center with responsibility for vegetable research and improvement. AVRDC conserves the most diverse collection of vegetable germplasm in the world. Its collection contains more than 50,000 accessions of 334 different species from 151 countries.
|Photo by Keith Weller, USDA/ARS|
Worldwide, at least 10,000 plant species are consumed as vegetables, and about 50 are considered to be of economic importance. Vegetables can be assigned to groups using various criteria, including botanical classification, edible parts, common use, and adaptation.
The table below shows the botanical classification of vegetables, grouped by family. Scientific names are linked to information on a website developed for a course on Vegetable Crops by David Rhodes at Purdue University.
Vegetables can be classified as either warm-season (highlighted in yellow) or cool-season (highlighted in blue). Warm-season vegetables are adapted to mean monthly temperatures of 65° to 85° F and cannot tolerate frost. Cool-season vegetables are adapted to mean monthly temperatures of 60° to 65° F and may be prone to bolting or early seeding at higher temperatures. In general, cool-season vegetables should be stored at cool temperatures.
|Zea mays||sweet corn|
|Brassica oleracea||collards, cauliflower, cabbage, brussel sprouts, broccoli, kale|
|Beta vulgaris||beet, chard|
|Ipomoea batatas||sweet potato|
|Cucurbita maxima||winter squash|
|Cucurbita melo||muskmelon (cantaloupe)|
|Cucurbita moschata||squash, gourd|
|Cucurbita pepo||summer squash, zucchini|
|Phaseolus lunatus||lima bean|
|Phaseolus vulgaris||snap bean|
|Vigna unguiculata||southern pea|
|Capsicum annuum||bell pepper, cayenne, chili pepper|
The figure below shows the vegetables that are produced in greatest quantities worldwide (melons and watermelon are not included).
The leading vegetable crops in the USA in terms of total production are tomato, lettuce, sweet corn, and onion.
|Average yearly production of vegetables in the USA in 2001-2003|
(Mt x 1,000)
|Cantaloupe and other Melons||
|Cucumber and Gherkins||
California and Florida are two key states for vegetable production in the USA.
|Leading states in the value of vegetables, sweet corn and melon sold in the USA in 1997|
Percent of total
The USA is both an active importer and exporter of vegetable crops. Annual imports are close to 5 million Mt and exports are nearly 4 million Mt.
Source: Decoteau, D.R. 2000. Vegetable Crops.
There are four broad categories of markets for vegetable crops: fresh market, processing, forcing, and niche markets. The descriptions below are based on the US experience, but should have parallels in other countries of the world.
Truck farms are major suppliers of the US fresh market. They specialize in large-scale production of just a few crops for long-distance marketing, and are located near major roads and transportation systems.
Market gardens supply a diversity of crops to urban markets. These farms are usually smaller than the truck farms and are located near large cities. They generally produce crops year round under intensive management.
• Pick-your-own (U-pick)
• Farmers’ markets
• Subscription farming – a preseason contract is arranged between the farmer and the consumer for production of particular vegetables.
One model of subscription farming that is becoming popular is CSA (Community Supported Agriculture). The concept was developed in Japan about 30 years ago to address the trend towards increasing importation of food. The Japanese name “teikei” means "putting the farmers' face on food." Supporters in a community purchase shares of the yearly operating budget for a nearby farm. In turn, the farm provides fresh produce to the shareholders throughout the growing season. Thus the community shares in both the bounty and the risk of farming. Many of the CSA in the USA also practice some form of alternative agriculture, such as organic farming.
Raw products are supplied directly from farmer to processor. The profit margin is low, so farms must be very efficient. They are highly mechanized and produce large acreages of just one or a few crops. The choice of variety and management practices are often specified by the processor, who may also provide technical advice during the growing season. In the USA, tomatoes and sweet corn are the vegetable crops with the highest value for the processing market.
This market segment includes the greenhouse industry and others involved in producing vegetables out of season. It comprises a relatively minor proportion of the US vegetable market, but is more important in Europe, particularly in Spain and Holland.
Niche markets specialize in nontraditional crops such as exotic or ethnic vegetables, organic vegetables, herbs, and spices. Increasingly there is a demand by consumers and high-end restaurants for varieties with exceptional eating quality that do not fit well into the mainstream production system e.g., vine-ripened tomatoes and heirloom varieties.
