Cycas circinalis L. is the plant that started it all — the first cycad ever described in Western science, the type species of the genus Cycas, and one of the most historically important yet most misunderstood plants in the entire order Cycadales. Known as the queen sago, it was illustrated in Rheede’s Hortus Malabaricus in 1682 under the Malayalam name todda panna, formally named by Linnaeus in 1753, and then subjected to 250 years of taxonomic confusion during which its name was applied — incorrectly — to virtually every large tropical cycad from Indonesia to Guam to East Africa.
Today, thanks largely to the work of K.D. Hill (1994, 2004), Cycas circinalis sensu stricto is understood to be an Indian endemic, restricted to the Western Ghats of Kerala, Karnataka, Tamil Nadu, and southern Maharashtra. The plants previously called “Cycas circinalis” in Indonesia are now recognised as Cycas rumphii; those from Madagascar and East Africa as Cycas thouarsii; those from the Philippines as Cycas riuminiana; and the infamous “cycas of Guam” as Cycas micronesica. Any reader consulting pre-1994 literature on Cycas circinalis must be aware that the name may refer to any of these species.
Taxonomy and nomenclature
Described by Linnaeus in Species Plantarum (1753), based primarily on Rheede’s illustration in Hortus Malabaricus (1682). The lectotype was formally designated by Jarvis et al. in 1993. Family Cycadaceae, order Cycadales. The epithet circinalis derives from the Latin circinus (a spiral or compass), referring to the circinate (coiled) vernation of the emerging fronds — a trait shared by all cycads but particularly conspicuous in this large-leaved species.
Cycas circinalis belongs to subsection Rumphiae within the genus — the “buoyant-seeded” clade whose members share a spongy endotesta that allows seeds to float on seawater, a unique adaptation within Cycas. However, whereas Cycas rumphii and Cycas thouarsii have evidently used ocean dispersal to colonise vast island archipelagos, Cycas circinalis is confined to inland hillsides in southern India, far from the sea — a biogeographic puzzle that suggests the species may have occupied coastal habitats in the past.
Synonyms and misapplications
The synonymy of Cycas circinalis is enormous and reflects its centuries-long role as a “wastebasket” name. Important synonyms include Cycas undulata Desf., Cycas wallichii Miq., and Cycas squarrosa Lodd. Previous subspecies now treated as separate species include Cycas circinalis subsp. riuminiana (= Cycas riuminiana, Philippines) and Cycas circinalis subsp. thouarsii (= Cycas thouarsii, Madagascar/Africa).
Common names
Queen sago, queen sago palm (English); todda panna (Malayalam, from Rheede 1682); mundicalu (Kannada); canningay (Tamil).
Morphological description
Habit and caudex
A large, arborescent, dioecious evergreen gymnosperm. The caudex is stout, erect, reaching 3–5 m (sometimes higher) in the wild, with a diameter of 20–35 cm. The trunk surface is rough, covered in persistent leaf bases that create a distinctive textured pattern — Haynes (2004) notes that this surface is “sometimes used by growers to mount epiphytic orchids.” The crown of mature specimens is broad and open, with long, gracefully arching fronds creating a canopy wider and more spreading than the compact, tight globe of Cycas revoluta.
Leaves
Leaves are among the largest in the genus: pinnate, 150–250 cm long, flat in cross-section (the opposing leaflets are inserted at approximately 180° on the rachis — flat, not V-shaped). Leaflets number approximately 170 per frond, up to 25 cm long and 10–13 mm wide (notably narrower than those of Cycas rumphii), bright green, semi-glossy, with flat margins (not revolute as in Cycas revoluta). The petiole is armed with spines along its lower half. Tomentum (fuzzy hairs) is shed as the leaf expands. The overall impression is of a large, graceful, palm-like crown — more open and tropical-looking than the stiff, compact rosette of Cycas revoluta.
Importantly, Cycas circinalis is facultatively deciduous — in the dry season of its native Western Ghats habitat, where the monsoon creates a pronounced alternation between wet and dry periods, the plant may drop its fronds entirely. This is unique among commonly cultivated Cycas species and reflects its adaptation to the seasonally dry tropical forests of southern India.
