Quick growing conditions
Air: approximately 12–24°C; nutrient solution: approximately 12–22°C
Around 6.0
Around 1.5–1.6 mS/cm for the research profile
14–16 hours daily; approximately 15–25 kilolux under white LEDs
Suitable systems
- DWC
Substrates
- rockwool
How to Grow Watercress Hydroponically at Home
Watercress (Nasturtium officinale) is a perennial leafy vegetable with a fresh, peppery flavour. It grows well in water-based hydroponic systems and produces edible leaves and tender stems.
Choose true watercress. Garden cress (Lepidium sativum) is a different plant with a shorter growing cycle.
Main Growing Conditions
These settings are practical starting points for indoor growing. Adjust them to your lighting, plant growth and system.
| Parameter | Starting guideline |
|---|---|
| Air temperature | Approximately 12–24°C; cooler conditions slow growth. |
| Nutrient solution temperature | Approximately 12–22°C; it does not need to be warmer than the room. |
| Lighting duration | 14–16 hours daily. |
| Light intensity | Approximately 15–25 kilolux at leaf level under white LEDs. |
| pH | Around 6.0. |
| EC | Around 1.5–1.6 mS/cm for the research profile below. |
| Spacing | Start at approximately 20 cm; allow more room as plants spread. |
The temperature and light ranges are home-growing guidelines, rather than limits established for every variety. Lux readings depend on the lamp spectrum.
Watercress can grow in cool conditions, but warmth within a suitable range can increase growth. Avoid prolonged overheating: temperatures above approximately 29°C can reduce eating quality.
Choosing a Hydroponic System
An aerated deep-water system is a practical choice for home watercress. Support the plants above the reservoir and keep their roots supplied with oxygen.
Watercress naturally spreads. Leave room for branching stems, keep the foliage above the water and prevent roots from blocking circulation. Floating deep-flow hydroponics was used successfully in the study supplying the nutrient profile below.
Recommended Nutrient Profile
This is the same production profile used for dill and parsley in the Walters and Lopez study. Watercress was grown with it too.
All concentrations are in mg/L of the finished nutrient solution. N is total elemental nitrogen; P and K are elemental phosphorus and potassium.
| Element | mg/L |
|---|---|
| N | 200 |
| P | 30 |
| K | 224 |
| Ca | 116 |
| Mg | 64 |
| S | 44 |
| Fe | 2.800 |
| Mn | 0.800 |
| Zn | 1.000 |
| B | 0.200 |
| Cu | 0.800 |
| Mo | 0.200 |
These values are calculated from the fertilizer composition and supplementary magnesium sulphate reported in the methods, before pH adjustments. The researchers maintained approximately pH 6.0 and EC 1.56 mS/cm.
This is a tested growing recipe, rather than a universal optimum for watercress.
Recipe source: Walters and Lopez (2021), “Modeling growth and development of hydroponically grown dill, parsley, and watercress in response to photosynthetic daily light integral and mean daily temperature.”
Use the profile as a starting point and adjust it as your plants develop. Account for nutrients already present in your water, calculate fertilizer quantities from their actual composition and measure the finished solution.
Use our NPK Calculator to prepare your nutrient solution.
Regular Care and Flowering
Check the water level, pH and EC regularly. Maintain aeration, remove dead leaves and keep the reservoir protected from light to limit algae.
Harvest growing tips regularly to encourage branching. Watercress flowers as days lengthen; pollination is unnecessary when growing it for leaves. The flowers are also edible.
When and How to Harvest
Allow approximately five to six weeks from seed for an initial harvest under favourable conditions. The cited experiment harvested watercress after three weeks of initial development and two weeks in the production system.
Cooler conditions or weaker lighting can extend that time. Harvest according to plant size and recovery, rather than a fixed calendar.
Cut tender stems and leave approximately 10 cm of growth for recovery. Take smaller, regular harvests rather than removing all the foliage. Young leaves and stems generally give the best eating quality.
Common Problems, Pests, and Diseases
- Aphids, whiteflies and spider mites: Inspect leaves and growing tips regularly. Isolate affected plants and use physical removal or suitable biological controls.
- Wilting or deteriorating roots: Check aeration, water temperature, circulation and cleanliness before adding more fertilizer.
- Yellow leaves: Check pH, EC, roots and lighting. Leaf colour alone cannot identify a specific nutrient deficiency.
- Algae: Cover the reservoir and keep nutrient solution away from light.
For pesticide-free home growing, prioritise clean equipment, regular inspection and early pest removal.
Use clean water and planting material. Avoid collecting watercress from wild waterways, where contamination may be present.
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