Bok Choy Hydroponic Problems & Fixes

Bok choy grown hydroponically encounters inner-leaf tip burn, aphid colonisation, and slow growth when EC is insufficient as its main challenges. Understanding the plant's core thresholds - pH 6.0-7.0, EC 1.5-2.5 mS/cm, water temp 15-22°C, and 10-14h of daily light - helps diagnose problems before they become crop failures.

Quick-Reference Thresholds

| Parameter | Target Range | Warning Sign if Low | Warning Sign if High | |-----------|--------------|--------------------|-----------------------| | pH | 6.0–7.0 | Fe/Mn lockout below 6.0 | Nutrient unavailability above 7.0 | | EC (mS/cm) | 1.5–2.5 | Slow growth; small pale heads | Outer leaf edge scorch | | Water Temp (°C) | 15–22°C | Very slow growth below 12°C | Root stress; tip burn risk above 25°C | | Light (h/day) | 10–14h | Leggy open plants | No major issue for bok choy |

Common Problems & Fixes

| Symptom | Root Cause | Fix | |---------|------------|-----| | Inner leaf tip burn (brown inner leaf edges) | Insufficient transpiration reducing Ca movement to leaf tips - NOT Ca deficiency | Add oscillating fan; do NOT add more Ca; the issue is physical, not nutritional | | Slow, stunted growth | EC below 1.5 or pH out of range | Raise EC to 2.0; check and correct pH to 6.0-6.5 | | Aphid clusters on inner leaves and petioles | Aphid infestation (Myzus persicae or Brevicoryne) | Weekly insecticidal soap spray; introduce Aphidius colemani parasitic wasps | | Yellowing of outer older leaves | Normal senescence OR Fe/Mn deficiency | Check pH; if correct and new growth is green, senescence is normal | | Loose open heads instead of compact plants | Insufficient spacing or excess light hours | Space at 15-20cm; keep to 12h photoperiod |

Normal vs. Worry: What to Watch

• Normal: Outer leaves slightly lighter green than inner leaves - normal light gradient, not a problem.
• Normal: White stem base on some varieties - this is variety-specific colouring.
• Worry: Brown papery edges on the innermost newest leaves - tip burn from poor transpiration; add a fan immediately.
• Worry: Small pale-green insects crowded in the folds of inner leaves - aphid infestation; treat immediately before population explodes.
• Worry: Plants not forming any compact centre at 3 weeks - spacing too tight or EC too low; address both.

Prevention Checklist

• [ ] Run an oscillating fan 15-20 min per hour from day 1 - prevents tip burn without nutrient changes
• [ ] Space plants at 15-20cm centres for compact head formation
• [ ] Maintain EC at 1.8-2.0 after week 2; below 1.5 causes stunting
• [ ] Check pH every 2-3 days; maintain 6.0-6.5
• [ ] Inspect inner leaf folds weekly for aphid colonies - early detection is critical
• [ ] Introduce Aphidius parasitic wasps proactively if aphids are a recurring problem
• [ ] Keep water temp at 15-20°C for best head development