No. 10- January, 2002

Diary of the Benicia Stipa Prairie 1992-2002 with special attention to its recovery after two fires.

Edited and published by Craig Dremann of The Reveg Edge (sm).
P.O. Box 361 Redwood City, Cal. 94064. Phone (650) 325-7333 or e-mail
The URL of this issue is:

If you would like to read the previous and more recent issues about native grasses :
Index at

The New Benicia bridge being built around the prairie, March, 2003
(prairie in foreground).


I have had an opportunity since 1992 to study a relict Stipa (Nassella pulchra) prairie a few miles east of Benicia, within the Caltrans right-of-way in Solano County. The prairie survives along Interstate 680, just 0.2 miles north of the Benicia bridge, and is an intact one acre prairie of Stipa (Nassella pulchra). The prairie has been more or less protected from grazing since the Civil War, when in the 1860's, the land was made part of the U.S. Benicia Arsenal, and has been completely protected from grazing since 1964, when the Interstate was built, leaving this little island of historic California isolated in time.

I discovered the Benicia prairie as I drove by one day in October, 1991. A roadside fire, someone throwing a cigarette into the grassland exposed the Stipa plants, which were resprouting after the burn. With an encroachment permit from Caltrans, I set up a transect through the middle of the prairie, and began monitoring the plant cover, species by species as the plants recovered from the burn. A preliminary report about the Benicia prairie was published in Grasslands in 1994 (Dremann, 1994). During the monitoring period, a second burn occurred in September, 1995 when a Pacific Gas and Electric line went down and started the "Buchanan" fire. Botanical names for plants observed are in Table 1.

Table 1- Plants observed in the first year of Benicia prairie's recovery after fire, 1992.
(Botanical names based on the Jepson Manual) California native plants in bold.

Ambrosia = Ambrosia psilostachya
'Blando' brome = Bromus hordeaceus (syn. B. mollis)
Buckwheat = Eriogonum nudum
Clover = Trifolium sp.
European thistle = Carduus pynocephalus
Fennel = Foeniculum vulgare
Filaree = Erodium sp.
Milk thistle= Silybum marianum
Mustard = Brassica rapa (syn. B. campestris)
Radish = Raphanus sp.
Ripgut = Bromus diandrus (syn. B. rigidus)
Sanicula = Sanicula bipinnatifida. Purple Sanicle or Shoe Buttons
Soap plant = Chlorogalum pomeridianum
Stipa = Nassella pulchra. Purple needlegrass.

Vetch = Vicia sativa
Wild lettuce = Lactuca serriola (syn. Lactuca scariola)
Wild oats = Avena fatua
'Zorro' fescue= Vulpia myuros

Table 2 - Terms used in the article for groups of European exotic plants

Annual grasses = 'Blando' brome, Ripgut, Wild oats and 'Zorro' fescue.
European grasses = Annual grasses
Small annuals = 'Blando brome, Filaree and 'Zorro' fescue.

History of the area.
The history of the prairie was provided by the Benicia Camel Barn Museum, 2060 Camel Rd., Benicia, Ca. 94510. The Benicia prairie was originally part of the Vallejo Rancho land grant, which was deeded to Semple & Larkin in 1847. The prairie became part of the U.S. Army post in April 30, 1849, and the Arsenal when it was authorized in 1851.
The prairie remained part of the Arsenal until 1964 when Exxon purchased most of the former arsenal and built a petro-tank farm. Exxon now uses some of the old military buildings. Another building was turned into the Benicia Camel Barn Museum.

Paul, a volunteer at the Museum who moved to Benicia in the 1940's, remembered that sheep ranchers used to rent land at the Arsenal for pasture, but the sheep have not grazed since 1964. The prairie was further protected for the last 28 years from development when Caltrans built Interstate 680 in 1964, land-locking the strip of land between the Interstate and the railroad tracks.

A new Benicia bridge has been proposed, and future construction of the bridge may impact the prairie.

Observations that were made in 1992 as the prairie recovered from the first fire:

FEBRUARY 9, 1992:
I put orange flags around the burned Stipa area, an area covering about one acre, and set up blue flags for a 100 foot long transect running due south (magnetic) from the USGS benchmark. The prairie burned October 1991 and regrowth is slow due to the lack of rain and unusually cold nights.

Old Stipa plants are spaced evenly, about one foot apart. Soap plants grow in groups, and within their groups also about one foot apart. The burn knocked back the Stipa plants from their original growth.

Seedlings coming up: Filaree enmasse, each seedling 1.5-2 inches across, spaced 3/4 inch apart. Many Stipa seedlings and scattered European grasses, mainly coming up where seeds were protected from fire by deep cracks in the earth or on the insides of gopher holes. In the soil cracks, the European grasses with wide blades are coming up at 2-3 per square inch (144-432 seedlings per square foot), and consist mainly of Wild Oats. Seedlings can be identified by carefully digging up the seedlings and looking for the remains of the seed attached to the roots of the 2 inches tall and 3 inches across seedlings.

Old Fennel plants regrowing but no seedlings present. Old plants are spaced about 10 feet on average, probably coming up in old gopher mounds.

'Blando' brome seedlings are only 1 inch long, thin, light green color, as nights are too cold to obtain soil nutrients. Filaree seems to be inhibiting grass seedlings somewhat. On the other hand, Soap plant seems to be inhibiting the Filaree.

The gopher mounds eliminate all vegetation, except European grasses and some Milk thistle starting at their bases. Without Filaree, the edges of the gopher mounds are the areas of best and densest 'Blando' brome seedling growth and occurrence with 25 seedlings per square inch (3,600 per square foot).

