Wisconsin Fast Plants (Brassica rapa): Growth Height and Conditions

Typical Height Range

Under standard classroom/lab conditions (24-hour fluorescent light, 22–26°C, continuous watering via wicking system, peat-based soilless mix, fertilizer), Wisconsin Fast Plants (Brassica rapa) typically reach 15–30 cm (6–12 inches) at flowering (14–18 days post-germination) and 30–45 cm (12–18 inches) at seed maturity (35–40 days).

Factors Influencing Height

Standardized Protocol (Wisconsin Fast Plants Program)

1. Seeds: Standard Rapid-Cycling Brassica rapa (RCBr) stock.
2. Growing system: Quads (4-cell) or film cans with wicks, reservoir with Peters 20-20-20 (1:500).
3. Light: 24h cool-white fluorescent, ~200–300 µmol·m⁻²·s⁻¹ at canopy.
4. Temp: 23±2°C.
5. Thinning: 1 plant/cell at day 3–4.
6. Measure: Height from soil to apical meristem (not flower) daily from day 7.

Educational Use

The predictable, rapid life cycle (seed → seed in ~40 days) and measurable phenotypic variation make Fast Plants a model organism for teaching:

• Quantitative genetics (artificial selection on height, trichomes, anthocyanin).
• Plant physiology (gibberellin response, phototropism).
• Ecology (competition, herbivory simulation).
• NGSS-aligned investigations (inheritance, variation, environmental influence).

Troubleshooting Short Plants

• Leggy, pale, <10 cm at day 14: Insufficient light (intensity or duration).
• Stunted, dark green, purple stems: Phosphorus deficiency or cold.
• Yellowing lower leaves: Nitrogen deficiency or overwatering/root rot.
• Wilting despite wet wick: Root damage (fungus gnats, Pythium) or fertilizer burn (EC too high).

Conclusion

While 6–12 inches (15–30 cm) at flowering is the textbook answer, actual height is a sensitive phenotype reflecting the interplay of genetics and environment—precisely why Fast Plants are such a powerful teaching tool.