Nasturtium (Tropaeolum majus) is a vibrant, easy-to-grow annual treasured for its peppery, edible flowers and rounded leaves. Unlike many garden plants that require consistently damp soil, nasturtiums thrive on a degree of neglect and prefer soil that is not overly rich. Providing too much moisture or nutrients often results in an abundance of leafy growth at the expense of the showy, colorful blossoms. A precise watering approach is necessary to encourage the plant to maximize its flowering potential while maintaining healthy growth.
Establishing the Baseline Watering Schedule
The general rule for watering established nasturtiums is to employ a deep, infrequent method. These plants are drought-tolerant and perform best when the soil is allowed to dry out slightly between watering sessions. For plants growing directly in the ground, provide approximately one inch of water per week, factoring in any rainfall. This approach encourages the development of a deeper, more robust root system, helping the plant withstand periods of heat and dryness.
The most reliable way to determine if an in-ground plant needs water is to check the soil moisture. Before watering, the top one to two inches of soil should feel dry to the touch, confirmed using a simple finger test. Overwatering is the most common mistake, as consistently soggy soil suffocates the roots and promotes root rot. Excess moisture signals the plant to divert energy into lush foliage instead of producing flowers.
Visual Indicators of Water Needs
While checking soil moisture is the best practice, the plant provides clear visual cues about its condition. A mild wilting of the leaves during the hottest part of the midday sun is often a normal reaction to heat and is not a cause for concern. If the wilting persists into the evening or early morning, the plant is signaling a need for water, indicating that the entire root zone is drying out.
Conversely, an overwatered nasturtium often displays symptoms that mimic drought stress, making diagnosis confusing. One sign of excessive moisture is chlorosis, or the yellowing of the lower leaves, while the soil remains damp. This yellowing occurs because the waterlogged roots are unable to absorb oxygen and transport essential nutrients efficiently. Chronically overwatered plants may also develop mushy stems or leaves, which are early signs of fungal disease or root decay.
Adjusting Frequency for Growing Conditions
The baseline watering schedule requires modification depending on the specific growing environment. Nasturtiums planted in containers will dry out much faster than those in the ground due to increased airflow and less soil volume. Small containers, especially those made of porous materials like terracotta, may require daily or near-daily checks, particularly during the summer. Established in-ground plants in a moderate climate may only need water once a week, or sometimes less frequently.
Newly planted seedlings require more consistent attention than mature plants until their root systems are fully developed. During the initial germination phase, the soil must be kept continuously moist to ensure successful sprouting. Prolonged periods of high heat or windy conditions increase the rate of evapotranspiration, accelerating water loss from both the soil and the leaves. Gardeners must increase watering frequency during these environmental stresses to prevent the plants from becoming heat-stressed.