Plant morphology refers both to the scientific study of the external physical structure and appearance of plants and to the descriptive terminology used to characterize these traits.[1] In this blog post, we’ll provide an overview of the descriptive morphology of Cannabis sativa.
Morphology matters
The morphology of cannabis varies throughout its life cycle in relation to such factors as genetics or strain, environmental conditions and growing techniques. Its height impacts how much light it can receive, as well as its biomass and how well it utilizes resources. Its branching pattern affects how it distributes those resources, buds and flowers, and synthesizes essential oils and cannabinoids. Its structure also plays a role in pest and disease resistance, ease of cultivation, management practices and harvesting.
Figure 1. C. sativa: (a) whole plant, (b) inflorescence (flower), (c) seed, (d) leaf, (e) stem. Image source: Hourfane, Sohaib, Hicham Mechqoq, Abdellah Yassine Bekkali, João Miguel Rocha, and Noureddine El Aouad. 2023. “A Comprehensive Review on Cannabis sativa Ethnobotany, Phtoychemistry, Molecular Docking and Biological Activities.” Plants 12 (6): 1245. https://doi.org/10.3390/plants12061245.
Figure 1. C. sativa: (a) whole plant, (b) inflorescence (flower), (c) seed, (d) leaf, (e) stem. Image source: Hourfane, Sohaib, Hicham Mechqoq, Abdellah Yassine Bekkali, João Miguel Rocha, and Noureddine El Aouad. 2023. “A Comprehensive Review on Cannabis sativa Ethnobotany, Phtoychemistry, Molecular Docking and Biological Activities.” Plants 12 (6): 1245. https://doi.org/10.3390/plants12061245.
Stem
Cannabis can grow 1–6 meters tall, with a stem 1–3 centimeters in diameter. Stem height and diameter depend on the subspecies, environment and growing conditions.
The stem is green, hollow, cylindrical and longitudinally rigid and fluted. It is usually angular, furrowed and branched with a woody interior that can be hollow in the internodes.[2] Nodes are where older and new stems intersect and are key indicators of the sex of the plant because they are the sites of foliar leaves, bracts and pre-flowers.[3]
Leaves
As the primary photosynthetic organs, leaves play a crucial role in the physiology and growth of cannabis. Their morphology—including their size, shape and structure—directly influences the plant’s ability to capture light, exchange gases and regulate transpiration. Leaves are also often indicative of plant health, vigor and productivity because they’re tightly linked to physiological processes such as water and nutrient uptake, carbon assimilation and stress response.
The ubiquitous fan-shaped leaves of the cannabis plant are palmate with elongated segments and typically composed of 5–7 unequal lobes with serrated edges. The size and shape of the leaves, ranging in size from 6–11 cm in length and 2–15 mm in width, depend on genetics.
Leaf arrangement changes as cannabis grows. In the lower plant, leaves are arranged opposite each other, with two leaves on either side of the node. Moving up the plant, leaves start to alternate, with just one leaf per node (Figure 2).[4] The topmost leaves form the cola, where the largest flowers develop. Multiple colas can form at the budding sites below the main one. Both upper (adaxial) and lower (abaxial) leaf surfaces are green and covered in resinous trichomes.
Figure 2. Leaf arrangement in C. sativa. Image source: Hesami, Mohsen, Marco Pepe, Maxime de Rønne, et al. 2024. “Cannabis leaf arrangement: Transcriptome insights into Cannabis sativa phyllotactic regulation.” Plant Physiology Reports 29: 488-498. https://doi.org/10.1007/s40502-024-00801-8.
Figure 2. Leaf arrangement in C. sativa. Image source: Hesami, Mohsen, Marco Pepe, Maxime de Rønne, et al. 2024. “Cannabis leaf arrangement: Transcriptome insights into Cannabis sativa phyllotactic regulation.” Plant Physiology Reports 29: 488-498. https://doi.org/10.1007/s40502-024-00801-8.
Figure 3. C. sativa: (a–c) twigs with female inflorescences, (d) a twig of a male plant, (e) leaves showing variation in the number of lobes, (f) seeds. Image source: Raman, Vijayasankar, Hemant Late, Suman Chandra, Ikhlas A. Khan, and Mahmoud A. ElSohly. 2017. “Morpho-Anatomy of Marijuana (Cannabis sativa L.).” In Cannabis sativa L. – Botany and Biotechnology, edited by Suman Chandra, Hemant Lata, and Mahmoud A. ElSohly. Springer International Publishing.
