Plants of Southern California: Interesting Facts

This page is a home for some of the interesting facts that we come across for some of the species in Southern California. This page was just begun on 9/24/03, so it will be a while before it contains much information.

Table of Contents

Plant Distribution
Plant Properties
Other Facts

Plant Distribution

Most Common Chaparral Species in California: Adenostoma fasciculatum, chamise. From Botanical And Ecological Characteristics:

Chamise is the most common chaparral species throughout the foothills and coastal mountains of California [13,38,39]. It is present in approximately 70 percent of California chaparral [13,39]. It is most often associated with hot, xeric sites [43] over a wide range of elevations, soils, latitudes, and distances from the coast [44]. In southern California it is a ubiquitous dominant on outwash plains, mesas, ridges, and dry, south- and west-facing slopes at elevations up to 6,000 feet (1,800 m) [18,35,38,52,91,100,121]. Sites supporting chamise commonly receive between 10 and 40 inches (250 and 1,000 mm) of annual precipitation, and have a temperature range from 32 to 100 degrees Fahrenheit (0-38 deg C) [48].

Most Widely-Distributed Tree in North America: Populus tremuloides, Quaking Aspen (Silvics of North America: Quaking Aspen, USDA Forest Service Agriculture Handbook 654, 1990. "Worldwide, only Populus tremula, European aspen, and Pinus sylvestris, Scotch pine, have wider natural ranges."

Perhaps most widely distributed of all vascular seed plants: Phragmites australis. (JM, p. 1282)

World-wide Species Showing Founder Effect: Xanthium strumarium. A founder effect is a local morphological variation caused when colonies form from a small number of individuals which have only a restricted set of the genes found in the entire population. (Wayne Armstrong's Genetic Drift: The Founder Effect)

California species with greatest distance to its nearest relatives:

Rarity of Plant Species: for Eriogonum of North America: About a third of the species are uncommon to rare in their distribution.
Source: James Reveal,, accessed 9/13/2003.
This seems to be true in general. See How Common Are The Plants Of Southern California?

Species never abundant anywhere: Asclepias albicans, said to be never abundant by Morhardt and Morhardt (2004). (We'll add other species as we come across them.)

It is a complete mystery to us why some species are only found in widely-separated single or small number of plants. We would have thought this to be nearly impossible to achieve in a steady-state. How do these species reproduce, and if their seeds can be so far-flung, why do they succeed in such few locations?

Number of Species Known In 2004 To Have Gone Extinct In California: 29. (UC Davis Magazine Online, 20: No. 4.)

World's Worst Weed: "often considered" to be Cyperus rotundus, purple nutsedge (JM, p. 1139). It occurs as a weed in 100 countries, and was picked as the worst weed in the book The World's Worst Weeds, Holm et al., 1977. That book details 18 of the world's most serious agricultural weeds and 73 other troublesome weeds.

However, a potent weapon is available to pursue every last tuber of purple nutsedge: pigs!

Other votes from around the world for species listed on at least two webpages as the World's Worst Weed (presented here just for fun, since this criterion is not nearly as scientific as the survey from Holm et al):

Interestingly, none of these are problem weeds in undisturbed areas of Southern California, primarily because they are weeds of wet places. The only occurrence we have of any of these species is a single flora, the Santa Monica Mountains, that contains Cyperus rotundus. In that flora, it is said to be a rare weed about plantings, vicinity of Santa Monica. However, it apparently does cause serious crop losses in irrigated areas of Southern California.

Southern California's Worst Weed: We haven't found any definitive statement on the matter for all of Southern California.