Reproductive structures
Male cones are large, egg-shaped to conical, 34–48 cm long and 12–18 cm wide, yellowish-brown. Microsporophyll apices are attenuate (tapering) and reflexed — a diagnostic character. Female megasporophylls are non-pectinate (without a comb-like fringe), with a relatively large, broadly rhomboid lamina — this is the key character distinguishing Cycas circinalis from Cycas rumphii and Cycas thouarsii, whose megasporophylls are narrower and more deeply toothed.
Seeds
Seeds are relatively small for the subsection: subglobular to elongated, 30–39 mm long and 20–24 mm wide, light yellow to reddish-brown at maturity. The sarcotesta contains a distinctive spongy, fibrous layer that makes the seeds buoyant — they float in water when viable. This trait is shared with Cycas rumphii and Cycas thouarsii but is absent from all other Cycas sections. Cycas circinalis produces the largest ovules in the plant kingdom — up to 6 cm long before seed maturation.
Distribution and natural habitat
Cycas circinalis is endemic to the Western Ghats of southern India, occurring in the states of Kerala, Karnataka, Tamil Nadu, and southern Maharashtra. It grows in fairly dense, seasonally dry scrubby woodlands on hilly terrain, from low elevations to approximately 1,000 m. The vegetation is typically semi-deciduous to deciduous monsoon forest, with many associated tree species shedding their leaves during the pronounced dry season (November–May).
Climate in the natural range
The Western Ghats experience a strongly monsoonal climate. Rainfall during the south-west monsoon (June–September) can exceed 2,000–3,000 mm, while the dry season (November–May) may see virtually no rain. Temperatures in the cycad’s elevational range are warm year-round, with mean annual temperatures of 24–28 °C and minima rarely if ever reaching frost. This is an entirely tropical species with no natural frost exposure — a critical point for cultivation, as it is significantly less cold-hardy than the temperate-origin species Cycas revoluta, Cycas panzhihuaensis, or Cycas taitungensis.
Conservation status
IUCN Red List: Endangered (EN). The species faces significant threats from habitat loss (deforestation, agricultural encroachment in the Western Ghats), collection for traditional medicine and ornamental use, and the growing threat of Aulacaspis yasumatsui where it has been introduced in cultivation. The Western Ghats are a UNESCO World Heritage site and a global biodiversity hotspot, but fragmentation of forest habitat continues. All Cycas species are listed in CITES Appendix II.
Cultivation guide
| Hardiness | Frost-tender; minimum approximately 2–5 °C (USDA zone 10a–11) |
| Light | Full sun to partial shade; tolerates dappled shade in tropical settings |
| Soil | Well-drained but moisture-retentive; slightly acidic to neutral |
| Water | Moderate; tolerates seasonal drought (facultatively deciduous) |
| Growth rate | Moderate for a cycad |
| Mature size | 3–5 m typical; to 8 m in the wild over centuries |
Key cultivation point: this is a tropical species
Unlike Cycas revoluta, which tolerates frost to −8/−10 °C, Cycas circinalis is a tropical plant that does not tolerate frost. It is suitable for outdoor cultivation only in USDA zones 10a–11 (minimum 2–5 °C). In subtropical and warm-temperate regions (zones 9a–9b), it can be grown outdoors in sheltered, frost-free microclimates or in containers that are brought under cover in winter. It is widely cultivated in Hawaii, southern Florida, and tropical botanical gardens worldwide.
The species’ tolerance of seasonal drought (dropping fronds during dry spells) is an asset in Mediterranean-type climates, where summer drought occurs naturally — but winter cold remains the limiting factor. In the right climate, Cycas circinalis is a fast and satisfying grower, producing large, impressive fronds that exceed those of Cycas revoluta in both length and number of leaflets.
Landscape use
An outstanding specimen for tropical and subtropical landscapes. The broad, open crown and long, arching fronds create a powerful architectural effect — more “tropical palm” than the compact, formal look of Cycas revoluta. In Hawaii, it is widely used both as a landscape plant and for cut foliage. The textured trunk can serve as a platform for mounting epiphytic orchids and ferns.
Propagation
Seed: Clean the sarcotesta (wearing gloves), soak 24–48 hours, plant half-buried at 25–30 °C. Germination typically within 2–4 months. Seeds are buoyant (they float), which can be used to test viability — floating seeds are more likely to be viable.