Gopher mounds are also the best Stipa seedling areas, where the seedlings are 4 inches tall and occur at about two per square inch (288 per square foot), and grow best on the downhill slope of the gopher mounds where the bases of the plants have been buried by 2.5 inches of loose soil and have formed a bulb-like structure at the base. These appear to be two year old seedlings coming back up.

The old Stipa plant's damage from the fire is in direct proportion to their age, which is in turn related to their diameter. Much of the Stipa survival depends on whether the plants are in open ground or if they are somewhat protected by the Fennel bushes which act as a moderate fire break.

Stipa clumps, especially when old can be likened to trees. A "pith" forms when the clumps are over 6 inches in diameter which is like the heart wood of a tree. The Stipa's "cambium" is the outer layer of growing and dividing stalks, usually forming a complete ring. The outer ring also keeps the "heart wood" of the bunch intact and protects the center from invasion and being broken apart. One could view the bunchgrass as (not to make a pun) a truncated tree, almost a two-dimensional representation of a tree.

Since the bunch grasses go completely dormant through the summer, the key to survival is the roots: protect the roots and the nutrient and water storage organs.

In one area, Buckwheat is coming up as seedlings, at the rate of one seedling per square inch (144 per square foot), and may have been the original bare-ground fire-colonizer before the exotic Filaree took its place in the natural Stipa prairie.

FEBRUARY 29, 1992
Nearly every Stipa leaf has been eaten to within 1-3 inches of its base, with no consumption of 'Blando' brome, Filaree, or Wild oats seedlings, or Fennel leaves. Some Soap plant leaves have been eaten by the gophers to the ground level.

Table 3 - The size of the seedlings resprouting after the first fire (2/29/1992), natives in bold :

Ambrosia 6 inches tall
'Blando' brome 1 inches tall
Buckwheat 3 inches across
Fennel (sprouting from roots) 8-12 inches tall, no seedlings.
Filaree: 3-5 inches across, some starting to flower.
Milk thistle 8 inches across
Soap plants 12 inches tall when unmolested by gophers
Wild oats: 8-12 inches across

Also seen for the first time in the burned prairie are various European exotics like Vetch and Clovers are appearing. Radish and Wild lettuce also appear, but both are rare. Sanicula bipinnatifida, an unusual-looking native umbell, known as Shoe buttons, is present but is also rare.

Filaree seedlings are starting to colonize burned centers of Stipa clumps. Soap plant, when it grows in colonies, with individual plants spaced about 8 inches apart in each direction, inhibit 'Blando' brome, Filaree, and Wild oat seedlings.

MARCH 28, 1992
There is a striking difference in species composition and height between the burned Stipa area and the burned European grass area:

1.) Stipa area's vegetation is very low, depauperate, as if the bunch grasses did not contain much nutrients in their leaves before they burned, so are not able to provide for dramatic regrowth of seedlings in the Stipa area.

2.) Prior to the burn, the pure European grass annuals seemed to contain high quantities of nutrients, which they more efficiently mine from the soil and store in their leaves---providing after the burn dramatic regrowth of seedlings.

3.) At this point in observations in the Stipa area, the old plants are dominant over Filaree; while Filaree seems to be dominant over European grass seedlings, and perhaps also the Stipa seedlings in the Stipa area.

Table 4 - European weed seedlings coming up in the burned Stipa prairie 3/28/1992
133 Filaree seedlings, 3-8 inches tall flowering and setting seed.
50 'Zorro' Fescue seedlings, depauperate, 2-7 inches tall.
8 Ripgut, depauperate, 10-12 inches tall, setting seed.
3 Wild oats, 12 inches tall, depauperate, setting seed.
2 Wild lettuce, depauperate, 7 inches tall.

APRIL 18, 1992
Stipa and Wild Oats flowering today. Filaree and Small Annual European grasses---'Blando' brome and 'Zorro' fescue--- are drying up.

JUNE 20, 1992
Stipa is about 50% green and the leaves are rolled up for the summer. Stipa and Wild oat seeds are shedding. Fennel and Buckwheat is just flowering. Soap plant's seeds are turning green.

NOVEMBER 1, 1992
We just received 1.25 inches of rainfall so far this autumn on the San Francisco peninsula, but that translates to about 0.75 inch at the Benicia prairie. The soil here is barely moistened, but this small amount of moisture, in only three days, has allowed the Filaree seeds to germinate at the rate of 5-10 seedlings per square inch (770-1,440 per square foot).
None of the Stipa has greened up nor are there other European grass seedlings evident in the burned prairie area.

Table 5 - Transects of four areas (percentage cover averaged) Nov. 1992, native in bold:  
 Fen  Buck-
 Ambr  Must
Unburned Stipa  79.0 10.0 7.33 3.67 0 0 0 0 0 0
Burned Stipa  12.48 7.52 32.19 3.30 42.61 0.47 1.37 .077 0.053 0
Unburned Wild oats  0 87.5 9.5 0 0 0 0 0 0 3
Burned Wild oats  0 52.5 9.5 25.5 12.5 0 0 0 0 0

KEY: "Live Filaree" is bare soil with live filaree seedlings coming up.
"Eur. This." = European thistle. "Dead sm. an." = Dead small annuals and are the
'Blando' brome, 'Zorro' fescue and Filaree plants that grew in spring 1992 and are
now dead. "Fen" = Fennel plants. "Ambr" = Ambrosia. "Must" = Mustard

The percentage cover was measured using a rectangular quadrant 32 inches x 40 inches that was subdivided into 20 equal sized 8 inches x 8 inches squares. For each of the four areas listed above, at least two quads were averaged for the above figures, with the total number of quads as follows: Unburned Stipa n=3, Burned Stipa n=27, Unburned wild oats n=2, Burned wild oats n=2.

