San Marzano Tomato Plants & Diseases

History

• Tomatoes are indigenous to South America. Despite the association of tomatoes with Italian cuisine, the vegetable did not make its first appearance in Europe before the 17th century, according to the Arizona State University Yuma County Cooperative Extension. It took some time before Europeans adopted this new foreign food. Italian culinary tradition holds that the seeds to the original San Marzano tomato strain were given to the king of Naples by the Kingdom of Peru in the 18th century, according to the University of California Contra Costa Master Gardener Sharon Gibson.

Types

• Heirloom San Marzano tomatoes are indeterminate plants, meaning they grow on huge, sprawling vines and continue to produce fruit throughout the growing season. Home gardeners who favor the San Marzano texture and flavor continue to grow heirloom, open pollination, indeterminate San Marzano plants, but the straggly vines and failure to ripen all at once made them impractical for mechanical harvest, according to EU-SOL, an agricultural biodiversity project of the European Commission. Plant breeders developed determinate, hybrid varieties that ripen all at once, retaining the name and shape of the San Marzano tomato, but without the heirloom San Marzano flavor.

Cultivation

• San Marzano tomatoes require full sun, well-drained, fertile soil high in calcium and other trace minerals, and a long warm growing season. You will likely only find genuine heirloom San Marzano plants by growing them from seed obtained from specialty heirloom seed vendors and gardener's seed exchanges. Their indeterminate vines require sturdy staking and tying, and regular picking through the growing season. They may not be suitable for growing in cooler, northerly American climates. Hybrids developed from heirloom San Marzanos grow on bushier plants that require only ordinary tomato cages for support. Many of these include "San Marzano" in their name, such as the San Marzano 2 and San Marzano Nano.

Diseases

• The original heirloom San Marzano tomatoes are subject to cucumber mosaic virus. Like other tomatoes, San Marzanos are also subject to late blight, Fusarium wilt, and Verticillium wilt. Modern hybrids like Super Marzano Hybrid VFNT have been bred to resist these diseases, albeit at expense of tomato flavor. Keeping down weeds that host disease-bearing aphids, cleaning tools and hands after working on tomato plants and spraying larger plants with skim milk can minimize the spread of these diseases on heirloom strains, according to the University of Connecticut Integrated Pest Management Program.