Growing herbs in containers offers a convenient way to access fresh flavor, but it requires careful attention to moisture levels. The most frequent cause of failure for potted herbs is improper watering, often due to overwatering. Determining how often to water means moving away from a fixed schedule and relying on key indicators from the plant and its soil.
Determining the Need to Water
Watering frequency must be determined by the soil’s current moisture content, not a fixed schedule. The best way to check is to push your index finger one to two inches deep into the potting mix. If the soil at this depth feels noticeably dry, it is time to water.
If the soil feels cool, damp, or particles stick to your finger, hold off on watering. Most potted herbs, especially those with woody stems, prefer the soil to dry out slightly between cycles. This period of dryness allows oxygen to reach the roots, preventing root rot and encouraging a strong, deep root system.
Factors Influencing Watering Frequency
The rate at which the soil dries out is highly variable, depending on environmental conditions and the type of container used. Sunlight intensity, temperature, and humidity all directly affect how quickly water evaporates and is transpired by the plant. A pot in direct summer sun may need water daily, while the same pot indoors in winter may only need water every five to seven days.
The container’s material and size also play a significant role in moisture retention. Porous materials like unglazed terracotta allow water to evaporate through the pot walls, causing the soil to dry out much faster than plastic or glazed ceramic. Small pots hold a smaller volume of soil and dry out much more rapidly than large planters.
Herb type is another major factor. Mediterranean herbs, such as rosemary, sage, thyme, and oregano, are adapted to drier conditions and require the soil to dry out more thoroughly. Conversely, herbs like basil and mint prefer more consistently moist soil and will need water sooner. Grouping herbs with similar water needs is helpful to avoid under- or overwatering a mixed container.
Effective Watering Techniques
When watering, apply it slowly and deeply to saturate the entire root ball. Pour water over the soil surface until it flows freely from the drainage holes at the bottom of the pot. This deep watering ensures moisture reaches the lowest roots, promoting deep growth.
After watering, check the saucer or drip tray beneath the pot. Excess water should be discarded after about 15 to 20 minutes. Allowing the pot to sit in standing water causes the soil to wick moisture back up, leading to a waterlogged environment and increasing the risk of root suffocation and disease. Direct the stream at the soil level rather than splashing the leaves, as wet foliage can create favorable conditions for fungal diseases.
Recognizing Signs of Watering Stress
Observing the foliage is a reliable way to diagnose a watering problem. Underwatered herbs typically exhibit a noticeable wilt, and their leaves may feel dry and brittle, often developing crispy brown edges or tips. This wilting is a rapid loss of turgor pressure, which can often be corrected with a deep, thorough watering.
Overwatering is a more common killer of potted herbs. Symptoms include the yellowing of lower leaves and a general droopiness, even when the soil is moist. This wilting is caused by root rot, where damaged roots are unable to take up water, mimicking drought symptoms. If the soil smells foul or the stems feel mushy near the base, the roots are rotting due to a lack of oxygen.