NOVEMBER 12, 1992
Nearly all the Filaree seedlings that had germinated from the earlier rain are now dead due to a dry spell after the rain. A few European grass seedlings, all Wild oats survived at the bases of dead wild oat plants, along with a very few Filaree seedlings, and Wild oat seedlings are germinating out of soil cracks. Stipa old plants are greening up.

No Wild oats are growing within a radius of one foot uphill and 1-3 feet downhill of old Fennel clumps, and European thistle, even at low numbers, inhibit all European grasses, at about 15% canopy cover.

DECEMBER 26, 1992
8 A.M.: Foggy and below freezing. Rains in early December have germinated another batch of Filaree and annual grass seedlings to replace those that had grown after the October rains and then died from drought. Annual grass leaf tips are frost-damaged---their top inch varying from red-violet to orange-yellow in exposed areas.

A hawk is seen gliding over the prairie. Cold and foggy day, with visibility about two miles and the wind is 10-15 mph, going from the Central Valley out towards the Golden Gate.

Filaree seedlings are about one inch across. Stipa old plants are 4-5 inches tall of regrown leaves. Scattered Wild oat seedlings, 3 inches tall and Soap plant roots are regrowing. Most of the annual grass thatch has been broken down by the rain; so only stalks over a foot tall that remain standing are the Stipa old plants and Fennel seed stalks.
Some fine-bladed grass seedlings are also coming up, and I will look at them in June 1993 to see if any are Stipa. Currently there is mostly regrowth of the old Stipa clumps, and very little growth of annuals because of the cold---so I don't expect much growth until about February 20th.

PART TWO: Observations and Measurements 1993-1996

Botanical names for plants observed are listed in Table 1 and 2.

Table 6 - Plants observed during Benicia prairie's recovery from 1995 fire, 1993-1996
(Botanical names based on the Jepson Manual) California native plants in bold.

Ambrosia = Ambrosia psilostachya
Annual grasses = 'Blando' brome, Ripgut, Wild oats and 'Zorro' fescue.
'Blando' brome = Bromus hordeaceus (syn. B. mollis)
Blue-eyed grass = Sisyrinchium bellum
Brodiaea = Triteleia laxa (syn. Brodiaea laxa)
Buckwheat = Eriogonum nudum

Clover = Trifolium sp.
European grasses = Annual grasses
European thistle = Carduus pynocephalus
Fennel = Foeniculum vulgare
Filaree = Erodium sp.
Fireweed = Epilobium angustifolium ssp. circumvagum
Golden Aster = Heterotheca grandiflora

Mustard = Brassica rapa (syn. B. campestris)
Red brome = Bromus madritensis ssp. rubens (syn. Bromus rubens)
Ripgut = Bromus diandrus (syn. B. rigidus)
Sanicula = Sanicula bipinnatifida. Purple Sanicle or Shoe Buttons
Schrophulariaceae = Bellardia trixago
Sitanion = Elymus elymoides
Small annuals = 'Blando' brome, Filaree and 'Zorro' fescue
Soap plant = Chlorogalum pomeridianum
Sow thistle = Sonchus oleraceus
Stipa = Nassella pulchra. Purple needlegrass.
Vetch = Vicia sativa
Wild lettuce = Lactuca serriola (syn. Lactuca scariola)
Wild oats = Avena fatua
'Zorro' fescue = Vulpia myuros

Table 7- Plants not observed during Benicia prairie's recovery from 1995 fire,
1993-1996, but were present in 1992. (Botanical names based on the Jepson Manual)

Milk thistle = Silybum marianum
Radish = Raphanus sp.

JANUARY 24, 1993
Filaree and European annual grasses --'Blando' brome , Ripgut , Wild Oats , and 'Zorro' fescue --growing well after rains. Filaree about 1.25 inches across, Wild oats about 4 inches tall. Stipa old plants have green leaves 6 inches tall.

JUNE 5, 1993
Soil is wet from recent rains. General view of burned portion of Stipa prairie is that numerous Fennel seedlings are coming up, as well as Mustard invading from the East in a wave. This year, there is a shocking increase in fennel and mustard seedling densities.

There appears to be much more Wild oats. The 'Zorro' fescue and 'Blando' brome is increasing in density in areas which were laid bare by the fire, and they were the first to colonize those bare areas.

Soap plant has been markedly inhibited by the annual grasses, only thriving now and flowering wherever the Stipa is thick and sheltering it. This year, there is a shocking decrease in the Soap plants.

European legumes are starting to appear: Clover and Vetch . Some Red brome can be found in the unburned area, and is invading somewhat into the burn area. There is a disturbing amount of Red brome coming in. Rarely, Fireweed shows up.

Filaree, which was common everywhere the first year is now giving way to the annual European and native perennial grasses, but still possibly inhibiting Stipa seedling germination.

Any bare soil present at this point is fresh gopher mounds, otherwise all the other bare areas that the burn created are now at least covered with Filaree. I'll be measuring all my transect quads., not as percentage basal coverage, but as canopy cover at one foot off the ground. I've chosen this method because for many of the plants, the Stipa and Fennel in particular, nothing else grows under their canopies.

The Buckwheat is flowering for the first time since the burn. It seems to be able to keep the weed grasses out if the colony is thick and large enough---it needs to be at least five feet across. The Buckwheat patch is spreading rapidly downhill from underground roots and is now 6 feet from the transect headed in an east/northeast direction at 5-6 feet per year.