Some wetland candidates, taken from a meticulous mapping of 438 acres of wetland habitat by Brad Burkhart and Mike Kelly in 2002 (Burkhart and Kelly 2005, Ecological Restoration, 23:1, 40):

  1. Arundo donax, giant reed. This plant completely takes over riparian habitats, and would have to be on anyone's list of these weeds. It was by far the worst weed, accounting for 58% of the area covered by weeds.
  2. Schinus terebinthifolius, Brazilian pepper tree, 10% of the weed coverage area.
  3. Eucalyptus spp., also 10% of the weed coverage area

The specific area surveyed was 11.5 miles along the San Diego River within the city limits of San Diego, excluding Mission Trails Regional Park. Invasive weeds covered a total of 66 acres, 15% of the total area.

There are many other invasive weeds that cover a significant percentage of the natural areas of Southern California. If any reader knows of anyone who has proposed any of them as a candidate for the Worst Weed, let us know.

Native Southern California Species That Are Weeds Elsewhere:

Species That We Can't Figure Out Whether They Are Native or Not::

SpeciesMunzJepson ManualFlora of North America2005 Western Riverside County Flora
Bromus triniiNativeNon-Native; "probably native to w S. America"(Poaceae not published yet)Native
Galium aparine"said to be introduced"Native; "perhaps non-native"(Rubiaceae not published yet)Non-native
Solanum americanumNon-nativeNative; "may be early introduction"(Solanaceae not published yet)Non-native

It is hard to believe that in the 21st century we still can't say for sure whether the above species are native to California or introduced to California by humans in historic time. DNA testing should definitively reveal how long ago the populations in California diverged from the populations elsewhere, since all we need to know is whether they diverged less than 500 years ago or more than tens of thousands of years ago. In fact, even good old morphological and hybrid studies were able to show that the disjunct populations of Senecio mohavensis between Southern California and southwest Asia were native in both places and not human introductions (Coleman, Forbes and Abbott 2001, Edinburgh Journal of Botany 58: 389-403).

World-wide taxa like Xanthium strumarium (see above) possibly also belong in this category, since there is still debate at times whether some of these species were introduced in some areas by humans.

There is a similar class of plants, such as Gnaphalium straminium / G. chilense, which are in genera thought to be native to both southwest North America and west-central South America but which show evidence of genetic exchange between the two places on a longer time scale than the human-introduction time scale of a few hundreds of years. DNA studies have clarified their relationships in some cases, showing that deducing whether the above species are introduced or not should be a piece of cake.

For example:

Two examples of this latter case which are considered to be native in the California floras listed above, and to be introduced to central Chile are:

Plant Properties

The World's Largest Plant by Mass: a "single clone of aspen (Populus tremuloides) with 47,000 stems connected below ground, and covering more than 42 ha (Grant 1993)", quoted from Plants and Vegetation, Keddy 2007, p. 141.

Clones of bracken fern, Pteridium aquilinum, "may exceed 1000 m in diameter (Parks and Werth 1993)", quoted from Plants and Vegetation, Keddy 2007, p. 141.

The World's Largest Individual Plant Flower: the "Stinking Corpse Lily", Rafflesia arnoldii, with a blossom "up to 3 feet (0.9 m) in diameter and weighing up to 25 pounds (11 kg)". Even more amazing, this species is a parasite living completely inside a vine, Tetrastigma, which is a relative of the grape. (Wayne Armstrong's The Stinking Corpse Lily--World's Largest Flower)

The World's Smallest Individual Plant Flower: Wolffia angusta and W. globosa, with common names of watermeal "because they look and feel like small, mealy particles in the water". Their flower is as basic as a flower can be: no petals, no sepals, just a single pistil and a single stamen. The entire plant is so small that "a bouquet of one dozen plants in full bloom will easily fit on the head of a pin". (Wayne Armstrong's World's Smallest Flowering Plant)

Most massive pinecone: 4-6 pounds (2-3 kg), of Coulter pine, Pinus coulteri (Stuart and Sawyer 2001, Trees and Shrubs of California, p.74). Dried cones weigh much less, ~1.5 pounds. Falling from 100 feet up, a Coulter pinecone (or anything else in free fall not limited by air resistance) could reach a speed of 55 mph. This is less than the pinecone's possible terminal velocity of ~80-100 mph that could only be reached by a fall from a greater distance. You would have less than 2.5 seconds to get out of the way.

