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Oakmead Herbarium: Arrivals, Weeds

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Ongoing research and support activities at JROH include field observation, data recording, specimen collection, voucher preparation, conservation, database management, and collection and curation of digital imagery.  Through these activities, new invasive species such as Dittrichia graveolens, Brachypodium sylvaticum, and Parentucellia viscosa were detected early enough that their populations could be controlled (Jasper Ridge Oakmead Herbarium, JROH)

How should we guide management . . . My philosophy has four components

  1. The first is to manage with the lightest touch possible, respecting the path that nature determines.
  2. Second, we have the opportunity and the responsibility to learn by doing. In our everyday management decisions, we continuously face the question of whether to remove an invasive species, exclude an animal, or mow here rather than there. Docents and staff have managed to keep up with removal of certain invasive plants (e.g., stinkwort, pampas grass, tree-of-heaven), and are making inroads against others (e.g., French broom, yellow star-thistle). We continue to debate an experimental return to cattle grazing as a management tool. 
  3. Third, we can learn from others, building on the rich diversity of approaches and outcomes that we see in nearby preserves and parks. our mission is unique, but wisdom depends on openness to shared knowledge.
  4. Fourth, much of the management of Jasper ridge is grounded in expert judgment. in some ways, our philosophy may be a bit eclectic, based more on a sense of what is possible than on systematic pursuit of defined goals, but it is based on many decades of collective experience by leading ecologists. The criteria and objectives may not always have the sharpest focus, but they always have a rich “feel” for the system. 

Chris Field, Preserve What? JRBP Annual Report 2013-14,  JRBP Faculty Director 

One of those questions, and a current focus of research of the preserve, is how to best go about successfully preserving nature, or what is known as intervention ecology. "When Jasper Ridge was formally designated as a preserve, there was good reason to believe that it was a self-sustaining environment, that natural processes would sustain the natural biodiversity, for example," said Chiariello. "That worked for a while, but it's now clear that with invasive species and other pressures that won't be a sustainable practice for the future."

In 2004, a new strategic plan for Jasper Ridge revised the founding "do-not-interfere" policy and opened a case-by-case discussion on how to strategically tweak an existing ecosystem – either at the preserve or elsewhere – to put it back on a natural path. "We're really interested in restoration now, but to do this effectively we need to first know, for instance, how important it is that you seed an ecosystem with a critical species first so that it can take off on its own," Chiariello said. "We can begin to understand that with the Mimulus system." (

Nona Chiariello, JRBP staff scientist

Like it or not, all our concepts for evaluating ecological change are based on cultural (and therefore changeable) values. Stephen Jay Gould once wrote that the one and only biological defense he could concoct for native species was the protection they “afforded against our overweening arrogance.” We can know how native flora behaves in its existing habitat, but we can never know the long-term consequences of introductions into new habitat. Only a small percentage of novel species will become nuisances, but we are bad at predicting which ones. Although Gould considered the biological argument to be “no mean thing,” he added an ethical defense: by privileging natives, we discourage “the botanical equivalent of McDonalds’ uniform architecture and cuisine” and promote a “maximal amount of local variety.” . . .  No one likes the sound of the Homogocene, the neologism for the current era of human-facilitated species shifting. To flatten the world with sameness seems unethical. It goes against the current of evolution.

—Jared Farmer, Trees in Paradise, p. 213

While the rate of naturalization by exotics at Jasper Ridge may have leveled in recent years, new species capable of moderate to severe impacts continue to arrive. These include over the past three decades Brachypodium distachyonBrachypodium sylvaticumBriza maximaDittrichia graveolens (Aster Family), and Ehrharta erectaLolium multiflorum, long present on the Preserve and recorded in each flora beginning with Springer (1935) invaded the serpentine prairie during the 1960s becoming a dominant plant of that habitat. > = post; < = prior to; CCH = Cosortium of California Herbaria

Documented waifs, agricultural weeds, garden escapes, and eradicated exotics

N = not treated in The Jepson eFlora; SPEC—Specimen, at the Jasper Ridge herbarium (JROH);  DOC—Documented, plant observed and/or photographed by herbarium team but not vouchered