At the edge of the burn some Sitanion is present---only a very few plants.
The Stipa seed is ripe and about 1/3 of the seed has shed, probably the end of May would have been the best seed collection time.

There is a new composite, only two plants, of Golden Aster, which will flower in a month or two.

A black butterfly is seen in the prairie, colored like a Mourning Cloak and shaped like a Swallowtail but without the tails, an Indra Swallowtail, whose larvae feed on fennel.

There is an unusual European plant in the Scorphulariaceae, only one plant six inches tall, with only two flowers, leaves all clustered on top, arranged in a north/south direction, Bellardia trixago.

There's at least two subspecies of Vetch, both Vicia sativa:
The first Vetch has black pods 1.2 inches long that have already shed their seeds: Vicia sativa ssp. nigra, and the second Vetch has light tan 2 inches long translucent pods with speckled seeds, Vicia sativa ssp. sativa.

Stipa seedling recruitment: there is no evidence of any Stipa seedling recruitment this year even though there have been two seed crops since the burn: the pre-1991 burn seed bank and the 1992 seed crop. There is a new 1993 seed crop maturing right now, and these are the following estimates of seed production for 1993:

I took one square foot of burned Stipa, cut the seedheads and counted 44 seedheads, each producing 15-50 seeds per head with an average of 45 seeds = 2,480 seeds per square foot being produced.

Other grasses:
Wild oats, 32 heads with an average of 15 seeds per head = 480 seeds per square foot. Ripgut, one seedhead per square foot and 22 seeds per seedhead = 22 seeds per sq. ft. Small European annual grass seed production not counted.
At this point gopher mounds may be the only area where Stipa seedlings have a chance to survive, as the Annual weed grasses and Filaree seedlings cover every square inch of potential "nursery" area.

JANUARY 18, 1994
The path that I have been walking down through the prairie to measure the transect is clearly delineated. Due to warm weather and lack of rain, the ground is crumbly-dry but moistened at the surface by morning fog that forms in the Central Valley and wafts out through the straits, evaporating by the afternoon.

The little flattened area where I sat last year is allowing numerous seedlings of that unusual umbell, the Sanicula, to come up, though it is having a difficult time with the innumerable Filaree seedlings that fill every bare spot.

The old Stipa plants are regrowing nicely, with green leaves that are a foot long. The Ripgut and Wild oats are quite long also, about 8 inches. The old and young Fennel plants are still not growing back yet; it has been too cold at night (it still frosts each night in the valley floors). A few scattered plants of Vetch are coming up and growing over the top of the grasses.

Quite a few dead Mustard and Wild lettuce stalks can be seen from last year. There was an average of one Mustard stalk per square yard, and one Wild lettuce stalk per 100 square feet.

The gophers really like the prairie, and it is the only place they live on the hill, where they eat the Soap plant and Stipa leaves. There's no evidence that the gophers were eating anything in the European annual grass area.

MAY 30, 1994
Saw a flock of about a dozen small hawk-like birds swoop around in the ravine just below the prairie. When these birds dive, they hold their wings stiff like swifts, and they are brown-black on top and have a light underside.

Stipa seed is setting and annuals are all dry. The Stipa made a lot of headway against the Wild oats and European thistle due to the drought in the winter 1993-4, but the drought still favored Fennel and Ripgut, which seems to be on the increase.

The best stand of Wild oats is right along the path my feet have made through the prairie to measure my transect. It shows how delicate a native Stipa prairie is---just going in and measuring it can change its species composition.

The Buckwheat patch has some sort of fungus on its leaves, looking stressed. Some Sitanion is appearing in the unburned Stipa area. Small annual European grasses and Filaree are fading from the burned Stipa area. Red brome is fading from the south edge, where it had made an inroad into the burned prairie last year.

Surprisingly, the Soap plant is all gone--perhaps the regrowth after the burn allowed the gophers to find them all---I found one dug-up patch in the prairie.

There is no Stipa seedling recruitment this year, three years after the burn. I checked the seed samples I harvested the last two years and they appear to have Blind seed disease.

JUNE 4, 1995
The 170% of normal annual rainfall has made everything grow well and the Stipa seed has already shed. However, the Blind seed disease is still ± 100% present, as evidenced by the black seeds that are not filled. There are still no Stipa seedlings present, and the old original Stipas that survived the fire are still gaining ground over the weeds.

Filaree and 'Zorro' fescue are almost completely gone, but 'Blando' brome grew tall this year and Ripgut is a real problem. The Buckwheat patch has greatly diminished, and of the Soap plant only one seedhead appeared in the transect.

Many of the weeds are gone or nearly gone: European thistle, Mustard and Red brome. Bare soil is gone except for one gopher mound. There's very little gopher activity compared to past years. Fennel seems up and down. There is no evidence of clovers or yellow Star thistle this year.

Some Brodiaea plants are blooming up in the gravel of the turn-out along the Interstate, which I've never seen. Old Stipa plants that were above the edge of the burn seem to be growing and becoming more evident.

The Stipa prairie burned a second time this month, according to the local fire department: the 'Buchanan fire' was started when a Pacific Gas and Electric wire hit the ground.

JUNE 7, 1996
I checked the seed crop of Stipa produced after the September 1995 fire, and found it fairly free of Blind seed disease for the first time.

AUGUST 11, 1996
The above-average rainfall has caused Wild oats to thrive in the newly burned Stipa prairie, the Fennel was knocked back.

