Ask A Master Gardener – Watering Gardens

Authored by: Carol Shirk

In Wisconsin, some growing seasons have abundant rainfall and others do not. Seldom do we go through an entire season without needing some supplemental watering. Lack of water for even a short period of time can have a detrimental effect on plants as they rely on the water to draw up nutrients from their roots to the rest of the plant. Under drought stress, plants may produce stunted fruit, produce no fruit at all, or may produce tasteless, woody, or unpalatable fruit. Knowing how much, when, and how to provide water is a key factor in gardening success.

Photo Credit: C. Shirk

Average gardens will need an inch of water per week to thrive. Different soil types may require a different approach, as sandy soils will dry out more quickly and heavy clay soils will hold water longer. Using your finger to test the depth of soil moisture is the surest way to test when you need to water. Although the surface may be dry, there may be moisture below. If it is dry to a depth of two inches, it is time to water.

One of the worst practices is to water your garden lightly every day or every few days. This frequent sprinkling provides water to only the top layer of the soil and promotes shallow root systems. In turn, these shallow root systems are susceptible to rapid drying out and ultimate demise. Instead, water thoroughly, slowly, and deeply once a week. This applies to lawns and trees as well as gardens of all types.

The best time to water the garden is early in the morning. You want to do your best to soak the soil to a depth of 4–6 inches. Overhead watering (sprinklers) is the least efficient and least preferred method of watering. Far too much of the water is lost to evaporation. In addition, overhead watering leaves a longer “leaf wetness period” which substantially increases the risk of fungal disease. Instead, use a soaker hose, drip irrigation, or watering wand.

Smaller gardens can easily be watered with a watering wand. Travel from plant to plant or row to row and apply the water to the base of the plants, lingering about 30 seconds at each with the water at lower pressure. Make two passes and this should get the desired 4–6 inch depth of moisture into the soil. An innovative method to provide irrigation for tomatoes and larger plants is to cut the tops off of gallon milk jugs. Poke several holes in the bottom and sink two of them per plant several inches into the ground. Fill them once or twice per week with water. The water will slowly drain at root level for the tomatoes.

Larger gardens, raised beds, trees, and shrubs can be watered using soaker hoses or drip irrigation systems. Soaker hoses work well for trees and raised beds. They ooze out water directed specifically where needed without waste. For larger spaces, consider a drip irrigation system. Colorado State University has an excellent publication dealing with details of drip irrigation systems:

Regardless of the system used for supplemental watering, a good organic mulch is advantageous in the vegetable garden. The addition of grass clippings, clean straw, or chopped leaves will help retain moisture. Wood chips or shredded bark are good options around trees, shrubs, and in perennial gardens.

Carol Shirk

Master Gardener Volunteer

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