The frequency with which you water outdoor herbs is a dynamic process influenced by several garden and environmental conditions. There is no universal schedule, as factors like temperature, soil type, and the herb variety itself constantly change a plant’s moisture needs. Successful herb gardening depends on observing and testing the soil to provide water precisely when required, avoiding both the root damage caused by overwatering and the stress of drought. This approach ensures your herbs develop deep roots, remain healthy, and produce the most flavorful foliage.
Determining When to Water
The most reliable method for determining if an outdoor herb needs water is the simple “finger test.” Insert your index finger about one to two inches deep into the soil near the base of the plant, roughly up to the first or second knuckle. This quick check bypasses the top layer of soil, which often dries out quickly due to sun and wind, to assess the moisture level at the root zone.
If the soil feels completely dry, crumbly, and comes away clean from your finger, it is time to water. If the soil feels cool and moist, or if damp soil particles stick to your finger, delay watering. Saturated soil, which is muddy and squishy, indicates a serious drainage problem or recent overwatering, requiring you to wait until the soil is significantly drier.
Environmental Factors That Change Watering Frequency
Where an herb is planted significantly affects its watering schedule. Container-grown herbs require much more frequent attention than those planted directly in the ground. Containers restrict the root system to a small volume of soil, which heats up and dries out much faster than the surrounding earth. A container herb may need water daily in hot weather, while an identical plant in a garden bed might only need water once or twice a week.
Weather Conditions
Weather conditions are a major variable; high temperatures and strong winds increase the rate of water loss through evaporation and transpiration. Conversely, periods of high humidity or recent rainfall decrease the need for supplemental watering.
Soil Composition
Soil composition also plays a large role. Sandy soils drain rapidly and need more frequent, lighter watering, while heavy clay soils hold moisture longer and require less frequent, deeper watering.
Watering Requirements for Different Herb Types
Even when external factors are the same, the inherent needs of different herb types dictate varying moisture requirements.
Drought-Tolerant Herbs
Many herbs native to the Mediterranean region, such as Rosemary, Thyme, Oregano, and Sage, are naturally drought-tolerant. These woody-stemmed plants prefer their soil to dry out completely between waterings, mimicking their native dry, rocky environments. Overwatering these species is a common mistake and can quickly lead to root rot and diminished flavor.
Moisture-Loving Herbs
In contrast, herbs with lush, softer foliage, including Basil, Mint, Parsley, and Cilantro, require consistently moist soil to thrive. Mint is a notable example, often requiring daily attention in warm weather to keep the soil evenly damp. The goal is to maintain moisture without allowing the soil to become waterlogged or soggy, which can suffocate the roots.
Best Practices for Applying Water
The best time to water your outdoor herbs is during the early morning hours, typically between 6:00 and 10:00 a.m. Watering in the morning minimizes water lost to evaporation before the heat sets in, ensuring roots absorb the most moisture. This timing also allows any water that splashes onto the foliage to dry quickly, reducing the risk of fungal diseases like powdery mildew.
When watering, always aim for a deep soak rather than a shallow sprinkle, which encourages the development of a strong, deep root system. Apply water directly to the soil at the base of the plant, avoiding the leaves entirely. Continue watering until you see drainage from the bottom of a container or until the soil is saturated to a depth of several inches in a garden bed.