The Ambrosia has spread about five times the area it covered in past years, growing in areas where I have never seen it before. The plant spreads by horizontal roots about two inches below the soil's surface. This plant appears very allelopathic against all European grasses, except 'Blando' brome and Red brome, which likes to grow underneath it. Red brome kills out Wild oats. European thistle and Red brome seem to like to grow together.

The whole prairie burned in September 1995, even places that didn't burn in the 1991 fire. All my transect stakes were burned and pulled up, so I had to re-establish the transect by compass, measuring exactly 90 feet due magnetic north from the USGS benchmark to the start of the transect and the Stipa prairie; then replacing the flags every three feet, to mark off the individual quads, which measure exactly 3 feet by 2.5 feet. The transect then runs another 75 feet due magnetic north through the middle of the prairie.

There are almost no Stipa seedheads present this year, mostly Wild oats. There are a few Soap plant seedheads scattered about 10 feet apart in each direction. The Ambrosia may have acted like a fire-stop to protect some of the Stipa bunches, but many old Stipa bunches died in this fire. In the 1991 fire, they were generally just knocked back only about 50%.
In the European grass area where Stipa has not recently existed European thistle is almost gone, replaced by nearly solid Wild oats in this above-normal precipitation year.

The Buckwheat stand got almost completely killed off. All that remains is a little patch three feet west of the transect where people walked through the prairie earlier in the summer and pushed down the Wild oats. In these pushed-down places, the Stipa plants are taking advantage of the light and regrowing, plus there is some Fireweed in those areas also.

No gophers evident this year, which is a big contrast to the 1991 burn. Found a shedded snake skin, and swallows flying overhead.

 TABLE 8 - BENICIA STIPA PRAIRIE averaged transects,
percentage cover, California native plants in bold:

Two burns occurred: ·<10/91>·...........................................<9/95>·
   Preburn  11/1/92 6/5/93 5/30/94 6/4/95 8/11/96
 Stipa pulchra 79.0 12.48 22.9 29.7 34.6 11.6
 Wild oats 10.00 7.52 3.8 10.8 16.4 22.6
 Mustard 0 0 1.6 0.6 0.4 0.8
 Fennel 0 0.47 5.3 5.8 5.7 1.2
 Ripgut 0 0 1.8 6.4 23.8 4.1
 Eur. thistle 3.67 3.30 4.9 0.7 1.3 4.3
 Sm. annuals 0 42.61 45.0 27.8 4.0 36.8
 Vetch 0 0 1.1 7.1 2.8 7.0
 Sow thistle 0 0 1.1 0.1 0.1 0.05
 Red brome 0 0 2.4 0.1 0.2 0.5
 Wild lettuce 0 0 0.725 0.7 0.6 0.5
 Buckwheat 0 1.37 2.4 2.2 0.8 0
Fireweed 0 0 0.05 0 0 0.05
 Ambrosia 0 0.053 0.7 3.6 8.2 7.0
 Golden aster 0 0 0.02 0 0 0
 Blue-eye grass 0 0 0.004 0 0 0
 Scrophular. 0 0 0.001 0 0.1 0
 Bare soil 7.33 32.19 5.3 4.1 0.9 3.5
 Clover 0 0 0.9 0 0 0
 Soap plant 0 0.007 0 0.3 0.1 0
 Star thistle 0 0 0 0 0 0
 Stipa seedlings? Yes No No No No No

PART THREE: Observations and Measurements 1997-2002 and Summary

Botanical names for plants observed appear at the end of the article as a table.

Table 9 - Plants observed during Benicia prairie's recovery from 1995 fire, 1997-2000.
(Botanical names based on the Jepson Manual) California native plants in bold type.

Ambrosia = Ambrosia psilostachya
Annual grasses = Blando' brome, Ripgut, Wild oats and 'Zorro' fescue.
'Blando' brome = Bromus hordeaceus (syn. B. mollis)
European grasses = Annual grasses
European thistle = Carduus pynocephalus
Fennel = Foeniculum vulgare
Filaree = Erodium sp.
Mustard = Brassica rapa (syn. B. campestris)
Red brome = Bromus madritensis ssp. rubens (syn. B. rubens)
Ripgut = Bromus diandrus (syn. B. rigidus)
Sanicula = Sanicula bipinnatifida. Purple Sanicle or Shoe Buttons
Small annuals = 'Blando' brome, Filaree and 'Zorro' fescue.
Soap plant = Chlorogalum pomeridianum
Starthistle = Centaurea solstitialis
Stipa = Nassella pulchra. Purple needlegrass.
Vetch = Vicia sativa
Wild lettuce = Lactuca serriola (syn. Lactuca scariola)
Wild oats = Avena fatua
'Zorro' fescue = Vulpia myuros

Table 10 - Plants not observed during Benicia prairie's recovery from 1995 fire,
1997-2000, but were present at least one year during the period 1992-1996
(Botanical names based on the Jepson Manual), with native plants in bold.

Blue-eyed grass = Sisyrinchium bellum
Buckwheat = Eriogonum nudum

Clover = Trifolium sp.
Fireweed = Epilobium angustifolium ssp. circumvagum
Golden Aster = Heterotheca grandiflora

Milk thistle = Silybum marianum
Radish = Raphanus sp.
Sanicula = Sanicula bipinnatifida. Purple Sanicle or Shoe Buttons
Schrophulariaceae = Bellardia trixago
Sitanion = Elymus elymoides
Sow thistle = Sonchus oleraceus

JANUARY 18, 1997
Mustard is growing above the European grasses, about 10 inches tall and 8 inches across. The European grasses are less than 10 inches tall and growing through old thatch in the burned areas, where the thatch is 3 inches thick. European grasses are stunted by the cold nights and wind, with brown colored leaf tips. Vetch is growing above the European grasses, about 8 inches tall. Temperatures are very cold, near freezing at 2:00 P.M. with wind.