     Abutilon theophrasti (VELVET-LEAF)  camera icon Photo —  SPEC | eFlora — Collected 2006 from resident ranger's yard
N  Acer palmatum (JAPANESE MAPLE)  — SPEC — Young plant collected in 2002; not seen since
N  Agapanthus (LILY-OF-THE-NILE) camera icon Photo — DOC — Red-Hot Poker Meadow. Persistent  
     Amaranthus retroflexus REDROOT PIGWEED — SPEC | eFlora — Ag weed reported in 1974 and 1975
     Avena sativa — SPEC | eFlora — One plant found in dry bed of Searsville Reservoir; 2022
     Borago officinalis (BORAGE) — DOC | eFlora — One plant found in the Corte Madera Cr flood plain in 2003; not seen since
N  Cannabis sativa (HERB) camera icon Photo — SPEC  — Extirpated
N  Cedrus deodara — SPEC | eFlora — Single small tree near Mapache fenceline. Persistent?
     Coreopsis tinctoria (CALLIOPSIS) camera icon Photo — SPEC | eFlora— Collected in 1997 at Low Flow Crossing; not reported since
N  Crataegus laevigata (SMOOTH HAWTHORN) — SPEC — Single plant removed
     Cyperis difformis — spec | eFlora— Collected in 1980; not reported since
     Dichondra sp. — DOC — Herbarium 7/27/2005 Bear Cr. crossing; not seen since
     Geranium core-core (ALDERNEY CRANE'S-BILL) — SPEC | eFlora
N  Hyacinthoides hispanica (SPANISH BLUEBELL) — SPEC— Near Douglas Iris site. Persistent
     Iberis umbellata (CANDYTUFF) camera icon Photo  — SPEC | eFlora — Persistent
     Impatiens balfourii (POOR MAN'S ORCHIDcamera icon Photo — SPEC | eFlora— SF Creek bed; collected once and not seen since
     Ipomoea purpurea (COMMON MORNING-GLORY) — DOC | eFlora
     Lepidium campestre ( FIELD PEPPERWORT) camera icon Photo — SPEC | eFlora — Collected in 1976 in the Searsville Lake–Corte Madera Cr delta; not seen since
     Leucanthemum vulgare — SPEC | eFlora
     Leucojum aestivum (SNOWFLAKE) —  DOC | eFloraFlickr, Calflora
     Ligustrum vulgare (COMMON PRIVET) camera icon Photo — SPEC — Persistent 
     Linaria bipartita — SPEC | eFlora — Two plants in May, 1982 along Sand Hill Road
     Lobelia erinus (GARDEN LOBELIA) camera icon Photo — SPEC | eFlora
     Lycopersicon esculentum (TOMATO)— SPEC | eFlora
     Medicago sativa (ALFALFA) — DOC —  Springer 1935 “infrequent”; Herbarium report 2000, Rd C bridge
     Myrtus communis (COMMON MYRTLE) camera icon Photo — SPEC | eFlora— Hermit'a Cabin Site. Persistent, spreading by rhizomes
     Panicum miliaceum ssp. miliaceum (BROOMCORN MILLET) camera icon Photo — SPEC | eFlora — Collected once 9/2002 in dry bed of Corte Madera Cr; not reported since
Parthenocissus quinquefolia (VIRGINIA CREEPER) — SPEC | Calflora — Scattered plants in Bear and SF creeks; persisting at least from 2011
     Pelargonium grossularioides — DOC | eFlora — 2020
     Phleum pratense (TIMOTHY) — SPEC | eFlora — Collected 7/1/2009 in Bear Creek; not reported since
     Pisum sativum  (COMMON PEA) — SPEC | eFlora — Collected in 1967 along Rd D; not reported since
N  Pinus sylvestris (SCOTCH PINE) camera icon Photo — SPEC — Persistent; a few survivors of Xmas tree farm
     Rhamnus alaternus (ITALIAN BUCKTHORN)— SPEC — One plant persistent since 2016
     Ricinus communis (CASTOR BEAN) — Calflora
N  Rosa banksiae (LADY BANK'S ROSE) camera icon Photo — DOC — Single plant at Hermit Cabin site. Persistent?
N  Rosa laevigata (CHEROKEE CLIMBING ROSE) camera icon Photo  — SPEC — Planted along the Sand Hill Rd. fence between 1975-1980; persistent. Prickles like R. californica
N  Rosmarinus officinalis (ROSEMARY) camera icon Photo — SPEC — Occasional plant found and removed. Persistent?
     Sisymbrium officinale (HEDGE MUSTARD) — SPEC (1935) | eFlora; Dengler 1975; not reported since
     Vicia disperma (EUROPEAN VETCH) camera icon Photo — SPEC | eFlora — Persistent?

