When it comes to water, tomato plants are the Goldilocks of the vegetable garden. Water too much and the roots rot. Water too little, and the plant dehydrates. Worse yet, a tomato plant dying of thirst and one drowning from overwatering look almost exactly the same: wilted leaves, sagging branches, drooping plants. How is the home vegetable gardener to know how to get it just right?
How much water? “An inch a week from you or the sky” is the motto of many successful vegetable farmers (the formula works for lawns and flower beds too). In the more temperate zones, some summers you might not have to water at all to hit this goal. Keep track of the rainfall in your garden with an inexpensive rain gauge. You can pick one up at most hardware stores and garden centers. Tracking the weekly rainfall makes a fun project for kids home on summer break.
What if you forget? Or get distracted?: The Cub Scout campout is this week, your mother-in-law is visiting, or your boss kept you late every night. You know it rained, but you are not sure how much. The sun is blazing, the mulch around your tomatoes is dry, and the plants are wilting. You should water, right? Not necessarily. Remember, a wilting plant can be a sign of under- or over-watering. What matters is how wet it is around the roots of the plant. Ideally, they will dry out completely between waterings (think of it as the roots coming up for air). Take a paint stirrer or similar stick and gently poke it down six inches in the dirt around your plant. If it is wet down there, no matter how dry the surface, don’t water.
How should you water? Tomato plants are happiest if they get their inch of water in one long soaking, preferably early in the morning so the sun can dry off the plants before nightfall. This allows the water to penetrate down to the roots, and the roots to dry out before their next drink. Also, timing your watering for the early morning ensures the leaves don’t stay damp overnight and create a breeding ground for fruit-killing diseases. It is best to end your watering just before the sun rises. Putting your sprinklers on a timer is one way to accomplish this without having to set the alarm for before dawn.
Another strategy is to invest in soaker hoses that deliver water straight to the base of the plant in the slow drip that tomatoes love best. This eliminates the need to water in the early morning (as the leaves won’t get wet), saves water, and ensures you are watering only your plants and not the weeds around it.
In no circumstances should you water your tomatoes frequently and a little at a time. As tempting as it is to just give your plants a squirt a day with the hose, all that is doing is watering the weeds (that grow close to the surface) and encouraging your tomato plant to develop shallow (and less hardy) roots.
An inch of water a week, from you or the sky, delivered in one long session and in a manner that allows the leaves to dry before night, is the perfect formula for healthy, happy tomato plants. Of course, Mother Nature doesn’t always cooperate. However, by keeping good records and testing moistness of the soil correctly, you can properly water when the rains don’t come and keep from compounding the problem when they come too often.