Filaree in all bare areas, about 3 inches in diameter. Because of above-normal seasonal precipitation, Mustard plants are 8 inch diameter plants. Stipa is in excellent shape, about 8 inches tall and dark green. Fennel seedlings are 5 inches tall. Soap plants are 8-10 inches tall, doing well. Small annual grasses like 'Zorro' fescue are about 3 inches tall.

There is a huge amount of gopher grazing on the Stipa, but none on the European grasses. There's going to be the biggest Ambrosia cover in the new burn area, maybe 25-35% cover overall, which hopefully may help the Stipa understory.

FEBRUARY 21, 1997
Today is a very warm day, 65° F. at 3:30 P.M. Everything growing fine with lots of moisture even after two weeks of dry weather since ± February 7th. Stipas about 16 inches tall, very evident. Lots of Soap plant.

Vetch (Vicia sativa) is 8 inches tall. This vetch has weak tendrils, 6-10 opposite leaves, and single flowers coming out of the axils, with "batwings" also coming from the axils. The flower's banner is white and light purple, and the keel is red-purple. Each leaf has a tiny point at the tip. The Vetch is growing over all the grasses, but are more concentrated around or amongst the Stipa and fairly common in the Wild oats, but rare among the small annual European grasses.

Wild oats or Stipa and Vetch seem to have a synergistic effect---the plants of the Vetch grow larger and stronger among the Stipa than with the small annual European grasses.

Fennel seedlings are small about 8 inches tall, and old plants are vigorously resprouting. Mustards are in rosettes about 8 inches across.

Ripgut and Wild oats are 8 inches tall. Other small annual European grasses are about 6 inches tall, growing very densely, with about 100 'Blando' brome seedlings to the square inch (14,400 to the square foot), but they only fill in the spaces between the Stipa, Mustard, and Wild oats which occupied the ground first.

I saw my first jackrabbit ever in the prairie area. In areas around gopher mounds---and gophers are numerous amongst the Stipa and absent outside of the Stipa prairie---the gophers have cropped the Stipa leaves to about half their length, to about 8 inches tall.

Soap plant, which likes the Wild oats, Stipa and Ambrosia areas, can be found evenly scattered about 10 feet apart with 16 inch long leaves. The Ambrosia leaves are about 8 inches long.

APRIL 9, 1997
We had a flood of rain in early January, which got all the seeds germinating and plants growing, but the lack of any rainfall since early February and warm weather has completely changed the plant community here.

The Stipa seedheads are towering over the depauperate one-foot tall Wild oats and Ripgut. The Stipa is very purple, just finishing flowering and with the dry weather may be having trouble with the dry soil trying to move phosphorus to make seed---the seedheads are very purple, living up to its name "Purple needlegrass".

Soil is so dry that the Soap plants are wilting and will probably not make seed. The Ambrosia is doing well, spreading and appearing in areas never seen before. Ambrosia spreads by horizontal runners that are just an inch or so below the surface. Mustard is doing well, with its best growth ever.

 Table 11 - Benicia prairie, wet winter and dry spring, favors or inhibits the following,
with native plants in italics
 Favors Inhibits No Effect
 Ambrosia Fennel, old plants 'Zorro' fescue
 Fennel seedlings Ripgut  
 Mustard Soap plants  
 Stipa, but may lower seed production Wild oats  
 Vetches, legumes    

In the ravine north of the prairie, there are three huge patches of about 1/3 acre each of Purple vetch in solid stands, which I've never seen before.

'Zorro' fescue already has ripe seed, and the Ripgut and Wild oats will be shortly behind. Mustard plants are huge, about 4 feet tall, as well as the Stipa seedheads. Ambrosia is growing in dense, large colonies, about 2 feet tall, and covering 50 feet by 50 feet at a time.

JUNE 14, 1997
The huge Mustard plots have overgrown and killed most of the annual European grass understory, overgrowing all the annuals due to the lack of spring rain since early February and a hot, dry spring. The Stipa seed is just ripe this week and the weather is clear, cool and breezy. Even with the two previous fires, the population is showing this year's seed is >80% infected with Blind seed disease.

Stipa leaves are still green to 16 inches long, and are not seemingly bothered by the Fennel or Mustard, I speculate that this is because light can get down to them and they can photosynthesize into the summer; whereas the tall European annual grasses have cut off the light to the Stipa by now.

You can see the ground directly under the Mustard plants, and the few grasses underneath them are actually blackened from the chemicals exuding from the Mustard---really black-black---and there's a dead-zone around each Mustard plant about 3 feet across. The Mustard does kill Stipa that is directly underneath it. I am speculating that the Mustard allelochemical is probably secreted at night in dew-drip or in the fog-drip. The chemical is probably absorbed by dead grass stalks, and re-released in winter when rains wash it back into the soil.

The Fennel have also thrived during this dry spring, growing taller than ever with the lack of allelopathy they usually receive from the annual grasses. The Fennel is now 4-8 feet tall when they are usually ± 3 feet tall.
The Buckwheat is blooming.

JULY 23, 2000 - Revisiting the Prairie.
I haven't been out to the prairie since 1997. Wild oats and Ripgut are very rare. 'Blando' brome and Red brome are doing very well in the Ambrosia stands. Stipa seedlings are appearing for the first time ever in the transects, and they may be up to 2-3 years old. Mustard plants form a large dead-zone underneath each plant, about 16 inches in diameter. Half of the old Fennel plants died last year, perhaps due to the ± complete lack of rain during October to December.

