Foxtailing in Cannabis: Genetics, Environment, or Both?

Foxtailing is a grower term for Cannabis flowers that develop elongated, tower-like extensions instead of remaining uniformly compact. New floral tissue continues to form above or around older parts of the inflorescence, often with fresh stigmas appearing while other parts of the same structure are already more mature.

The term is widely used in Cannabis cultivation, but it is often attributed either to genetics or to stress from excessive heat and light. Research comparing commercial growing environments supports a more nuanced interpretation: genotype and growing conditions can both influence the phenotype, and their relative contribution can differ between cultivars.

Foxtailing across cultivars and environments

Gabriel and colleagues (2025) compared 20 THC- and CBD-dominant Cannabis varieties in two commercial greenhouse environments. One trial used a highly automated commercial greenhouse, while the second used a more variable, semi-controlled greenhouse environment.

Five varieties showed foxtailing in the more controlled environment, compared with 15 in the more variable environment. The same five varieties, Pure 3, 10, 11, 13 and 14, produced foxtailing in both.

The difference between environments indicates that growing conditions influenced expression, while the repeated appearance in the same five varieties suggests a genetic component or predisposition. The study also found significant environmental and genotype-by-environment effects across a range of agronomic and floral traits. Inflorescence characteristics were particularly variable between growing conditions.

A botanical description of foxtailing

In their perspective article on Cannabis flowering terminology, Eckels, Heins and Bugbee (2026) describe late-stage incomplete commercial pistillate flowering as a compact compound inflorescence that continues reproductive growth instead of progressing to senescence. They explicitly associate this phenotype with the grower term “foxtailing”: older parts of the inflorescence may contain senescing stigmas while meristems continue initiating new pistillate flowers.

This describes continued floral development rather than necessarily a return to vegetative growth. During floral reversion, or revegging, reproductive growing points shift back toward vegetative development, potentially producing leafier growth and increasingly vegetative shoots from the inflorescence. Eckels and colleagues distinguish floral reversion as an extreme case in which the inflorescence can revegetate completely. A foxtailed flower is therefore not necessarily reverting. Tooke and colleagues (2005) review the broader botanical distinction between continued flowering and reversion across plant species.

Cannabis flower architecture allows continued development

Spitzer-Rimon and colleagues (2019) described the female Cannabis inflorescence as a highly branched compound raceme. Under reproductive conditions, the plant forms condensed higher-order branchlets containing reduced leaves, bracts, flowers and axillary reproductive structures. The mature bud is not one large flower but a complex branching structure produced through continuing meristem activity.

Cultivars can differ in how this branching develops and eventually terminates. Even under similar conditions, varieties can consequently produce flowers with different density, length and overall architecture. Foxtailing is consistent with this developmental variability, with relatively indeterminate floral growth producing a more elongated structure.

Genetics affects more than flower compactness

The comparison of genetically different varieties in Gabriel et al. helps distinguish cultivar tendencies from responses shared by the crop as a whole. Five varieties retained the foxtailing phenotype in both environments. The authors noted that these did not all belong to one genetic cluster, although several showed genetic admixture that could indicate some shared ancestry.

This does not identify a single foxtailing gene. The genetic architecture of Cannabis inflorescence development remains incompletely understood. Genes involved in flower and meristem development, including MADS-box transcription factors, offer a broader biological framework for investigating floral morphology, but a specific genetic mechanism for foxtailing was not established by this comparison.

A cultivar can therefore have a greater tendency to produce elongated floral architecture even when growing conditions are otherwise suitable. That tendency does not exclude an additional environmental influence.

Environment influences expression

Foxtailing occurred in 15 of the 20 varieties in the more variable environment but only five in the highly controlled greenhouse. Because the experiment compared complete growing environments rather than manipulating one variable at a time, it cannot establish that temperature, light intensity or another individual factor caused the difference.

The findings support an environmental contribution without defining a universal threshold for foxtailing. They also should not be interpreted as proof that all environmentally influenced foxtailing represents injury. Environmental stress and changes in production need to be assessed in relation to the cultivar and the measured outcome rather than inferred from flower shape alone.

A comparison with professional greenhouse crops

Foxtailing is Cannabis terminology, but assessment of reproductive development is familiar in professional horticulture. Greenhouse tomato growers use truss development, flower formation, fruit load, leaf area and growing-point characteristics alongside leaf colour and plant height when evaluating vegetative and generative balance.

Tomato does not produce a Cannabis-like foxtail. The useful comparison concerns the meristem. Tomato inflorescence architecture depends on the coordinated development of several meristem types. Périlleux and Huerga-Fernández (2022) describe how changes in meristem identity and timing can alter flower number, branching and inflorescence structure.

Genetics establishes much of the developmental programme, while crop conditions influence how reproductive growth is expressed. Alberta's commercial greenhouse guidance likewise uses reproductive and vegetative features to assess crop balance. These are horticultural comparisons, not direct evidence for the cause of Cannabis foxtailing.

