antimicrobial

What is Manuka, really?

From Leptospermum scoparium blossom to jar — the botany, geography, and biochemistry of New Zealand's most studied honey.

Sarah L

1 Mar 2026 · Updated 20 Jul 2026

1 min readprimer

A weathered wooden table holds a cluster of small unlabeled glass vessels arranged like a scientist's specimen set: one with raw honeycomb fragments, one with pale amber honey, one with darker aged manuka honey, alongside a scattering of fresh Leptospermum scoparium sprigs with tiny white-pink blossoms and a few dried scrubland twigs. A magnifying glass rests near the blossoms, and a simple wooden dipper drizzles honey into a shallow dish, showing the transition from thin nectar-like liquid to thick mature honey side by side.

The plant

Manuka honey begins with a single species: Leptospermum scoparium, a shrubby tree native to New Zealand and southeastern Australia. It flowers for just two to six weeks each summer, depending on altitude and latitude. Bees must work fast — and beekeepers must place hives precisely within dense L. scoparium stands to ensure monofloral collection.

The plant thrives in poor soils, regenerating scrubland, and coastal margins. It is not farmed; it is foraged. This is part of what makes genuine Manuka honey scarce and difficult to scale.

What makes it different

All honeys are antimicrobial to some degree — most through hydrogen peroxide generated by the enzyme glucose oxidase. Manuka honey is unusual because it contains a second, independent antimicrobial system driven by methylglyoxal (MGO), a compound derived from dihydroxyacetone (DHA) present in the nectar of L. scoparium.

This non-peroxide activity is stable to heat, light, and catalase — unlike hydrogen peroxide activity, which is easily destroyed. It is this stability that makes Manuka honey interesting for clinical applications.

From blossom to jar

The journey from flower to jar involves several stages: nectar collection by bees, enzymatic conversion in the hive, dehydration to below 20% moisture, harvesting, extraction, and — critically — maturation. Fresh Manuka honey contains high DHA but relatively low MGO. Over months of storage, DHA converts non-enzymatically to MGO, increasing the honey's antibacterial potency.

This is why freshly harvested Manuka honey may test lower on MGO assays than the same batch tested six months later.

The grading systems

Several systems exist to grade Manuka honey potency. The most widely recognised is the Unique Manuka Factor (UMF), which combines MGO concentration, leptosperin content, and HMF levels into a single rating. The MGO grading system measures methylglyoxal concentration directly in mg/kg.

Understanding what these numbers mean — and what they don't — is essential for making informed choices about which grade suits your needs.

antimicrobial

Sarah L

Manuka Clinic

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