Home gardening continues to increase in popularity, and is presently the number one outdoor leisure activity in the USA. Vegetables are often the main component of home gardens. Formerly, people gardened to save money. Today, people garden for recreation, fresh taste, and better health and nutrition.
5 to 9 A Day for Better Health – this
program is jointly sponsored by the National Cancer Institute
(NCI) and the
for Better Health Foundation (PBH), a nonprofit consumer education
foundation representing the fruit and vegetable industry.
is to increase the consumption of fruits and vegetables in the
United States to 5 to 9 servings every day. The program
also seeks to inform
Americans that eating fruits and vegetables can improve health
and reduce the risk of cancer and other diseases, including
disease, hypertension, diabetes, and macular degeneration.
For more technical information, see the publication on "The health benefits of fruits and vegetables"
The tomato (Lycopersicon esculentum) is a shrubby plant that belongs to the nightshade family (Solanaceae). It is grown as an annual in temperate climates, but can be grown as a perennial in warm climates. The tomato is produced for its fruit, which may be red, yellow, or orange, depending on the variety. Varieties also differ in fruit size, ranging from the cherry tomato to the beefsteak types; and fruit shape, which varies from round to pear shape.
Tomato is a diploid with 2n=24 chromosomes. It has perfect flowers and is self-pollinating.
|Photo by Scott Bauer, USDA/ARS|
Tomato originated in South America, in the midaltitudes of Peru or Bolivia. Many wild forms of tomato can be found in that area today. Although it is native to the Andes, there is no evidence that it was used as a food crop by the Incas. It first gained acceptance as a food crop in Central America and Mexico. In the ancient Aztec and Toltec cultures, tomato was commonly intercropped with corn.
Tomato was taken to Europe by the early Spanish explorers, but for many years it was thought to be poisonous and was only used as an ornamental. Italians first grew the tomato around 1550 and were probably the first Europeans to eat it with any enthusiasm. It was not until the 1800's that it became popular as a food crop in the US.
Determinate varieties of tomato will grow to about 3 to 4 feet in height, but indeterminate varieties may be much larger. In a determinate variety, maximum plant height is attained when the terminal bud produces a flower. Determinate types produce fruit and ripen over a relatively short time span (4 to 5 weeks), making them easier to harvest. Indeterminate types will continue to grow and produce new flowers throughout the growing season. Some cherry tomato varieties are particularly prolific. Indeterminate varieties are commonly used for greenhouse production. Staking may be beneficial for some determinate types, and it is essential for indeterminate varieties. In general, fruit from indeterminate varieties is softer with more gel than the determinate types.
Tomato is a warm-season crop, and cannot tolerate frost. The crop requires from 60 to 90 days from planting to harvest, depending on the variety and environment. It is well-adapted to midaltitude areas of the tropics.
Tomato can be grown on many soil types, but prefers a well-drained, loamy soil that is high in organic matter. Tomatoes are planted directly as seed in the soil, or alternatively may be grown from transplants for an earlier crop harvest.
The management of tomatoes for the fresh market is more intensive than for processing tomatoes, which are usually grown from seed on bare ground without staking. In the USA, plastic mulches are commonly used for commercial production of fresh market tomatoes. Organic mulches such as straw, leaves, grass clippings, or compost can also be used to control weeds, retain soil moisture, control certain diseases and improve fruit quality. Staking, pruning, and caging are also common practices for fresh market tomatoes.
Tomatoes have relatively high requirements for water. From 1 to 1.5 inches of rain or irrigation are needed each week, depending on the temperature, soil conditions, and size of the plant.
|FAO average production statistics for tomato, 2001-2003|
|Country||Area Harv (ha x 1,000)||Production (Mt x 1,000)|
The largest exporters of tomato are Spain (910,000 Mt) and Mexico (848,000 Mt).
About ten million Mt of tomatoes are produced annually in the United States. About 1/8 of that is amount is sold as fresh tomatoes and the rest are processed (this doesn't account for tomatoes grown in backyard gardens.) California and Florida are the top two tomato producing states. These two states have similar shares of the fresh market, but California leads all other states in production of tomatoes for processing.
For a comprehensive guide for integrated pest management of tomato pests and diseases in California, see http://axp.ipm.ucdavis.edu/PMG/selectnewpest.tomatoes.html
Blossom end rot in tomato is a physiological disorder induced by a deficiency in calcium. The requirements of tomato for calcium are relatively high.
