Introduction to Vegetable Crops

Preface

This web site is a compilation of text, graphics, pictures, and lecture notes given to students in the course, Vegetable Crops (Horticulture 4764), at Virginia Tech. The material in this web site is also relevant to the related course, Vegetable Crops Laboratory (Horticulture 4774).

Acknowledgments

The author wishes to acknowledge the use of topics and information derived from classes taught at the Ohio State University by Drs. E. K. Alban and Dale Kretchman and at the University of California, Davis by Drs. Mas Yamaguchi, Jim Harrington, and Vince Rubatzky. I would like to thank Scott Hudson, Sherry Williams, and Donna Long for their help in compiling this site.

Introduction

Vegetable science, sometimes called olericulture, is one of the most dynamic of the agricultural sciences. The consumption of fresh vegetables has increased dramatically in recent years in the United States. There are approximately 70 major vegetable crops and a total of more than 300 vegetable crops traded commercially in the US.

In addition to renewed interest in fresh vegetables, the diversity of the vegetables consumed has also increased. The number vegetables sold commercially in the United States has increased dramatically over the past twenty years, and it is estimated that at least 300 distinct types are sold commercially throughout the country today. Plant breeders have helped increase the diversity of vegetables by introducing cultivars with nontraditional coloration. For example, some retail stores now carry red lettuce, yellow bell peppers, purple asparagus, yellow-fleshed watermelon, green cauliflower, and purple broccoli.

Vegetables are increasingly traded internationally. It is common to buy vegetables in the United States that were grown in Holland, Mexico, Canada, Honduras, Chile, and New Zealand. American vegetable growers ship fresh broccoli and melons to Japan. Other vegetables produced in the United States are shipped to Central and South America as well as to Europe.

Vegetable production practices have also changed dramatically in recent years. Limited pesticide availability as well as consumer concern over pesticide usage has caused vegetable growers to develop alternative cultural practices that use less chemicals. Minimum tillage practices are increasingly used to reduce soil erosion and limit the use of herbicides. Plastic mulches are widely used to promote earlier crop development, control weed growth, and reduce the amount of water and fertilizer used to produce the crop. Trickle irrigation systems are commonly used to precisely apply water and nutrients to vegetable crops throughout the season.

This course examines the history of vegetable crops, the dietary importance of vegetables as food, and the economic importance of vegetables to the state of Virginia and the nation. I will try to relate some of my experiences as a commercial vegetable grower to you as well. You will also learn practical production information from the Commercial Vegetable Production Recommendations Guide from the Virginia Cooperative Extension Service. The first several chapters cover information that is relevant to the production of all vegetable crops while the later chapters discuss crops individually.

What is a Vegetable?

Most definitions of vegetables are not botanically based. They are based on usage and are rather arbitrary. A vegetable is a herbaceous plant, or portion of a plant, that is eaten whole or in part, raw or cooked, generally with an entree or in a salad but not as a dessert. Of course there are exceptions to this. Rhubarb and melons are both used commonly as desserts. Since "vegetable" is not a botanical term, some vegetables botanically speaking are also fruits. For example, tomato, pepper, bean, and cantaloupe botanically are fruits but because of the way they are used and produced and for historical reasons they are considered to be vegetables.

Fruit is often used in a strictly botanical sense to describe a ripened ovary containing seeds together with adjacent parts that are eaten at maturity. Just to confuse people, there is also a definition of fruit that is also based on usage and is less botanically oriented. By this definition: a fruit is simply a sweet and edible plant structure consisting of a fruit (in the botanical sense) or a false fruit of a flowering plant usually eaten raw or as a dessert. Many true or botanical fruits are not sweet such as tomato, bean etc. and these are the ones commonly referred to as vegetables. Vegetable crops are usually considered high value crops that are intensively managed and should be contrasted with agronomic crops which are extensively grown and less intensively managed.

Wheat, cotton, and rice are all considered agronomic crops. Some crops like Irish potato may be considered as either vegetable or agronomic crops. Some agronomic crops such as tobacco is intensively managed and of high value but are considered agronomic for historical reasons. Corn and soybeans can be either agronomic or vegetable crops depending on the cultivars grown, the time of harvest, and the end use of the commodity. We will discuss these two crops in greater detail later. So these definitions are not perfect and have exceptions. Can you think of exceptions to these definitions?