Arrival dates of some naturalized grasses

Some non-graminoid arrivals

Weeding Projects

Vegetation Cover Estimate Diagrams

Managing invasion by stinkwort, Dittrichia graveolens, 2005-

Teasel, Trail 10 seasonal wet meadow, 2024-. Growing with Asclepias fascicularis at head of meadow

Managing invasion by Parentucellia viscosa, 2005. Still abundant on SLAC

French broom removal in oak-California fescue woodland between trails 4 and 5 

Broom control requires continuous removal until the seed bank is depleted. California fescue thrives in open oak (blue, black, coast live) woodland on a section of the north-facing slope from the ridgeline downhill to the broadleaf evergreen forest below. Substrate includes Serpentinite, Chert, and small zone of Whiskey Hill Sandstone. There are two French broom infestations in this habitat. The upper infestation is about 50 yards long and 5 yards wide and is on the edge of a small drainage. It begins 100 yards or so downhill from trail 4 at 0568073, 4140254. California fescue is growing among the broom. The lower infestation is of similar extent. 

This site has excellent floristic value providing habitat for a number of native forbs and grasses, and its understory is dominated by California fescue, which can form a high percentage of cover. This is one of the few terrestrial habitats on the Preserve where the herbaceous phytomass is largely native. A student project used this site in 2008 (Tom, M. 2008. Ecological impacts of French broom invasion management. Senior honors thesis. Department of Biology, Stanford University).

Extensive California fescue woodland is also found on north-facing serpentine slopes on Mount Tamalpais, where it grows in association with oaks, douglas fir, and serpentine chaparral. The Tamalpais habitats can be extensive. As at Jasper Ridge, the California fescue can locally form a dense cover. On Tamalpais as the slope aspect changes from northeast to northwest, widely spaced serpentine reedgrass replaces California fescue as the dominant graminoid. On Jasper Ridge as one follows trail 4 south, the fescue is replaced by annual grasses and a suite of natives characteristic of drier habitats (Nassella lepida, Nasella pulchra, Koeleria macrantha, Elymus glaucus, Poa secunda secunda). 

Dec 28, 2006 was the first broom pull. Removed 2,500 plants from the upper infestation, including most of the seed-producing plants. There is a good deal of clean-up required of small plants; most of this work could be done by hand-pulling. We plan to return over the next several weeks or months to complete work on the upper infestation.

  • February 7, 2007. Removed 500+ plants from upper broom population.
  • February 21, 2007. All seed-bearing plants removed from upper population, about 1000 plants. Started removal of lower population. 4 hours. Hartweg's tauschia leafing out in the area.
  • February 23, 2007.  Lower population, 1,000+ plants removed, mostly woody. 4 hours.
  • March 4, 2007. 1,500 plants removed lower population. 4.5 hours.
  • March 8, 2007. 1,500 plants removed lower population. All flowering plants removed from both populations. Also 1 cotoneaster and olive removed from upper, and 1 cotoneaster from lower.
  • March 23, 2007. Removed a few hundred seedlings and larger plants previously overlooked, downslope toward small drainage, some in bloom, hand pulling and weed wrench. California King snake in grass.
  • Nov, 2008. 
  • Nov 2, 2008. Removed a few hundred seedlings, hand pulling
  • Nov 5, 2008. Removed a few hundred seedlings, hand pulling
  • Jan 21, 2008. Removed a few hundred seedlings and some older plants in zone downslope nearest Trail 5, hand pulling
  • 2009-2016. Site clean-up of seedlings, hand pulling
  • Feb 27, 2024. Removed 5,000+ individuals, 20 cumulative volunteer hours, hand pulling or weed wrench, stacked in 6 piles located away from the Cal fescue understory. Photographs from weeding session
  • March 19,2024. Removed many large plants downslope in drainage toward Trail 5

Other French broom removal and clean-up

  • Low-flow crossing 2020-2023
  • Trail 1 west of first redwood grove 2023
  • Douglas iris site at confluence of Bear/SF creeks, 2005 to present; (many mature plants and seedlings). This small area is one of the finest native plant habitats on the Preserve. Douglas iris site vicinity: 100 mature and seedling plants removed in November 2010 and 1/21/2011 on slope leading down to Bear Creek on the uphill side of road-end where the Plectritis spp. and Collinsia heterophylla populations were threatened.
  • Trail b near Rd F (50 young plants removed by hand-pulling in 2005, new invasion). Occasional cleanup including 5 small plants 4/4/2013.
  • Semaphore grass vernal pond, many mature plants removed (originally a ranger project). More recently broom removed in general area (Trail 18) by work crews.
  • Trail 7 just south of Hillside Lab 100 plants in 2011-2023 near Festua elmeri site.
  • Bear and SF creeks: Acacia dealbata mapping (partial), 2021
  • French broom stand north bank of SF Creek (proposal)

Chia site Trail b

Ongoing weeding of tocalote, Italian thistle, and scarlet pimpernel in loose scree resulting in a vigorous recovery of native species: Salvia columbariae, Phacelia rattanii, Cryptantha microstachys, Rafinesquia californica, and Pellaea mucronata.  camera icon Photo 

Field Station area

The herbarium group sponsored weeding sessions Sunday 9/21/2014 and Monday 9/22: 9:00-11:00 AM each day. The site is down slope from the field station toward the lake where grows the Preserve's only population of Goldenaster. The rare wooly-headed Lessingia was also blooming nearby as well as hayfield tarweed, hairy birdbeak, and naked buckwheat. 