Figure 3. C. sativa: (a–c) twigs with female inflorescences, (d) a twig of a male plant, (e) leaves showing variation in the number of lobes, (f) seeds. Image source: Raman, Vijayasankar, Hemant Late, Suman Chandra, Ikhlas A. Khan, and Mahmoud A. ElSohly. 2017. “Morpho-Anatomy of Marijuana (Cannabis sativa L.).” In Cannabis sativa L. – Botany and Biotechnology, edited by Suman Chandra, Hemant Lata, and Mahmoud A. ElSohly. Springer International Publishing.
Root system
Cannabis’ taproots penetrate up to 30 cm, with lateral roots extending 20–100 cm. In peaty soils, lateral roots are more developed, and the taproot is 10–20 cm long. The root system grows relatively slowly in the early vegetative phase compared to the rapid growth aboveground.[5]
Flowers
Cannabis grows long, slender flowers with glandular hairs that are fragrant and sticky. They are also the primary way to determine the sex of the plant:
- Female flowers are dark green and all but lack a flower stalk. They cluster closely together in pairs at the apex of inflorescences, mostly on the upper axes of branches. The ovary is encased in a calyx measuring 3–6 mm with two long, thin-feathered white, yellow or pink stigmas. A transparent perianth[6] covers nearly two-thirds of the flower when mature, and rough green bracts enclose it. Flower development at the apical regions of the main stem is shown in Figure 4.
- Male flowers are pale green and hang in flat-topped clusters called cymose panicles. A male flower has five tepals and as many stamens, as well as a thin pedicel (a small stalk). The yellowish or whitish green tepals are ovate and oblong, 2–4 cm long, with tiny hairs. The hanging stamens feature thin, oblong, greenish filaments and anthers, which release pollen.[7]
Figure 4. Female flower development of C. sativa: (a) central flower after 3 days, (b) 1 week, (c) 2 weeks, (d) 4 weeks, (e) 6 weeks and (f) 8 weeks. Image source: Hesami, Mohsen, Marco Pepe, and Andrew Maxwell Phineas Jones. 2023. “Morphological Characterization of Cannabis sativa L. Throughout Its Complete Life Cycle.” Plants 12 (20): 3646. https://doi.org/10.3390/plants12203646.[8]
Figure 4. Female flower development of C. sativa: (a) central flower after 3 days, (b) 1 week, (c) 2 weeks, (d) 4 weeks, (e) 6 weeks and (f) 8 weeks. Image source: Hesami, Mohsen, Marco Pepe, and Andrew Maxwell Phineas Jones. 2023. “Morphological Characterization of Cannabis sativa L. Throughout Its Complete Life Cycle.” Plants 12 (20): 3646. https://doi.org/10.3390/plants12203646.[8]
Trichomes
Trichomes are the tiny, hair-like structures on the surface of cannabis plants. They play a role in the biosynthesis and accumulation of bioactive compounds used in medicinal and recreational cannabis products, and their density, size and structure are directly related to the color, flavor, fragrance and potency or therapeutic effects of cannabis products. They also serve as defense mechanisms, acting as physical barriers and producing chemical compounds that deter pests.
Glandular trichomes are responsible for synthesizing and storing cannabinoids. Female plants produce higher levels of cannabinoids due to their dense concentration of glandular trichomes, while male and hermaphroditic plants, having less floral material, produce lower quantities of trichomes. Female plants have three types of glandular trichomes:[9]
- Bulbous trichomes are the smallest with 1- to 2-celled stalks and 1- to 4-celled heads. They vary in size but are usually 10–20 micrometers (µm) in diameter and 15–30 µm tall.
- Capitate-stalked trichomes have large globular heads that measure 50–70 µm in diameter and robust, multicellular stalks that are 100–200 µm wide, although their height is variable. High-THC strains have large glandular heads grow up to 119 µm.
- Capitate-sessile trichomes are most conspicuous in the early stages of bract development. Mainly found in the abaxial leaf surfaces, petioles and young stems, they have large globose heads roughly 30–50 µm in diameter. Although they appear to be stalkless, they have 1-cell high stalks that are 2–4 cells thick.
