Interveinal chlorosis is a yellowing pattern in which the blade between the veins loses colour while the veins stay green, leaving a green skeleton. In cannabis trials, magnesium shortage produced it on lower, older leaves, and iron and manganese shortages produced it on new and upper leaves (Cockson et al. 2019; Llewellyn et al. 2023).
In practice
Use location to split it. Old leaves with interveinal chlorosis: think magnesium, often induced by low root-zone pH or excess potassium or calcium. New leaves: iron (smooth, pale, newest leaves) or manganese (netted, upper-middle leaves with small tan spots), usually from high root-zone pH. Check pH before adding any supplement. Early light bleaching can also leave veins green at the canopy top, so check light intensity too.
Don't confuse with
- Chlorosis in general: any yellowing, including uniform yellowing where the veins fade too.
- Marginal scorch: yellow then brown leaf edges, typical of potassium shortage or salt build-up.
- Light bleaching: pale tops nearest the fixture only.
Manganese (Mn) is a micronutrient that splits water in photosynthesis and activates many enzymes; low pH can raise it to toxic levels.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.Light stress is damage when leaves or buds absorb more light than they can use or dissipate, showing as bleached white or yellow tops nearest the fixture.Yellowing of normally green plant tissue caused by too little chlorophyll, from nutrient shortage, poor root uptake, pH lockout, light damage, pests or normal ageing.The programmed ageing and breakdown of leaves and other tissues, in which the plant recycles nutrients (especially nitrogen) from old leaves to developing flowers and seeds.Salt build-up is the accumulation of unused fertiliser and water salts in the growing medium, raising root-zone EC and causing osmotic stress and lockout-type symptoms.Top shelf is the highest price tier of flower in a shop, used as slang for any premium-looking cannabis; it reflects pricing and appearance, not verified quality.Magnesium (Mg) is a mobile secondary nutrient at the centre of every chlorophyll molecule; deficiency causes interveinal yellowing on older leaves.Iron (Fe) is an immobile micronutrient needed to make chlorophyll and run electron transport; deficiency yellows new leaves between green veins.A mobile nutrient is one the plant can move from older leaves to new growth, so its deficiency shows first on lower, older leaves: N, P, K, Mg, Cl, Mo.An immobile nutrient stays where it is first deposited, so its deficiency shows on young leaves and growing tips first: Ca, S, Fe, Mn, B, Cu.
