Introduction

Harvesting kava (Piper methysticum) is both an art and a science. The timing of harvest, plant maturity, and careful post-harvest handling all influence root quality and total kavalactone content. Traditional Pacific cultivation methods are increasingly supported by research demonstrating how plant age and root type affect chemical composition and yield.

Ideal Age and Harvest Timing

Kava plants develop their characteristic chemistry gradually over time. Research by Siméoni & Lebot (2002) found that by around 24 months, kava roots typically reach a stage of chemical maturity, showing kavalactone concentrations that vary only about ±2% between subsequent samplings. This indicates that plants at roughly two years of age have accumulated substantial kavalactone levels and may be harvested when early yields are desired.

Continued maturation between 3 and 7 years generally increases the overall kavalactone concentration. Studies report increases from roughly 7–8% total kavalactones at 2 years up to 10–12% at 5–7 years, depending on cultivar, soil fertility, and growing conditions. Longer growth periods also allow the development of thicker lateral roots and larger basal corms, improving overall yields.

For small-scale or research growers, harvesting around the 2–3 year mark provides usable root material with good chemistry, while growers seeking premium-grade yields may wait until 4–7 years for peak production.

Root Types: Waka vs. Lewena

Kava roots are traditionally divided into two categories:

• Waka — the lateral roots that extend from the basal stump, typically thinner, more fibrous, and higher in kavalactone concentration.
• Lewena — the basal stump or corm itself, thicker and starchier, often with slightly lower kavalactone content but higher carbohydrate reserves.

Chemical analyses show that waka generally contains 25–50% higher kavalactone content by dry weight compared to lewena. Waka roots often have higher proportions of kavain, dihydrokavain, and methysticin, whereas lewena contains greater relative levels of dihydromethysticin and yangonin. The ratio between these root types influences the plant’s overall chemical profile, which is why traditional Pacific cultivators often separate waka and lewena during preparation.

Harvesting Technique: Step-by-Step Guide

Important: The aerial parts of kava (leaves and upper stalks) contain harmful constituents, including pipermethystine and other undesirable alkaloids. These should never be harvested or included in traditional kava material.

1. Remove the canes: Cut off all above-ground stems close to the crown, leaving only the portion between the first and second node - at most - to avoid including unwanted aerial tissue.
2. Carefully dig up the root system: Gently excavate around the plant to expose both the lewena (basal corm) and lateral roots (waka) without damaging them.
3. Wash thoroughly: Rinse all roots with clean water to remove soil and debris. On farms, growers often use pressure washers. This prevents microbial contamination and ensures accurate chemical analysis.
4. Separate waka from lewena: Remove the lateral roots (waka) from the basal stump (lewena). Lateral roots can be harvested for analysis separately.
5. Skin the lewena: Peel or scrape off the outer layer of the basal corm. This layer may harbor microbes and contains slightly different chemical constituents than the inner root tissue.
6. Cut into manageable pieces: Slice the lewena and thicker waka roots into sections to facilitate uniform drying.
7. Dry: Air-dry roots under shaded, well-ventilated conditions, or use controlled drying at 35–45 °C (95–113 °F). Ensure roots are laid in a single layer with airflow around all sides. Properly dried roots retain 8–14% moisture and have a firm, woody texture suitable for storage or laboratory analysis.

Following these steps preserves chemical integrity, maximizes yield, and ensures that only safe, high-quality root material is collected for research or study purposes.

References

• Siméoni, P., & Lebot, V. (2002). “Genetic and chemical variation in kava (Piper methysticum) cultivars.” Phytochemistry, 61(2), 89–96.
• Lebot, V., & Merlin, M. (1992). Kava: The Pacific Elixir. Yale University Press.
• Lebot, V., & Levesque, J. (1989). “The origin and distribution of kavalactones in Piper methysticum.” Phytochemistry, 28(7), 2053–2060.
• GetKavafied – Practical Kava Farming and Post-Harvest Handling (2023).