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 and animals that are facing extirpation in San Diego County.

The need to protect this vanishing habitat lead the Nature Collective to undertake a series of restoration projects in the West Basin of San Elijo Lagoon and along Cardiff State Beach, culminating in the establishment of the Cardiff Living shoreline in 2019. Nuttall’s lotus and several other endangered species, from coast woolly heads to legless lizards to snowy plovers, now thrive in a secure habitat.

Description ^2,4,8,468

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 1/2 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 related 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 (Acmispon protratus) 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; one exception are the Acmispon, which have pods that do not open to dispense seeds. Most members of the pea 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. 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. Plants must survive alternately wet, salty, hot, dry and wind-swept conditions, and, like the handful of other species that thrive here, Nuttall’s lotus has specific adaptations.  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. In addition, Nuttall’s lotus has root nodules that shelter nitrogen-fixing bacteria; these 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 California Native Plant Society (CNPS) 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 to rank and 4 – species has limited distribution or is locally infrequent with 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!