If a 5 pound pinecone made a direct hit on your head after falling 100 feet, it would be roughly equivalent (in terms of momentum transfer, which is probably the main danger to your brain) to colliding directly with another person's head when you both ran at full speed toward each other. It probably will at least knock you out, and might even be the widow-maker it is sometimes called. However, being hit by a pinecone falling from a tree is a very improbable event unless you are fond of hiking when the wind speed is 100 mph or so.

Most lethally toxic native plants in California: Cicuta, Water hemlock, consisting of Cicuta douglasii, SCo; and C. maculata, CA-FP. (JM, p. 142)

Considered most violently toxic plant in North America. The amount of root that must be eaten to cause death is very small. Botanically related to the infamous Poison Hemlock but toxicologically different. (from Earl J.S. Rook's Natural History of the Northwoods

Species With Color Variants

Percentage of plant taxa that predominantly reproduce asexually or by self-pollination:: 20-25%. (Barrett and Eckert 1990, in Biological Approaches and Evolutionary Trends in Plants, S. Kawano ed., pp 229-254, quoted in Plant Systematics: a Phylogenetic Approach, Judd et al, 2002, p. 143.)

Distance Traveled By Fertile Pollen: 13 miles, for grass pollen (Lidia Watrud et al, Proceedings of the National Academy of Sciences, for creeping bentgrass pollen, Agrostis stolonifera from experimental crop fields in central Oregon, in the print issue sometime around 9/21/04.)

Highest photosynthetic rate measured: for Camissonia claviformis = Chylismia claviformis, a desert annual. In general, photosynthetic rates are high for winter desert annuals since they need to complete their growing cycle quickly, before temperatures get too hot in spring and they run out of water. They do this by optimizing heat in the cool winter, by growth habits (ground-hugging rosettes and solar tracking) and high photosynthetic rates. (Schoenherr 1992, p. 431).

Root properties: Roots of plants are able simultaneously to drive themselves into dirt under positive pressure, while taking in water under negative pressure (Transport of Water and Minerals in Plants)

Tension of water column in vascular bundles in plants: Tensions as great as 3000 lb/in2 are needed to break the column, about the value needed to break steel wires of the same diameter. The tension changes with the transpiration rate, leading to a measurable change in the diameter of a tree trunk over the day. (Transport of Water and Minerals in Plants)

Smallest and largest chromosome number among angiosperms: 2n = 4, in Machaeranthera gracilis, Asteraceae, native to Southern California; 2n ~ 250 in Kalanchoe, Crassulaceae, not present in the California flora. (Plant Systematics: a Phylogenetic Approach, Judd et al, 2002, p. 90.)

Largest chromosome number among ferns and their allies: 2n = 1440, in Ophioglossum reticulatum, Ophioglossaceae. Members of the Polypodiaceae family also have high chromosome numbers. (Plant Systematics: a Phylogenetic Approach, Judd et al, 2002, p. 90.)

Lifetime of individual plants of Nassella pulchra and N. cernua native grasses: at least 100-200 years, and probably 1,000 years! (Hamilton et al 2002, Madrono 49:274-284; J. G. Hamilton 1997, Ph.D Dissertation, UCSB)

Survival time for a teddy-bear cholla, Opuntia bigelovii, without roots: three years. It was still alive after that time after being "completely severed from its roots and suspended on a post in the desert (Gibson and Nobel 1986)", quoted from Plants and Vegetation, Keddy 2007, pp. 148-149.

Other Facts

Largest plant family in California: Asteraceae. (JM, p. 174)

First native California plant to receive a binomial name: Abronia umbellata Lam., Tabl. Encycl. 1: 469 (t. 105). 1791, collected by a French expedition in 1786. (A Species of Eternity, Kastner 1977, p. 294.)

