Every hemp plant has two sides to its biology: the part we can see — stems, leaves, roots — and the part we can smell, taste, and feel. That second side is driven by secondary metabolites, the compounds responsible for aroma, color, resin, and how the plant responds to stress.
For hemp, secondary metabolites aren’t luxuries or decoration. They’re survival tools. When we smell citrus, pine, fruit, pepper, fuel, or floral notes, we’re experiencing the plant’s natural language — chemicals crafted through millions of years of adaptation.
Understanding secondary metabolites explains why some plants are louder, frostier, richer, or more complex than others, and why environment plays such a huge role in terpene expression.
What Are Secondary Metabolites?
Unlike primary metabolites (sugars, amino acids, proteins), which are essential to basic survival, secondary metabolites help hemp:
- Protect itself
- Communicate
- Defend from pests
- Respond to sunlight
- Recover from stress
- Attract pollinators (for seed production)
In hemp, the most important groups are:
- Terpenes
- Flavonoids
- Phenolic compounds
- Phytoalexins
- Resin compounds (including cannabinoids in cannabis varieties)
These compounds shape the sensory experience of the plant and influence its resilience in the field.
Terpenes: Hemp’s Aromatic Defense System
Terpenes are the largest and most expressive group of secondary metabolites.
Hemp produces terpenes for protection, not for us. They help the plant:
- Repel pests
- Prevent fungal growth
- Protect from UV light
- Communicate stress
- Support healing
Common hemp terpenes include:
- Myrcene (earthy, herbal)
- Limonene (citrus)
- Pinene (pine, forest)
- Linalool (floral)
- Caryophyllene (spice, pepper)
- Humulene (woody, herbal)
These compounds are manufactured through the MEP pathway inside the plant’s chloroplasts and trichomes.
What Influences Terpene Production?
- Light intensity
- Temperature swings
- Soil health
- Microbial activity
- Stress signaling
- Genetics
- Humidity
- Nutrient balance
- Hemp expresses terpenes more loudly when it experiences mild, controlled stress — like strong sunlight, cool nights, or wind — which mimic natural conditions.
Flavonoids: The Color, Pigment & Antioxidant Chemistry
Flavonoids give hemp its:
- Purples
- Reds
- Yellows
- Blues
- Deep greens
They also have biological roles:
- UV protection
- Pest resistance
- Antioxidant support
- Anti-stress signaling
Hemp contains unique flavonoids known as cannflavins, which are found primarily in leaves and flowers.
Strong flavonoid expression comes from:
- Genetics
- Light quality
- Temperature swings
- Soil micronutrients
- Healthy metabolic activity
- Cooler night temperatures often enhance purple and red coloration because of anthocyanin production.
Resin & Trichomes: The Plant’s Protective Shield
Resin is a sticky mixture of terpenes, phenolic compounds, and other metabolites.
Trichomes — the tiny glandular structures on hemp flowers — produce this resin.
Trichomes defend the plant by:
- Acting as a physical barrier
- Producing bitter or aromatic compounds that deter insects
- Reducing water loss
- Reflecting UV light
In hemp varieties grown for boutique flower, resin expression is a key indicator of health, vigor, and environmental harmony.
Stress Pathways: How Hemp Decides What to Produce
Secondary metabolites are heavily driven by stress-signaling pathways, especially:
- Jasmonic acid pathway
- Salicylic acid pathway
- Ethylene signaling
- UV-B stress responses
These pathways activate when the plant experiences:
- Insect pressure
- UV exposure
- Temperature swings
- Mechanical stress (wind)
- Drought cycles
- Microbial interactions
When activated in balanced conditions, these pathways elevate terpene and flavonoid synthesis.
Too much stress, however, shuts the plant down instead of stimulating it.
Environment vs. Genetics: The Expression Balance
Hemp genetics determine what the plant is capable of producing.
Environment determines how much of that potential is expressed.
Genetics control:
- Which terpenes are possible
- Trichome density
- Flavonoid profile
- Resin composition
Environment controls:
- Loudness of aroma
- Depth of color
- Resin thickness
- Complexity of flavor
- Stress response intensity
This is why two plants grown from the same clone can express differently depending on environment and soil biology.
Why Secondary Metabolites Matter for Growers
For boutique hemp:
- Aroma complexity
- Bag appeal
- Flavonoid richness
- Frostiness
- Market value
For large-scale hemp:
- Pest resilience
- Field durability
- Environmental tolerance
- Lower chemical intervention
Secondary metabolites don’t just make hemp expressive — they make it strong.