March 24, 2002 - Revisiting the Prairie.
Sunny day, just rained last two days, windy, in the 50s-60s, with an amazing change in the vegetation--an even more dramatic change than with the previous two fires! There was almost no rainfall in the month of February, and the weather was in the 70s--basically May/June weather. This unusual weather only allowed the broadleaf weeds to grow, and there's almost no annual grasses.

 Table 12 - Benicia prairie, very dry, hot February, favors or inhibits the following, with native plants in Italics:
 Favors  Inhibits  No Effect
 European Thistle  Stipa, old plants  Red brome
 Soap plant Ambrosia Sow thistle
 Stipa seedlings Fennel Wild lettuce
 Vetch Mustard  
  Small annuals  
Ripgut grass  
 Wild oats  

The lack of rain, which has inhibited the annual grasses, has allowed for an explosion of Soap plant and Blue-eyed grass. Vetch, and European Thistle are abundant everywhere. Soap plant and Stipa seedlings can even be seen in the old non-native areas. Seen for the first time, about 100 feet north of the survey marker is Amsinckia!

Ambrosia is now very suppressed because of the lack of rainfall, and is very depauperate. Lots of ladybugs up to two per transect, and saw some larvae. Saw one lizard, and one mushroom, about one inch tall and the cap buff-colored 1/2" across. No old fennels seen, only a few seedlings. Even during both burns was there a complete die-off of the old fennel plants.

Ripgut grass is as depauperate as it can get and still reproduce--8" tall and only 2-3 seeds and barely any leaves. Just putting all the energy into making those three seeds. The whole community is only 4-8" tall. There is so much European thistle you need something to sit on.

Two new weeds never seen before: Bindweed and Wild geranium. Only one Bindweed plant in one transect, but in places the Wild geranium is thick, and seems to be coming in from the highway roadside. First time seen one annual Lupine plant, but it is probably a waif from the roadside plantings closer to the bridge for the bridge reconstruction.

The Blue-eyed grass seems to be in association with the Ambrosia, the Ambrosia able to keep the annual grasses away. The Blue-eyed grass needs very low surrounding vegetation, less than 4" tall, but European Clovers kill them out.

All the plants in the prairie are growing from shoe-high to ankle-high. There are a very few mustards, but they are depauperate, scattered individuals spaced about 20 feet apart, with a single to maximum of three stalks, with only a few flowers at the end of each stalk.

In the non-Stipa area, a few artichoke thistles, which I don't recall ever seeing before.

Past measurements of the Stipa have not been difficult, because most of the other species did not smother the Stipas plants. However, the European thistle and Wild geranium do, so sometimes you don't see the Stipa because those two can grow in towards the Stipa's center and shade the Stipa.

 TABLE 13 - BENICIA STIPA PRAIRIE averaged transects,
percentage cover, California native plants in bold
Two burns occurred:<10/91>·.................<9/95>·
 No rain
in Feb. 2002
   Preburn  11/1/92 6/5/93 5/30/94 6/4/95 8/11/96  6/14/97  7/23/00  3/24/02
 Stipa pulchra 79.0 12.48 22.9 29.7 34.6 11.6  22.3 15.25  10.2
 Wild oats 10.00 7.52 3.8 10.8 16.4 22.6  8.1 1.25  2.9
 Mustard 0 0 1.6 0.6 0.4 0.8  4.5 9.65  0
 Fennel 0 0.47 5.3 5.8 5.7 1.2  4.0 3.0  0.8
 Ripgut 0 0 1.8 6.4 23.8 4.1  6.2 1.3  1.5
 Eur. thistle 3.67 3.30 4.9 0.7 1.3 4.3  0.4 3.1  31.8
 Sm. annuals 0 42.61 45.0 27.8 4.0 36.8  31.9 30.45  33.2
 Vetch 0 0 1.1 7.1 2.8 7.0  4.5 3.8  8.3
 Sow Thistle 0 0 1.1 0.1 0.1 0.05 0 0.1  1.7
 Red brome 0 0 2.4 0.1 0.2 0.5  0  5.7  2.0
 Wild lettuce 0 0 0.725 0.7 0.6 0.5  0  0.05  0.8
 Buckwheat 0 1.37 2.4 2.2 0.8 0  0  0  0
Fireweed 0 0 0.05 0 0 0.05  0  0  0
 Ambrosia 0 0.053 0.7 3.6 8.2 7.0  15.7 19.8  2.0
 Golden aster 0 0 0.02 0 0 0  0  0  0
 Blue eye grass 0 0 0.004 0 0 0  0  0  0
 Scrophular. 0 0 0.001 0 0.1 0  0 0  0.02
 Bare soil 7.33 32.19 5.3 4.1 0.9 3.5  0.7 5.6  2.1
 Clover 0 0 0.9 0 0 0  0 0  1.5
 Soap plant 0 0.007 0 0.3 0.1 0  1.7 0.9  0.6
 Star thistle 0 0 0 0 0 0  0 0.05  0
 Bindweed 0 0 0 0 0 0 0 0  0.1
 Wild Geranium 0 0 0 0 0 0 0  0  0.48
 Stipa seedlings?  Yes  No No No No No Yes Yes Yes


Below is a condensation of the major observations that I have made while monitoring the regrowth and effects of the two fires on this Stipa prairie near Benicia.

BLIND SEED DISEASE on Stipa, and RUST on Buckwheat.
The Stipa has been infected by Blind seed disease, a pathogenic fungus, Phialea temulenta, which stops Stipa's seed reproduction on an annual basis, and when the disease is present, there is no seedling recruitment. The disease was probably spread into the prairie from a European grass host, from one of the introduced grasses found in or around the prairie. Houston (1973) lists "Zorro" fescue as one of the known carrier hosts of the disease.

