Pancratium maritimum -- California

Pancratium maritimum has naturalized in California, the Azores, and Bermuda. It is also recorded from several other locations in the United States (e.g., Tennessee, Mississippi, Louisiana), with occurrences outside of gardens or cultivation and potentially naturalized. The first herbarium collection record in the wild in California was from El Segundo Dunes, in 1987, where the species apparently still persists. Since then it has been observed to be spreading locally in coastal dune habitat in Ventura County. It is native to the Mediterranean coastline of Eurasia and northern Africa, as well as the Atlantic coastline of Spain, the Canary Islands, and the Black Sea. Pancratium maritimum is considered a sensitive species in parts of its range, where open sand dune habitat is being lost through development.

Pancratium maritimum has naturalized in California. The first herbarium collection from the wild in California was from El Segundo Dunes in 1987 and it has since been well documented as persisting and reproducing locally in Ventura County coastal dune habitat. To date (2023), southern California is the only region worldwide where it has naturalized in a climate that matches the climate of California (see Climate Match map for California).

I could not find any reports of Pancratium maritimum's status as an invasive plant in the U.S. or world. It is considered problematic in the coastal dunes of Ventura, CA (J. Beall, pers. comm.) and has naturalized in the Azores and the Bahamas.

I could not find any formal designation of Pancratium maritimum's status as an invasive plant in areas with climates similar to California. Randall (2017) does not list it as being invasive in any region and gives it a low global ranking for invasiveness. However, it is considered problematic in the coastal dunes of Ventura, CA (J. Beall, pers. comm.).

Other species of Pancratium appear to be less common than P. maritimum and none appear to have been identified as being invasive.

The native range of Pancratium maritimum (Mediterranean coastal region of Europe, western Asia, and north Africa, as well as Atlantic coast of southern Europe) largely matches the climate of California. Overall, more than half of its distribution overlaps with areas matching California's climate, especially when areas of highest abundance are considered (see Climate Match map and GBIF).

This species occurs as sparsely distributed clumps in coastal sand dunes and is not described as a species that forms dense monocultures that overtop other species. Pancratium maritimum is also relatively low in stature (

The presence of seasonal leaves and low stature, in addition to its preferred habitat of active sand dunes with low vegetation cover strongly suggest that Pancratium maritimum does not alter fire regimes.

All species in the Amaryllidaceae produce alkaloids that have cytotoxic effects, and Pancratium maritimum is no exception. The bulb is considered toxic to humans, though alkaloids that it produces are also being studied for their anti-cancer and other medicinal properties. A mild toxic response was found in rats in feeding trials (Davo 2021). Pancratium and many other Amaryllidaceae are toxic to most generalist insects, a trait that may facilitate their spread in environments where they are not native. Zahreddine et al. (2004) report that high abundance of Pancratium maritimum at two sites within its native range is likely a result of rabbits being introduced and removing competing vegetation, but avoiding the species. The authors also mention a local report of the odor of Pancratium's flowers being so intense and apparently distasteful to sheep that they avoided a site with these plants. This inferred impact on a "grazing systems" supports the answer of "yes" with "medium" confidence. This species is not likely to directly cause poisoning in humans, livestock, or wildlife because the opportunity for exposure and ingestion is so low in the field.

This species occurs as sparse colonies coastal sand dunes. I could find no reports of Pancratium maritimum forming dense thickets. It is also relatively low in stature (

Paradiso et al. (2009) report that the production of bulblets is a common form of clone expansion, though the rate of reproduction via bulblets is slow, with only 1-3 bulblets produced per bulb in a 2-year period. Zahreddine et al. (2004) quantified the number of bulbs per clump compared to number of clumps within populations and, based on high numbers of bulbs per clump concluded that a subset of populations studied had extensive vegetative propagation.

While bulbs produce bulblets and can expand locally as clones in this manner, vegetative propagation is not the primary method of reproduction and spread. Bulblets are produced on deeply rooted bulbs (often over 50cm below the soil/sand surface) and therefore do not have means to detach and disperse. Reproduction by seed, in contrast, has commonly been observed.

Numerous authors have conducted studies on seed production and propagation of this species. Flowers typically produce around up to 20 mature seeds/capsule, though the number of ovules is over 50 in each ovary. High germination rates also indicate high seed viability. Pancratium maritimum is considered to be self compatible based on population genetic data (Zahreddine et al., 2004; Medrano et al, 2000).

Based on the various estimates of seed and flower production by different authors, individual Pancratium maritimum plants are not capable of producing more than 1000 seeds/plant. Maximum flower number per plant has been reported as 13 in at least one study, and number of seed per fruit appears to only rarely exceed 20. Therefore, a generous estimate of seed production per plant (bulb) would be 260.

Numerous studies have been conducted on germination patterns of Pancratium maritimum. All report high germination rates (up to 95%) without seed treatment. Grassi et al. (2005) report a bimodal germination pattern within a single germination season (winter). Balestri and Cinelli (2004) reported only 18% of seed remained ungerminated after a germination trial without treatment. Once germinated, seedlings are, however, highly vulnerable to desiccation in non-optimal conditions (Balestri and Cinelli, 2004). Germination success is higher when seeds are buried more deeply.

Paradiso et al. (2009) report that Pancratium maritimum typically requires five years from germination to flower.

Multiple studies have reported a flowering period of over three months (from June through September) for Pancratium maritimum. Individual flower stems flower within a shorter timeframe.

The primary modes of dispersal for Pancratium maritimum appear to be wind and water. Grassi et al. (2005) make reference to the possibility of bird dispersal but do not provide any evidence for their claim beyond the likely nutritional value of seeds.

DiCastro et al., (2020) and others have provided a linkage between the genetic composition of Pancratium maritimum populations and water current patterns. Werker and Fahn (2005) showed that seeds could both float and stay viable after over two weeks in saltwater due to aerenchyma and other specialized seed anatomy, though flushing with fresh water was required to stimulate germination. Balistri and Cinelli (2005) reported that saltwater inhibited germination. The distribution of Pancratium maritimum across widely dispersed coastal dune sites also supports movement of seed by water.

I found no evidence of human dispersal via contaminated seed or equipment. Most likely its dispersal to distant new locations is a result either of ornamental introduction or of long-distance dispersal by sea. Fruits are dry and dehiscent upon maturity. In contrast to at least one congener, the seeds of P. maritimum do not have eliasomes; they do contain "two or three compressed outer layers of cells of the testa..." and "large, dead, air-fi]led cells with large inter- cellular spaces between them." (Werker and Fahn, 1975)