How to grow watercress
Overview
Watercress is a semi-aquatic perennial herb grown for its crisp, peppery leaves. It thrives in constantly moist, part-shaded positions and needs consistent clean water to prevent bitterness and bolting. A fast-growing cut-and-come-again crop ideal for weekly kitchen harvests.
Varieties
- Common Watercress — Standard variety with peppery flavour and vigorous growth, well-suited to Australian gardens with consistent moisture.
- Broadleaf Watercress — Larger, milder leaves than common watercress, ideal for salads and less prone to bolting in warmer weather.
Soil Preparation
Watercress prefers rich, loamy soil with a pH between 6.0 and 7.0. Before planting, work in plenty of well-rotted compost or aged manure to improve moisture retention. The soil must stay constantly moist but not waterlogged; adding organic mulch helps maintain moisture levels.
Growing Guide
Sow watercress seed 6 mm deep in rich, moisture-retentive soil or in a shallow container of water. Space plants 15–20 cm apart and keep the growing medium consistently damp—never allow it to dry out. Position in bright indirect light with protection from harsh afternoon sun. For best results, grow in a self-watering pot or a boggy patch near a tap or pond. Succession sow every 4 weeks for a continuous supply.
Sowing
Sow seeds 6 mm deep directly into moist soil or in trays filled with seed-raising mix. Germination takes 7–14 days at 15–20°C. Thin seedlings to 15–20 cm apart. Watercress can also be grown from cuttings or divisions of established plants.
Care
Feed every 4–6 weeks with a balanced liquid fertiliser high in nitrogen to support rapid leaf growth. Prune back hard to 5 cm every few weeks to promote bushiness and prevent flowering. Remove any yellowing or damaged leaves promptly to maintain airflow and plant health.
Companion Planting
Plant watercress alongside other moisture-loving herbs like mint, parsley, and chervil. Avoid heavy feeders such as corn, sunflowers, or brassicas that will compete for water and nutrients. Keep watercress away from strongly aromatic plants like rosemary or thyme which prefer drier conditions.
Common Pests & Risks
Aphids cluster on new growth; wash off with a strong spray or apply insecticidal soap. Snails and slugs can decimate young leaves overnight—use beer traps or copper barriers. Caterpillars (e.g., cabbage white) occasionally attack; hand remove or use Bt spray.
Harvesting
Begin harvesting when plants reach 10–15 cm tall, usually 6–8 weeks from sowing. Use scissors to cut stems 5 cm above the base, leaving enough leaves for regrowth. Regular harvesting delays flowering and keeps the plant productive for months.
In the Kitchen
Harvest watercress just before use for maximum freshness and peppery kick. Store in the fridge wrapped in a damp paper towel for up to 5 days. Add raw to salads and sandwiches, or stir into soups and stir-fries at the last minute to retain flavour.
Troubleshooting
Yellow leaves: usually caused by underwatering or nitrogen deficiency—increase water and apply liquid fertiliser. Bolting (going to seed): triggered by heat or dry soil—provide shade and keep consistently moist. Leggy growth: insufficient light—move to a brighter spot with indirect sun. Wilting: severe lack of water—soak immediately and consider self-watering setup. Aphid infestation: treat with neem oil or insecticidal soap.