Figure 5. Microscopic photographs of C. sativa trichomes: (a) trichomes on the flower. (b) capitate-stalked trichome, (c) capitate-sessile trichome, (d) bulbous trichome, (e) trichomes on the bract, (f) trichomes on the stem, (g) trichomes on the adaxial surface of a floral leaf. A big capitate-sessile trichome is indicated with an arrow, and (h) trichomes on the abaxial surface of a leaf.[10]
Figure 5. Microscopic photographs of C. sativa trichomes: (a) trichomes on the flower. (b) capitate-stalked trichome, (c) capitate-sessile trichome, (d) bulbous trichome, (e) trichomes on the bract, (f) trichomes on the stem, (g) trichomes on the adaxial surface of a floral leaf. A big capitate-sessile trichome is indicated with an arrow, and (h) trichomes on the abaxial surface of a leaf.[10]
Conclusion
Cannabis sativa is a complex taxon with variable morphological features. Understanding these features helps growers to distinguish between strains, recognize the phases of the cannabis crop cycle, and assess the health of the plant. This knowledge not only informs cultivation practices but also aids growers in choosing the right cultivar.[11] And by monitoring plant development, growers can address issues that arise and optimize growing conditions.
Emerald Harvest Team
[1] In contrast, plant anatomy refers both to the scientific study of the internal physical structure of plants, particularly at the cellular level, and to the descriptive terminology used to characterize these traits.
[2] An internode is the part between two nodes.
[3] Raman, Vijayasankar, Hemant Late, Suman Chandra, Ikhlas A. Khan, and Mahmoud A. ElSohly. 2017. “Morpho-Anatomy of Marijuana (Cannabis sativa L.).” In Cannabis sativa L. – Botany and Biotechnology, edited by Suman Chandra, Hemant Lata, and Mahmoud A. ElSohly. Springer International Publishing.
[4] Raman, Vijayasankar, Hemant Late, Suman Chandra, Ikhlas A. Khan, and Mahmoud A. ElSohly. 2017. “Morpho-Anatomy of Marijuana (Cannabis sativa L.).” In Cannabis sativa L. – Botany and Biotechnology, edited by Suman Chandra, Hemant Lata, and Mahmoud A. ElSohly. Springer International Publishing.
[5] Hourfane, Sohaib, Hicham Mechqoq, Abdellah Yassine Bekkali, João Miguel Rocha, and Noureddine El Aouad. 2023. “A Comprehensive Review on Cannabis sativa Ethnobotany, Phtoychemistry, Molecular Docking and Biological Activities.” Plants 12 (6): 1245. https://doi.org/10.3390/plants12061245
[6] The outer part of a flower, composed of the calyx and the corolla (petals).
[7] Barcaccia, Gianni, Fabio Palumbo, Francesco Scariolo, Alessandro Vannozzi, Marcello Borin, and Stefano Bona. 2020. “Potentials and Challenges of Genomics for Breeding Cannabis Cultivars.” Frontiers in Plant Science 11: 573299. https://doi.org/10.3389/fpls.2020.573299.
[8] Hesami, M., Pepe, M., & Jones, A. M. P. (2023). Morphological Characterization of Cannabis sativa L. Throughout Its Complete Life Cycle. Plants (Basel, Switzerland), 12(20), 3646. https://doi.org/10.3390/plants12203646
[9] Raman, Vijayasankar, Hemant Late, Suman Chandra, Ikhlas A. Khan, and Mahmoud A. ElSohly. 2017. “Morpho-Anatomy of Marijuana (Cannabis sativa L.).” In Cannabis sativa L. – Botany and Biotechnology, edited by Suman Chandra, Hemant Lata, and Mahmoud A. ElSohly. Springer International Publishing.
[10] Farag, Sayed and Oliver Kayser. 2017. “Chapter 1 – The Cannabis Plant: Botanical Aspects.” In Handbook of Cannabis and Related Pathologies, edited by V.R. Preedy. Academic Press.
[11] Hesami, Mohsen, Marco Pepe, and Andrew Maxwell Phineas Jones. 2023. “Morphological Characterization of Cannabis sativa L. Throughout Its Complete Life Cycle.” Plants (Basel) 12 (20): 3646. https://doi.org/10.3390/plants12203646.
