CBD flower: indoor, outdoor or greenhouse, what changes

Indoor growing takes place inside, under lamps, where the grower sets temperature, humidity and day length. It is often soil-free, which is what "hydro" means on a product page. Outdoor growing happens in the open field, in sunlight, in the ground and with the seasons. Greenhouse growing sits in between: the light stays mostly natural, and the shelter is used to control temperature and humidity in part.

These labels are often used to justify a price, with indoor at the top of the scale and outdoor at the bottom. The measurements available qualify that ranking.

The most useful work appeared in 2023 in the journal Molecules. Its design isolates the effect of the environment: for two Californian cultivars, the researchers compared genetically identical clones grown indoors and outdoors. Outside, the plants grew in full sun, in beds of soil and compost. Inside, they grew under artificial light, in the producer's substrate.

On aroma, the outdoor samples held significantly more limonene, beta-myrcene, beta-caryophyllene and alpha-humulene. The heavier terpenes, or sesquiterpenes, dominated more clearly there. In one of the indoor cultivars, beta-myrcene was not even detectable. Our article on hemp terpenes presents these molecules.

On cannabinoids, the main molecules (CBGA, CBDA, THCA, CBCA) changed little from one environment to the other. The clear difference concerned breakdown products: for both cultivars, CBN, CBNA and other oxidised cannabinoids were far more abundant in the indoor flowers. The authors suggest that, with fewer terpenes, these flowers may be less protected against oxidation. CBN comes from ageing THC, and our comparison CBD vs CBN details the mechanism.

These results have three limits. The sample is small: three samples per condition, two cultivars, a single season. Both cultivars are THC-rich commercial varieties, and neither is CBD hemp. The greenhouse was not part of the comparison, and we know of no published study that compares all three methods at once. The study shows a trend and supports no ranking.

Here the gap is clearest. A life cycle assessment published in 2021 in Nature Sustainability found that indoor growing in the United States emits 2,283 to 5,184 kg of CO2 equivalent per kilogram of dried flower, depending on the region. These emissions come mainly from the electricity and gas used for air conditioning, high-intensity lamps and the CO2 added to speed up growth.

These figures rest on the US power grid and do not apply as they are to France, whose electricity is less carbon-intensive. The order of magnitude still speaks for itself: recreating sun and climate indoors uses energy that an open field does without and a greenhouse needs far less of.

The decree of 30 December 2021 allows cultivation and trade only for Cannabis sativa L. varieties with no more than 0.30% Δ⁹-THC, listed in the EU common catalogue or the French official catalogue. It reserves the growing of flowers and leaves to active farmers using certified seed. On 29 December 2022, the Conseil d'État struck down the ban on selling flowers to consumers, which it found disproportionate.

According to the European Commission, 116 hemp varieties were listed in the common catalogue in 2024, and France supplies more than 60% of EU production. None of these texts mentions indoor, outdoor or greenhouse: the growing method is an agronomic choice and has no legal category of its own. Our guide to the EU variety catalogue explains how to read it.

The growing method tells you how a flower grew without saying precisely what it contains. Three rules follow from that.

1. If you want a pronounced aroma profile, current data lean towards outdoor, which was richer in terpenes in the 2023 study. The greenhouse was not tested there.
2. If you value consistency from one batch to the next, indoor remains the most reproducible environment, with a heavier energy footprint.
3. Whatever you choose, trust the analysis over the label. High CBN against low THC signals an oxidised flower, whatever its origin. Our guide to the certificate of analysis covers each line.

Our product pages state the growing method. Full Gaz grows in the open field in the Drôme, Durban Poison in a cold greenhouse and Skunk indoors. All our CBD flowers show their Δ⁹-THC ceiling. For aroma, drying counts as much as growing, as our article on drying and curing shows. The one on hydro flowers compares three references grown without soil.