The Buckwheat stand was infected by rust, also possibly from a European host plant, and was completely killed out. Knowledge of these diseases and how to treat them will be of the greatest importance for the restoration practitioner and native grass ecosystem manager, so that disease doesn't effect the ultimate long-term survival of your grasslands.

LETTING THE LIGHT IN: The portion of the original Stipa prairie that never burned is still in good shape. The Stipa plants everywhere are doing best each year where they are not shaded out during the spring by taller exotics. If the shading of the Stipa occurs during the time they are trying to photosynthesize and store carbohydrates for surviving through the summer, the plants appear to be weakened by the end of summer.

CHAOS: Typically, the Stipa plants are ancient anchors in the grassland or prairie ecosystem, maintaining themselves in one place as individual plants for 20-100 years or more.

Observing this Stipa prairie and its regrowth after two fires, I've observed a concept that I will call "Chaos". The Stipa prairie's has a chance to succeed over time if it starts out with 80% cover or better. When you have less than 80% cover, the grassland has difficulty withstanding the Chaos that is introduced into the system by the exotics. Each exotic annual tries to take advantage of space each year within the prairie ecosystem so they can grow and reproduce seed again.

The Chaos of the exotic annuals comes in after the fire to occupy every square inch around the Stipa; and because there are several species of annuals, this mob of annuals are all competing for the nutrients and space, and want to reproduce seed. When the besieged Stipa is also infected with Blind seed disease, then the Stipa is unable to take advantage of favorable conditions for reproduction and the native plants have a difficult time of holding together as a solid prairie ecosystem.

FIRE AS A MANAGEMENT TOOL FOR STIPA PRAIRIES: Prior to 1750 , before European exotics became naturalized in California, fire had a zero net effect on the grasslands, that it was neither positive nor negative within a functioning, intact ecosystem. Fire would just favor certain native plant families over another.

For example, a fire through a Stipa prairie in 1750 might decrease Stipa cover and increase the spread of edible lily- family bulbs, or increase the edible clovers which were used for food and natural birth control by the indigenous peoples.
Once exotics became naturalized, fire as a tool for Stipa (Nassella pulchra) grassland management and enhancement tool becomes problematic. As seen in the Benicia prairie, the percentage of Stipa cover the first year after fire was consistently depressed to a staggering low of 12% (±1%) and recovers the second year to only 22% (±1%) cover. The rate of Stipa recovery after fire every year thereafter was only 5-10% per year. Conceivably it could take a decade or more before a stand recovers to a pre-burn 80% cover.

The larger issue of the use of fire alone as a management tool in Stipa (Nassella pulchra) grasslands is that fire now adds a new Chaos factor into the native ecosystem. Burning alone lowers the percentage cover of Stipa, and creates open ground for the weeds to colonize and fight over for at least the next decade. Fire creates an open battleground for the exotics to interject their own Chaos into the native ecosystem.

However, burning could possibly be part of a burning-and-reseeding program for a Stipa prairie. If the burning was done a few weeks after the first autumn rains when the old Stipa has started to green up, thereby protecting them from the effects of the fire; and then immediately seeding the burned areas.

Also, it would be necessary to add the following items immediately after the burn, to give the Stipa a competitive advantage over the exotics:

1.) Sow in large quantities of local Stipa seed (>50 pounds to the acre).
2.) Add any nutrients necessary to correct any deficiencies, especially phosphorus.
3.) Add local Stipa straw mulch to replace what was burned, so there is no net loss of soil carbon or organic matter from the ecosystem.

When you survey the vicinity of Benicia along Interstate 680 for 10 miles from the Benicia bridge north to the junction of Interstate 80, and only find that there is only one acre left of a Stipa prairie, then a relict native grassland stand of any size or diversity appears very important. There is so little remaining of the California grassland biome, that we may erroneously feel that if we just protect some of what is left, that will be adequate for the continued survival of the grassland species.

However, since we have converted 99.99% of the <3,000 ft. elevation California grassland biome into an annual exotic grass area, those exotics on the border can cause continual future chaos in the relict stands of natives. If there is good diversity, then small fragments of native grassland may be able to survive if it can withstand the onslaught of exotics. However, when the percentage cover is too low, even large contiguous stands can face a slow-motion extinction of that stand within 10-50-100 years.

The best possible solution for the future survival of California perennial grasslands future survival, is to try and maintain a "no net loss" policy over the next 50-100 years, protect what is left, and monitor their survival, especially their interactions with the exotics. There will probably need to be legislation introduced, like there was to protect wetland areas, so that we will start paying attention to what relicts remain.

Acknowledgment: I want to thank the Environmental division of Caltrans for signing and renewing the Encroachment permits, which allowed me to monitor and record the annual changes in the Benicia Prairie.

Literature cited:
--Couch, Houston B. 1973. Diseases of Turfgrasses. Second Ed. Robert E. Krieger Pub. Co., Malabar, Fl. Pg 148-152.
--Dremann, Craig C. 1994. Relic Prairie Finder: Benicia Prairie. GRASSLANDS 4 (3) 4-5.
--Hickman, James C. 1993. The Jepson Manual: Higher Plants of California. University of California Press, Berkeley and Los Angeles, Ca. 1,400 pgs.

Design for the transect can be found at

The new Benicia bridge being built around the prairie, March, 2003

Updated December 23, 2022 - The Reveg Edge Ecological Restoration services.