Common fungal diseases in the USA include:
Common bacterial diseases in the USA include:
A serious threat for tomato production in lowland tropical areas is bacterial wilt. One approach is to graft tomato on to wild eggplant rootstocks (Solanum torvum), which has resistance to this pathogen.
Tomatoes are grown for the fresh market in the field and in greenhouses. Tomatoes for fresh market are often harvested at the mature green stage for long-distance shipping and then treated with ethylene gas to promote ripening prior to sale. Most varieties of tomato can be eaten fresh.
Tomato is also sold for processing into juice, canned tomatoes, sauces, pastes, and catsup. Processing tomatoes are often treated with an ethylene-producing compound in the field before harvest to promote ripening and to permit once-over machine harvesting. Processing types (Roma) are high in dry matter and have a thick skin to reduce damage during mechanical harvesting.
Tomatoes are nutritious and low in calories. One medium sized tomato provides 40% of the RDA of Vitamin C, 20% of the RDA of Vitamin A, and some calcium, iron, potassium, and fiber.
The red color of tomato is due to the accumulation of a carotenoid pigment, lycopene. Tomatoes at the mature green stage have accumulated all of their nutrients and vitamins. Under natural conditions, the next step in the ripening process - the production of lycopene - is triggered by the release of ethylene from the mature fruit.
|Tomato has been genetically engineered to increase fruit quality. Some GM tomatoes possess a gene that delays ripening by inhibiting ethylene production in the fruit. They can be left longer on the vine, which enhances flavor, without the risk that they will overripen before they are shipped and sold. Another type of GM tomato has been engineered to delay the breakdown of pectin, thereby slowing down another aspect of fruit ripening: softening.|
|Endless Summer, a type of GM tomato with delayed fruit ripening.
Photo by Jack Dykinga, ARS/USDA
Decoteau, D.R. 2000.
| The cole
crops belong to the Brassicaceae or cabbage and mustard
family. These crops are often referred to as Brassicas or crucifers.
All members of this family are cool-season crops, and are thought
to have originated in Europe or Siberia.
Members of this diverse species all descended from an ancient cabbage that probably was much like modern collards and kale. To demonstrate the common ancestry of these crops, and experiment was conducted at the Cirencester Agricultural College in southern England in 1860. Basic breeding and selection procedures were applied to a wild cabbage from the seacoast that resembles kale. Forms of broccoli and other related cabbage-like varieties were developed, demonstrating that rather simple genetic changes can account for the dramatic differences that we see in these crops today.
L. var. italica Plenck
B. oleracea L. var. gemmiferra Zenk
B. oleracea L. var. capitata L.
B. oleracea L. var. botrytis L.
B. oleracea L. var. acephala DC.
B. oleracea L. var. acephala DC.
B. oleracea L. var. caulo-rapa
Cabbage is the most widely grown cole crop in the world today, followed by cauliflower. China and India are the leading producers for both of these crops.
|FAO average production statistics for cabbage and cauliflower, 2000-2002|
|Country||Area Harv (ha x 1,000)||Production (Mt x 1,000)|
|United States of America||105||2,432|
The part of the broccoli plant that is marketable is a head consisting
of immature flowers. Broccoli has two distinct forms, but the one that
we are most familiar with is called "sprouting broccoli". Although
the crop has been cultivated for at least 2,000 years, and was probably
introduced to the Americas about 200 years ago, it did not really gain
wide popularity as a crop in the US until the 1920's. It has been grown
by Americans of Italian descent for generations. Broccoli consumption
in the USA has been increasing steadily from about 2.2 pounds in 1976
to 6.7 pounds per capita per year in 1997. California is the leading producer
in the USA.
Broccoli has a shallow root system and requires a reliable supply of water and nutrients to produce a crop of good quality. Soil pH should be in the 5.5 to 6.5 range to avoid deficiencies of calcium, molybdenum, and boron. High levels of organic matter are also beneficial for broccoli production.
Broccoli is usually grown from seed in single rows or in multiple rows in raised beds. Alternatively, it can be seeded in the greenhouse and transplanted to the field. Harvesting is generally done by hand when the head is still compact, before the flowers open. A typical field may be harvested 4-6 times, at intervals of several days. In the US the heads are often placed in a box with an ice slurry as soon as they are cut. Under ideal conditions, they can be stored for about two weeks.
