Why Volcanic Soil Only

Goal: After this lesson you can explain why kava needs volcanic soil and why a coral atoll cannot grow it. Subject: Geography | Run time: about 6 minutes

Quick recall

Last time we met the plant. Two quick questions. One: where is kava's true home, with the most varieties? Vanuatu, with about 82 (Lebot et al., 1992). Two: why can a continent not grow kava? Its temperature swings too far; kava needs steady island warmth (Lebot et al., 1992).

Why this matters

Not every Pacific island can grow kava. Two islands can sit side by side in the same warm sea, and one grows thick, strong kava while the other grows none. The difference is underground. It is the soil, and the soil comes from fire.

The idea

Kava is fussy about minerals. Its calming compounds, the kavalactones, are produced more strongly when the soil is rich in potassium, magnesium, and iron (Lebot et al., 1992). Where does a tropical island get those minerals? From volcanoes. A high volcanic island is built from lava that breaks down into deep, mineral-rich soil, and its porous rock drains water fast, which protects the roots from rot (Lebot et al., 1992). That is the perfect kava bed. Now compare a coral atoll, a low ring of island built from coral sand. It sits in the same ocean, but its soil is shallow, low in minerals, and poor in organic matter (Lebot et al., 1992). Kava cannot grow there. So across the Pacific, the high volcanic islands, Vanuatu, Fiji, Samoa, the Solomons, grow many kava varieties, while the coral atolls grow none. This is the deepest version of a pattern from earlier episodes. Cacao needed a forest. Guayusa needed a cloud forest. Kava needs volcanic soil. The more specific a plant's geography, the harder it is to move, and the more it stays tied to the people and place that know it.

Picture it

Look at the map on this lesson, the kava islands scattered across the Pacific. Every one of them is a volcano, or built from volcanoes. Now picture a flat coral atoll nearby, a thin ring of pale sand barely above the waves. Same ocean, same warmth, but no kava, because there is no fire in its soil.

Remember this

The fact to carry out: kava needs the mineral-rich, well-draining soil of a high volcanic island, because volcanic potassium, magnesium, and iron boost its kavalactones, and a coral atoll simply cannot provide that (Lebot et al., 1992). Kava's geography is volcanic, and you cannot fake it.

Quick check

Quick check. Why can a coral atoll not grow kava, even in the right climate? Its coral-sand soil is shallow and low in the volcanic minerals kava needs to grow and make its compounds (Lebot et al., 1992).

Key Takeaways

• Kava's kavalactones are produced more strongly in soil rich in potassium, magnesium, and iron (Lebot et al., 1992).
• High volcanic islands provide that mineral-rich, fast-draining soil; kava thrives there (Lebot et al., 1992).
• Coral atolls have shallow, mineral-poor soil and cannot grow kava, even in the same climate (Lebot et al., 1992).
• The more specific a plant's geography, the harder it is to move and the more it stays tied to its people and place.

Sources

• Lebot, V., Merlin, M., & Lindstrom, L. (1992). Kava: The Pacific elixir. Yale University Press.