''Lessingia arachnoidea'' is a rare species of flowering plant in the family

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

known by the common name Crystal Springs lessingia. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to the U.S. state of

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

, where it is known from a few occurrences in the vicinity of

Crystal Springs Reservoir Crystal Springs Reservoir is a pair of artificial lakes located in the northern Santa Cruz Mountains of San Mateo County, California situated in the rift valley created by the San Andreas Fault just to the west of the cities of San Mateo and H ...

on the San Francisco Peninsula and southward to serpentine soil in Woodside. It may also exist in Sonoma County to the north. The plant grows in

chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterranean c ...

, scrub, grasslands and other local plant communities, on

serpentine soil Serpentine soil is an uncommon soil type produced by weathered ultramafic rock such as peridotite and its metamorphic derivatives such as serpentinite. More precisely, serpentine soil contains minerals of the serpentine subgroup, especially anti ...

s. This is an annual herb producing a slender, erect stem up to 80 centimeters in maximum height. It is woolly toward the ends of the stems, less so toward the base of the plant. The leaves are narrow and sometimes toothed, the lowest approaching 11 centimeters long and the uppermost reduced in size. The

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed o ...

is made up of a single flower head at the tip of the slender stem. The flower head is lined with tiny lance-shaped phyllaries with purplish pointed tips and sometimes a coat of woolly fibers. The head is discoid, lacking ray florets but bearing several funnel-shaped lavender disc florets with raylike lobes. The fruit is an

achene An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not ope ...

with a very hairy hard body 2 or 3 millimeters long and a small, bristly pappus on top. Plants need bare soil or soil without any exotic weed competition to thrive, and can even grow in the bare soil of well worn trails. Late-flowering from August to October, and one of the last of the summer California wildflowers to bloom. Plants are able to grow without any rainfall or any moisture in the ground around their roots, surviving by absorbing dewfall at night through their leaves. Ripe seeds germinate readily, 40% in three days and 80% within 15 days. When managing or restoring this species, the estimated longevity of seeds in the soil is between 100 and 250 years. Even though these plants live in serpentine soil which is known to be low in nutrients, however, these plants still require a minimum threshold of nitrogen, phosphorus, potassium, calcium, magnesium, copper, zinc, manganese, iron and boron and a narrow range of pH for their seedling's survival and to grow to adults and reproduce. The pH is 7.1 and the PPM thresholds for nutrients are: N = 18, P = 5, K = 31, Ca = 391, Mg = 256, Cu = 1, Zn = 1, Fe = 26, and B = 0.02 PPM.Dremann, Craig Carlton. 2022 Waypoint Lab Anaheim, CA A-01 Soil Test Report 22-124-001, Data only in bar graph format of a one-quart sample taken from the top two inches and sifted through 1/4 inch mesh screen to remove rocks and vegetable material. Unpublished.

References

External links

Jepson Manual TreatmentUSDA Plants ProfilePhoto gallery
{{Taxonbar, from=Q6531693 arachnoidea Endemic flora of California Plants described in 1910