To maintain its crisp texture and excellent nutrient content, broccoli should not be overcooked. A brief steaming is ideal, but if it must be boiled, use a minimum amount of water and stand the broccoli on its stem to keep the florets out of the water. One serving of broccoli supplies 220% of the RDA of Vitamin C, 15% of Vitamin A, and 6% for both calcium and iron. It is also a good source of folate and dietary fiber. Consumption of broccoli (and other cole crops) may have many health benefits, including:
For more information, see http://www.medizin-forum.de/prostatitis/broccoli-health.html
Like the other Brassicas, cabbage is a cool-season biennial crop that grows best with ample water supply. Cabbage is grown for its leafy head, which is usually green, but some varieties have red and purple heads. The leaves surround the terminal bud on a short, unbranched stem.
Major subgroups of cabbage:
Records of cabbage production date back to 2,500 BC. It is thought to have evolved from a wild, nonheading type of cabbage. The center of origin may be Asia Minor or the Mediterranean region. Cabbage was greatly appreciated by the ancient Greeks, and was widely grown in Europe in the 1400's. The first planting of cabbage in North America was in 1669. By the 18th century, it was being cultivated by some Native American tribes.
Cabbage can be grown as a spring crop in colder temperate climates, as a fall crop in temperate areas with mild winters, and in the midaltitudes in the tropics. It is frost tolerant, and can also tolerate some heat during its early growth stages, provided that heading occurs in cooler weather.
Fields selected for cabbage production should not have been used to grow a cole crop for the past four years, to avoid problems with soil-borne diseases and insect pests. Cabbage may be direct seeded or grown from transplants.
Cabbage is shallow-rooted and must have a dependable supply of water and nutrients. Soils with a pH of 6 - 6.8 that are high in organic matter are most suitable for cabbage. Excessive water during heading should be avoided, however, because the heads are prone to splitting in warm weather.
Harvesting for the fresh market is generally done in stages by hand. Harvesting for storage and processing may be done all at once, either mechanically or by hand.
Cabbage should be stored at temperatures of 32 to 36 °F with high relative humidity. Under these conditions, cabbage may be stored for up to five months.
The major end-uses of cabbage are
A serving of cabbage provides 70% of the RDA of Vitamin C, 4% of the RDA for iron and 2% of the RDA for calcium. It is a good source of fiber.
The head of cauliflower consists of some condensed, malformed flowers called the ‘curd’. The oldest known records of the crop are from the 6th century BC. It was sold in European markets in the 1600’s, and was first reported in the US in the early 1800's.
Per capita consumption in the US is about 1.9 pounds per year. Broccoli is consumed in larger quantities than cauliflower in the US, but worldwide, cauliflower is a more important crop than broccoli. In the USA, California produces far more cauliflower than any other state.
Cauliflower may be direct seeded or transplanted to the field. It has more stringent requirements for optimum production than the other Brassica crops: cool temperatures, plenty of water, plenty of NPK fertilizer. A soil pH of 6-6.5 is needed to ensure adequate availability of molybdenum. The crop is sensitive to unfavorable conditions such as drought, or temperatures that are too high or too low. Environmental stresses may cause premature formation of heads called “buttons” that will never develop properly. In summary, cauliflower is fussier than its cousins. It has been described as "a cabbage with a college education." In India, however, heat tolerant varieties have been developed, which has enabled that country to become one of the leading producers of cauliflower.
Cultivars of cauliflower differ greatly in the time required to reach maturity. Winter types are produced in warmer climates with mild winters. These varieties tend to be larger.
Blanching is an important management practice in cauliflower. The leaves are tied above the developing heads for 5-10 days before harvest to preserve their white color. Self-blanching types naturally curl their leaves over their head and don’t have to be tied, but at present those varieties do not have the high quality required for commercial markets.
Harvesting is done by hand, and the heads are stored at cool temperatures (32-35 °F). Cauliflower is a good source of Vitamin C and fiber.
Take the quiz on this Unit on the Blackboard.
AVRDC. 2004. Learning Center - online resources from the World Vegetable
Decoteau, D.R. 2000. Vegetable Crops. Prentice Hall, Upper Saddle River, NJ.
Halweil, Brian. 2004. Eat Here: Reclaiming Homegrown Pleasures in a Global Supermarket. Worldwatch Institute. 237 pp.
National Geographic. 2000. Our vegetable travelers.
Oregon State University. 2004. Hort 233 Vegetable Crops class notes.
Rhodes, D. 2003. Hort 410-Vegetable Crops class notes. Purdue University.
University of California. 2004. UC IPM on-line.