Sequential Germination Of Seeds From a Single Bur: cocklebur, Xanthium fruit, two per bur, which germinate in successive years. (JM, p. 359)

What Is The White Appendage On Seeds Of Miner's Lettuce, Claytonia?: it is an elaiosome (or elaeasome), a "lightly colored appendage filled with oily droplets rich in fat and perhaps sugars," which ants eat after carrying the seed to their nest, and then discard the seed on their "trash pile". This is thought to help in seed dispersal, or in providing the seed with extra nutrients, or by protecting the seeds from fungal decay, predation, and desiccation, or all of the above. No one knows for sure, but it is clearly advantageous: "elaiosomes, and the dispersal of seeds by ants, have evolved at least 86 and perhaps several hundred times around the globe". ("Jaws Of Life: Thousands Of Plants Species Place Their Fates In The Mandibles Of Ants", by Robert R. Dunn, Natural History (Magazine), September 2005, pp. 30-35; see also Some Relationships Between Ants and Plants In Western New York.)

Seed dispersal by ants is "rare in California"; bush poppy, Dendromecon rigida, is another one of those species (Rundel and Gustafson 2005, Introduction to the Plant Life of Southern California, pp. 132-133).

Many Juncus seeds also have white appendages (JM, p. 1157) and are very small, perfect for ants to carry.

Insect Effects:

The cruelest plant to insects?: cruel plant, Araujia sericifera. We found two somewhat different reports of the cruelty of this plant:

  1. from
    The flowers have a very strong scent that can be offensive if approached too closely. This scent attracts night-flying moths that are seeking nectar, but the flowers are designed in such a way as to trap the moths by their tongues until morning when those who have survived the ordeal can escape.

  2. from Landcare Research
    Moth plant is also known as 'cruel plant', bringing both life and death to the monarch. Though it provides nutrients to caterpillars, the flowers trap the mouthparts of feeding butterflies, inflicting a slow death from exhaustion and dehydration.

Murder by Milkweed: Plants in the milkweed family, Asclepiadaceae, have pollen in a pair of massive sacs. The claim has been made that every so often the pollinator bee gets trapped while trying to remove the anther sacs, and dies on the flower. (Fascination of Flowers)

Ill-named Plants:

Species accounting for most of the Agrostis identifications requested at Rancho Santa Ana Botanic Garden: Agrostis diegoensis = A. pallens. (Munz 1974, p. 941)

Species accounting for most of the Gnaphalium identifications requested at Rancho Santa Ana Botanic Garden: Gnaphalium stramineum = G. chilense. (Munz 1974, pp. 170-171)

Longest plant names in our database (not including hybrids):

# CharactersName
All Scientific Names
50Acamptopappus sphaerocephalus var. sphaerocephalus
49Eucrypta chrysanthemifolia var. chrysanthemifolia
Species Scientific Names
30Ornithostaphylos oppositifolia
29Mesembryanthemum crystallinum
29Acamptopappus sphaerocephalus
All Common Names
40backward-splitting Holboell's rock-cress
37weeping-fruited Holboell's rock-cress
37San Clemente Island bird's-foot lotus
37Santa Cruz Island bird's-foot trefoil
37San Clemente Island Indian paintbrush

For comparison, the longest species name in The Plant List, containing 1.25 million species names, is Ornithogalum adseptentrionesvergentulum, with 39 characters.

Shortest plant names in our database:

# CharactersName
8Zea mays
9Poa annua
10Ammi majus
10Carex alma
10Carex feta
10Gilia cana
10Morus alba
10Poa keckii
10Rhus ovata
10Salix alba

For comparison, the shortest species name in The Plant List, containing 1.25 million species names, "includes" Poa fax, with 7 characters. Presumably, there are others just as short since the source used the word includes rather than is.

Go to Native and Introduced Plants of Southern California

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Last update: 2 August 2015