No matter the variety, tomato plants grow with their foliage pointing toward the sky and their roots burrowing deep into the ground. Along with sun, air, and nutrients, water is a crucial part of a tomato plant's health and general development. Without water, tomato plants would not live, and would not produce the fruit for which they are justifiably world-famous.
Water is absorbed into the ground surrounding tomato plants through rainfall. It is also absorbed whenever gardeners water their plants using a hose, bucket, watering can, or other means. If plants are grown near a body of water, water may be absorbed through the soil from that body of water as well.
Composition of the soil in which tomato plants are planted is very important to water absorption. Soils are generally classed in one of three ways: sand, clay, or loam. All soils have a mix of types, but whichever type composes the greatest percentage of a soil's makeup is what determines its identity. Sandy soils do not hold water or nutrients well, and water drains through them readily. Clay soils hold minerals well, and absorb water so readily that they become muddy and compacted. Ideal soil for most plants is loam, which is a mixture of the two soils and other organic matter. Loam soil features drainage sufficient so that tomato plant roots do not rot. At the same time, it absorbs water well enough that those roots always have something to drink.
Underground Tomato Plant Anatomy
Tomato plants feature root systems that grow at roughly the same pace as their above-ground foliage. These roots are what draw water and nutrients up from the ground into the plant, nourishing it. As tomato roots grow, they develop tiny little hairy offshoots that increase the surface area of the roots. This increases a tomato plant's ability to absorb water and nutrients. Tomato plant root systems can grow to a depth of 5 feet underground and 3 feet in width in all directions as they search for water.
The single biggest insect threat to tomato plant water uptake is the root knot nematode. More than 50 species of nematodes exist in garden soil, and most of them are harmless. Root knot nematodes lay eggs on tomato plant roots. The larvae hatch and burrow deep into the roots in search of food. As they feed, they secrete a digestive juice that causes the roots to become severely irritated, and to swell. These swellings are called knots or galls, and when an infestation is severe, can completely prevent uptake of water and nutrients. These pests cannot be seen by the naked eye, and their damage below ground will not be seen unless it is dug up. Foliage above ground wilts and looks unhealthy because it is not getting water or nutrients. Unless gardeners suspect root knot nematodes, the problem may spread. Gardeners who suspect these pests should submit root and soil samples for laboratory testing. A local county extension office can provide information on local facilities offering this service.
Tomato plants require a lot of water to be given in a consistent fashion. On hot days, tomato plants may need to be watered every day or even more often. Tomatoes grown in containers are particularly susceptible to drying out. However, overwatering can result in root rot and may encourage disease. Foliage does not absorb water, and care should be taken when possible to avoid watering foliage when watering tomato plants. Watering foliage can encourage leaf viruses and fungal infections.