The main difference between determinate and indeterminate tomato plants is the plant's overall size. Determinate plants grow to a set size, making them generally shorter in stature and most often described as "bush" tomatoes. Indeterminate plants continue to produce new upward shoots for as long as the plant lives, resulting in very tall, vine-like plants.
About Determinate Tomato Plants
Determinate tomato plants, as the name implies, grow to a "determined" size, usually no more than 5 to 6 feet tall. Upward growth ceases when the plant produces a terminal flower cluster, or spike of flowers at the crown of the plant. Fruit clusters grow more closely together and tend to ripen all at once and earlier than indeterminate tomato plants. Removing side shoots, or suckers, as they appear is not recommended for determinate variety as it greatly reduces the plant's yield.
Plants marketed as "patio" tomatoes tend to be of a determinate variety, as they are more petite and bushy than their indeterminate cousins. Commercial growers also frequently use determinate varieties as this type of tomato plant produces large amounts of ripe fruit all at once. Popular determinate varieties include Applause, Better Bush, Celebrity, Roma, Rutgers Select and Tiny Tim, a cherry tomato variety.
About Indeterminate Tomato Plants
In home gardens, indeterminate tomato plants are limited in size only by the winter's first killing frost. Under greenhouse conditions, indeterminate varieties can live up to 24 months and grow to between 10 and 20 feet in height. Plants continue to produce new shoot growth at the top of the plant rather than a terminal flower cluster, resulting in an ever-growing vine. Most garden tomatoes are indeterminate varieties, and grow best when trained to a stake or large support cage. When suckers are pruned away, plants produce fewer ripe tomatoes, though each fruit tends to be larger than tomatoes grown on unpruned plants.
Virtually all heirloom tomato varieties are indeterminate, as most determinate varieties are hybrids developed to restrict size and increase yield. Indeterminate varieties that have been continually popular year after year include Stupice, Early Girl, Big Boy and Sungold, though heirloom varieties such as Cherokee Purple, Brandywine and Jubilee have also gained in popularity in recent years for their very large, sweet tomatoes.
Care and Culture
Regardless of the growth habit or variety, all tomatoes have the same care requirements. For optimal growth and fruit production, plants should be situated in very sunny locations, receiving a minimum of six hours of sunlight daily. Tomatoes require consistent watering, though over-watering can lead to cracked fruit. Over-feeding with heavy nitrogen fertilizers lead to lush, green growth but reduced flowering and fruiting; fertilizers with additional potassium and phosphorous ratios promote heavier yield.
Common pests include tomato hornworm and aphids, which can be controlled by inviting beneficial insects to the garden or through judicious use of pesticides. Many tomato varieties now exist that have been bred for resistance to the two main pathogens which attack tomatoes and their relatives: verticillium and fusarium. Nematode-resistant varieties are also available.