Nuttall’s Lotus

Nuttall’s lotus (Acmispon prostratus) is a plant of coastal dunes – a low sprawling plant that hugs the ground as if to keep the sand beneath from blowing away. The flowers are small, but showy, with bright yellow petals streaked and spotted with clear red.

Nuttall’s lotus is native to a slender strip of coastal strand habitat between Oceanside and northern Baja California. This habitat is seriously threatened by encroaching development, recreational activities and military use. As a consequence Nuttall’s lotus is one of several sand dune plants that are facing extirpation in San Diego County.

A small population of Nuttall’s lotus survives in the West Basin of San Elijo Lagoon, between the railroad tracks and Coast Highway. If you drive Coast Highway regularly, you may have have noticed a fence enclosing four acres just east of the road where it crosses San Elijo Lagoon. This marks an on-going restoration project of Nature Collective to protect and enhance the dune habitat for sand-loving species such as Nuttall’s lotus, legless lizards, snowy plovers and least terns.

Description ^2,8,468

Nuttall’s lotus is a ground-hugging annual plant. Several wiry, green to brown stems extend up to a meter in length from a central taproot. One plant may spread out in a lacy circle or several plants may be crowded into a mat. Stems and leaves are hairless or covered with short, stiff whitish hairs. The slightly thickened, waxy leaves are pinnately divided with three – six obovate leaflets; leaflets are gray-green and may have a reddish margin; leaflets are usually less than 7/16 inch (1.2 cm) and about half as wide

Flowers are produced in clusters of 3-8 on long flower stalks toward the ends of the stems. The calyx is much shorter than the petals. Flowers are yellow often flushed red. They have the bilateral shape of a typical pea flower.¹⁴³ The upper petal is large, flaring upward forming the “banner”. Two side petals (“wings”) are directed forward, partially enclosing the remaining two petals which are fused lengthwise into a “keel”. The tip of the keel bears a red spot, which is in the right position to serve as a landing beacon for pollinators. The keel encloses a single pistil and ten stamens, nine united and one free. Unlike flowers of the similar deerweed (A. glaber) petals are not retained after fertilization. The main bloom period is March-June.^1,7

The fruit is a slender two-seeded pod 5/8 inch (1-1.5 cm) long, tapering to a terminal beak. The pod does not open to release the seeds.

Classification ^2,44,143

Nuttall’s lotus is a dicot angiosperm in the pea or legume family (Fabaceae; previously called Leguminosae). Members of this family are characterized by their fruit, which is an elongated pod with seeds attached along one seam and which usually opens along the opposite seam. Most members of this family have a flower similar to a pea or sweet pea flower. Many members have compound leaves, and many members have nitrogen-fixing bacteria in specialized root nodules.¹¹

The pea family is the third largest family of angiosperms in the world and one of the most economically important, often associated with developing societies. In addition to peas and beans, the pea family includes peanuts, licorice, acacia, and clover. Other members of this family found commonly in the Reserve include ocean locoweed (Astragalus trichopodus), collar lupine (Lupinus truncata) and chaparral sweet pea (Lathyrus latiflorus).

Species of the genus Acmispon were formerly placed in the genus Lotus, a world-wide genus that has been in taxonomic flux for many years. Recent DNA analysis has lead taxonomists to move all the new world species into two different genera, Hosackia and Acmispon.^59,171 There are six species of Acmispon reported from the Reserve;⁴⁸ the most common is Deerweed (A. glabra).

Ecology ^165,167

The coastal strand habitat of the upper beach and dunes is one of the harshest environments on earth. Like the handful of other species that thrive in these alternately wet, salty, hot, dry, wind-swept conditions, Nuttall’s lotus has specific adaptations for survival. A sturdy taproot anchors the plant in the wind, while long, low, spreading branches keep the sand from blowing out from under it. The small, thickened, waxy leaves retard water loss, and small white surface hairs reflect the hot, drying sun. Root nodules shelter nitrogen-fixing bacteria that provide nitrogen in the nutrient-impoverished soil. Nuttall’s lotus is an annual, which is unusual among dune plants but allows it to survive the hottest and driest days of summer as a seed.

Human Uses  

We are searching for information about past or present uses of Nuttall’s lotus. If you can help, please send information to; plant-guide@thenaturecollective.org

Interesting Facts ⁴⁵

The persistence of Nuttall’s lotus is seriously threatened by loss of the coastal strand habitat to which it is adapted. San Elijo Lagoon’s West Basin is one of only 26 populations known to exist in California.¹¹³ In an effort to protect Nuttall’s lotus and several other strand species, four acres of coastal strand habitat have been fenced off and invasive species removed. Recovery of native species is being closely monitored.

Several organizations have classification systems for rare or threatened species. We use the system of the California Native Plant Society (CNPS) that classifies Nuttall’s lotus as 1B.1. What exactly does this mean?

The first number, here = 1, means the plant is considered rare, threatened or endangered in California and throughout its range. Other possible categories are: 2 – species is rare in California but more common elsewhere, 3 – more information is needed before the species can be assigned (or not assigned) to rank and 4 – species has limited distribution or is locally infrequent with has the potential for future declines; deserves continued monitoring.

The letter, here = B, means populations still exist in California. The other possible category, “A”, indicates the species has been extirpated in California. Since 1994, 13 species in the “A” category have been rediscovered by sharp-eyed botanists.

The last number, here = 1, indicates the level of endangerment in California, with 1 being the highest and 3 the lowest.

Thus a CNPS rank of 1B.1 is the most critical ranking a species can achieve in California without going extinct!