Offsets: Basal offsets develop on mature plants and can be separated and rooted.
Pests and diseases
Aulacaspis yasumatsui is the primary threat in cultivation. The same pest has reached natural cycad populations in several regions. Root rot from waterlogging is a concern in poorly drained soils. Weevil pollination — a mutualistic relationship between the cycad and specific beetle pollinators — is well documented for this species.
Toxicity and the Guam confusion
All parts of Cycas circinalis contain cycasin and BMAA. In Kerala and other parts of southern India, the seed endosperm has been traditionally processed into starch (a famine food) through repeated soaking and washing to leach out the water-soluble toxins. This practice carries significant health risks, and chronic consumption has been linked to neurological symptoms.
The famous “cycad hypothesis” for the ALS-parkinsonism-dementia complex (ALS-PDC, or lytico-bodig) on Guam — which implicated cycad flour consumption and BMAA biomagnification through flying foxes — was originally attributed to Cycas circinalis because that was the name applied to the Guam cycad at the time (Vega & Bell 1967, Whiting 1963). The Guam cycad was subsequently reclassified as Cycas micronesica K.D.Hill (1994), a species in the Cycas rumphii complex. True Cycas circinalis does not occur on Guam and has no connection to the Guam disease cluster. Any reference to “Cycas circinalis” in the BMAA/ALS-PDC literature refers to the plant now known as Cycas micronesica.
Comparison: Cycas circinalis vs Cycas rumphii vs Cycas thouarsii
| Character | Cycas circinalis | Cycas rumphii | Cycas thouarsii |
|---|---|---|---|
| Distribution | S. India (Western Ghats) only | Indonesia, New Guinea, Christmas Is. | Madagascar, Comoros, Seychelles, E. Africa coast |
| Leaflet width | Narrow (≤13 mm) | Broad, falcate, glossy | Medium (~17 mm), lanceolate |
| Megasporophyll lamina | Broadly rhomboid, non-pectinate, large | Narrowly triangular, slender apical spine | Ovate-lanceolate, with 12–16 short lateral spines |
| New leaf colour | Green | Green | Distinctly bluish — diagnostic |
| Seed size | 30–39 mm | 40–52 mm | 50–60 mm (largest in genus) |
| Seeds float? | Yes (spongy endotesta) | Yes (spongy endotesta) | Yes (spongy endocarpe) |
| Cold hardiness | Frost-tender (zone 10a+) | Frost-tender (zone 10a+) | Frost-tender (zone 10a+) |
| IUCN status | Endangered (EN) | Near Threatened (NT) | Least Concern (LC) |
Authority websites
POWO — Plants of the World Online (Kew): https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:297015-1
IUCN Red List — Cycas circinalis: https://www.iucnredlist.org/species/42078/2950580
The Cycad Pages (K.D. Hill, Royal Botanic Gardens Sydney): https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/cycadpg?taxname=Cycas+circinalis
LLIFLE — Encyclopedia of Living Forms: https://www.llifle.com/Encyclopedia/PALMS_AND_CYCADS/Family/Cycadaceae/28817/Cycas_circinalis
National Tropical Botanical Garden (NTBG): https://ntbg.org/database/plants/detail/Cycas-circinalis
India Biodiversity Portal: https://indiabiodiversity.org/species/show/242939
The World List of Cycads: https://cycadlist.org/
Bibliography
Linnaeus, C. (1753). Species Plantarum, Vol. II, p. 1188. Original description of Cycas circinalis.
Rheede, H. van (1682). Hortus Malabaricus, Vol. III, pp. 9–21, tabs. 13–21. First Western illustration of the species as “Todda Panna.”
Hill, K.D. (1994). The Cycas rumphii complex (Cycadaceae) in New Guinea and the western Pacific. Australian Systematic Botany, 7(5), 543–567.
Hill, K.D. (2004). The genus Cycas (Cycadaceae) in India. Indian Journal of Botany.
Whitelock, L.M. (2002). The Cycads. Timber Press, Portland, Oregon.
Jarvis, C.E. et al. (1993). Lectotypification of Cycas circinalis L.
de Laubenfels, D.J. & Adema, F. (1998). A taxonomic revision of the genera Cycas and Epicycas gen. nov. (Cycadaceae). Blumea, 43, 351–400.
Last updated: March 2026