Is Cold Water Good to Grow Plants?

Outdoor Plants and Soil Temperature

• Soil temperature impacts water and nutrient uptake and controls seed germination and plant growth. Plant germination is slow in cold soil -- 60 to 70 degrees Fahrenheit is best for cool-season plants. Warm-season plants need higher soil temperatures. The deep soil of outdoor plants makes them less sensitive to water temperature extremes than indoor plants, since the soil affects the water temperature as the water percolates through it.

Watering for Frost Protection

• Watering before a freeze can protect plants. Uncovered moist soil can release enough heat to the plant canopy to raise the temperature 2 or 3 degrees Fahrenheit. Heat is also released when water turns into a solid as ice. Sprinkling the leaves with water allows the plant to use this heat. This tactic is useful for periodic or early frosts. Soaking the soil for several days can cause ice buildup, damaging the roots and plant.

Plant Cover

• Gardeners often cover their beds and cold frames during cold spring nights to protect the plant from dropping temperatures and capture the heat radiating from the soil. Frost in the spring damages new plants. A cover can retain the heat near the plant. Once the danger of frost has passed, a mulch cover helps retain the moisture in the soil.

Lukewarm Water

• A rule of thumb for water temperature is that lukewarm water or tepid water is beneficial for plant growth, since it reduces the time it takes for water in the soil to warm to the point plants can absorb it. Leave water to warm in the sun and moderate water temperature before it's applied, when it's practical. Watering early in the morning allows more time for it to warm in the soil during the day so that the water is available to the plants.