The visible flower shape is a phenotype. Understanding its cause requires information about cultivar, canopy position and growing conditions, alongside an understanding of how environmental signals influence plant development.

Location within the canopy provides useful information

The distribution of foxtailing can help distinguish possible explanations, although it cannot prove them. If similarly shaped flowers occur throughout a plant and the architecture appears repeatedly in plants of the same cultivar, genetic predisposition becomes a reasonable explanation.

If the strongest foxtailing is concentrated in a particular part of the canopy, environmental differences deserve closer examination. Upper flowers may experience higher photon flux, different leaf and flower temperatures and a different vapour-pressure environment than flowers lower in the crop. Compare affected flowers with flowers from the same plant at other positions before changing the entire cultivation strategy.

Cultivars can respond differently to the same environment. Conditions associated with a stable compact inflorescence in one genotype may be associated with more elongated architecture in another.

Foxtailing does not necessarily mean lower flower yield

Flower appearance and flower mass should be considered separately. In Gabriel et al., foxtailing was associated with differences in inflorescence architecture and density, but lower density did not necessarily translate into lower overall flower yield. The authors interpreted their analysis as suggesting that environmental conditions could shift growth patterns without an equivalent loss of floral mass.

This was not a controlled experiment that induced foxtailing while holding all other conditions constant. The finding should not be interpreted as evidence that foxtailing can never influence yield.

Commercial flower quality also includes compactness, visual uniformity and processing characteristics rather than dry weight alone. Foxtailing can consequently affect the presentation or handling of harvested Cannabis even when flower mass is less affected.

Continued stigma production can confuse harvest timing

Foxtailed inflorescences can continue producing new flowers with fresh stigmas, commonly called pistils by growers. The youngest tissue may appear immature while older parts of the same inflorescence are further through development. Gabriel and colleagues note that this can complicate maturity assessment and post-harvest processing.

Fresh white stigmas at the end of a foxtail should therefore not be used alone to decide that the entire plant needs more flowering time. Harvest assessment should reflect the maturity of the broader inflorescence and plant, not only the newest tissue. This is particularly relevant in cultivars that continue producing small amounts of late floral growth.

When to investigate the environment

Foxtailing alone is not enough reason to make large changes to a grow. If the phenotype is stable across the cultivar, plants otherwise develop normally and measurements indicate suitable growing conditions, the flower shape may largely reflect genetic architecture.

Environmental investigation becomes more appropriate when foxtailing develops unevenly, appears mainly in the most exposed part of the canopy or coincides with other evidence of excessive environmental load. Useful observations include canopy and flower temperature, PPFD distribution and distance from the light source, alongside photoperiod stability, water use and general plant development.

The aim is to determine whether the pattern is consistent with the cultivar or whether growing conditions have changed in a way that warrants correction, rather than trying to remove every elongated floral structure.

Foxtailing is a phenotype rather than a diagnosis

Cannabis naturally has a complex, branching inflorescence architecture. Cultivars differ in how that structure develops, and some show a repeatable tendency toward foxtailing across environments. The greater prevalence in the more variable commercial environment studied by Gabriel and colleagues also demonstrates an environmental contribution to expression.

Genetic predisposition and environmental influence are not mutually exclusive explanations. Observing where the phenotype develops, comparing plants of the same cultivar and checking growing conditions provides more information than diagnosing the plant from flower shape alone.

References

Gabriel, C., Rhode, C., Cronje, C., Wyler, M., Katsir, L., Cropano, C., Vogt, M., Carrera, D., George, G.M., Ruckle, M. & Lloyd, J.R. (2025). Genetic and environmental contributions to agronomic trait variation in Cannabis sativa. Crop Science, 65, e70168. https://doi.org/10.1002/csc2.70168

Eckels, M., Heins, R. & Bugbee, B. (2026). Unraveling the Confusion of Flowering Types and Terminology in Cannabis sativa. HortScience, 61(2), 396–402. https://doi.org/10.21273/HORTSCI19059-25

Spitzer-Rimon, B., Duchin, S., Bernstein, N. & Kamenetsky, R. (2019). Architecture and Florogenesis in Female Cannabis sativa Plants. Frontiers in Plant Science, 10, 350. https://doi.org/10.3389/fpls.2019.00350

Tooke, F., Ordidge, M., Chiurugwi, T. & Battey, N. (2005). Mechanisms and function of flower and inflorescence reversion. Journal of Experimental Botany, 56(420), 2587–2599. https://doi.org/10.1093/jxb/eri254

Périlleux, C. & Huerga-Fernández, S. (2022). Reflections on the Triptych of Meristems That Build Flowering Branches in Tomato. Frontiers in Plant Science, 13, 798502. https://doi.org/10.3389/fpls.2022.798502

Government of Alberta. Tomato plant propagation in commercial greenhouse tomato production. Professional greenhouse guidance on crop balance and plant development, used as a horticultural comparison. Read the guidance.