Cannabis defoliation: the technique explained

A hemp plant naturally develops dense foliage during its vegetative growth. As it enters flowering, that density can shade the lower branches and slow air circulation, a factor that favours the development of mould in the dampest areas. Defoliation selectively removes the largest leaves, in particular those covering the flowering sites, without touching the foliage that directly surrounds the young inflorescences.

Three objectives generally motivate the practice: improving light exposure for the lower branches, reducing stagnant humidity around dense foliage, and making manual work easier (inspection, treatment, harvest). Better air circulation also limits the risk of grey mould (Botrytis cinerea), a constant concern both under cover and in open fields.

Growers generally step in at two moments: right at the start of flowering, to lighten the structure before the inflorescences develop, then more lightly a few weeks later if the foliage becomes too dense again. Measured defoliation removes the large fan leaves least exposed to the light, without exceeding a third of the total foliage in any single operation. The aim remains balance: a completely stripped plant loses its photosynthetic capacity and produces less well.

Overly aggressive defoliation stresses the plant and may slow its development rather than improve it. Removing too much foliage at once reduces the photosynthetic surface available, which penalises the growth of the inflorescences rather than encouraging it. The gesture calls for experience: professional growers assess the condition of each plant before acting, rather than applying a uniform rule.

In France, hemp cultivation remains restricted to registered farmers, using varieties listed in the official European catalogue and respecting a THC level regulated at field level. Cannabis cultivation by a private individual, including of low-THC varieties, is not permitted outside this declared professional framework. Flowers and leaves from this sector can, on the other hand, be legally marketed, provided the finished product contains no more than 0.30% THC, in accordance with the Conseil d'État decision of 29 December 2022.

Does defoliation apply to all hemp varieties?

The general principle applies broadly, but the intensity varies according to the natural density of each variety's foliage. Some more open varieties call for a lighter intervention.

Can you grow hemp at home in France to observe this technique?

No. Cannabis cultivation, including of low-THC varieties, remains restricted to registered farmers in France, outside any unregulated individual use.

Does defoliation reduce the quality of the final product?

Well managed, it is rather associated with better airflow and therefore a reduced risk of mould. Poorly managed, excessive leaf removal can on the contrary penalise the plant's development.

How can you recognise legal hemp from a regulated crop?

Check the finished product's certificate of analysis, which must confirm a THC level in line with the legal threshold of 0.30%, along with the grower's traceability.

• Conseil d'État, interim order, 24 Jan. 2022, no. 460055 — primary
• Conseil d'État, 29 Dec. 2022, no. 444887 — primary
• Cour de cassation, criminal division, 14 Jan. 2025, series of rulings (24-81.076, 24-81.078, 24-81.365, 23-84.130, 23-85.359) — primary