Bear Creek (Parthenocissus)

9/20/2017 "We walked Bear Cr from Sand Hill to the confluence with Corte Madera and removed Parthenocissus from 6 locations, including two on the South side of the creek (one was climbing in a willow).  We got all the roots we could from all patches." -- Nona Chiariello

Marsh (Brachyposium sylvaticum)

6/2016 Thousands of plants removed from marsh area in June 2016. First report of a single plant in 2007 inside the Sand Hill Road. Fence near its west end south of the main gate. One plant discovered along Rd G in 2014; removed. This distinctive perennial forest grass has sessile spikelets, long-awned lemmas, and densely hairy nodes. It has naturalized and is locally abundant in Wunderlich Park (San Mateo County) and MPROSD Thornewood Preserve and adjacent private land. (MROSD. 2016. Ten-year Status Report and Recommended Continuation of a Slender False Brome [Brachypodium sylvaticum] Integrated Pest Management Program.)

9/2021 Bill Gomez and JR removed about 500 plants from a second marsh location in the Corte Madera Delta area.


Sources: references relevant to the floristics of Jasper Ridge Biological Preserve.

Brachypodium distachyon was first noted on the Preserve June 4, 1977 by Herb Dengler “west of the lake above the beach (second year of drought).” (Specimen: Dengler s.n. ) This grass was not recorded in John Thomas (1961) Flora of the Santa Cruz Mountains of California.
2 A single plant was found in 2007 inside the Preserve’s Sandhill Rd fence south of the main gate; the plant was removed. A single plant was discovered along Rd G in 2014 and removed. In Fall 2015 1,000s plants were found south of Middle lake in a discontinuous band under willow canopy and replacing native understory of Scirpus microcarpus, Cyperus eragrostis, and Persicaria punctata. False brome may eventually spread along San Francisquito Creek where it will join veldt grass (Ehrharta erecta), native to South Africa, in the forest understory of the Preserve’s broadleaf evergreen forest and redwood groves. MROSD. 2016. Ten-year Status Report and Recommended Continuation of a Slender False Brome [Brachypodium sylvaticum] Integrated Pest Management.
3 Briza maxima was first reported June, 1976 by Herb Dengler from the vicinity of Bear Creek.
4 Bromus hordeaceus in serpentine: Bromus hordeaceus was present in serpentine earlier than Spring 1962 [see Lolium note below] but evidently uncommon. Dengler writes in his fieldnotes of 21 May 1974, that soft chess “. . . seems taller than I recall it ever before, reaching better than 2ft on occasion. During grazing days [prior to April, 1960] B.m. [Bromus mollis] was rare on serpentine. Now it is abundant. Consequently wild flowers are fewer and sometimes stems necessarily longer.” In 1966 MacNaughton (1968) measured species rank by above-ground biomass in four serpentine plots on different slopes and aspects. Cumulative totals for two most abundant plants were Stipa pulchra 30% and Bromus hordeaceus 24.4%.
5 The Herbarium team removed a single plant from the Low Flow Crossing area of San Francisquito Creek in 2003. In 2005 ten or so Ehrharta erecta plants were observed fruiting in early December along Bear Creek and Sand Hill Rd at the Preserve boundary fence. Ehrharta can now be found downstream in and along Bear Creek and San Francisquito Creek and is also well-established away from the San Francisquito Creek around the Indian grinding rock near the beginning of Trail a and The Cave Trail.
6 Lolium multiflorum appears in all JRBP floras. With the transcription of the 1962/63 volume of Herb Dengler's field notes the earliest record to date has come to light. On May 19, 1962 Dengler wrote, evidently with reference to both Bromus hordeaceus and Loliu, "Mediterranian grass has successfully invaded the serp this year." (Brachypodium distachyon probably invaded serpentine post-1977.) Prior to the Dengler record we knew that Springer (1935) found Italian rye grass to be "frequent along roadsides and in open fields and on openly wooded slopes near roads." Thomas (1961) did not report Italian rye grass growing on serpentine in the Santa Cruz Mountains. McNaughton (1968), whose sampling was done in 1966, did not find Italian rye grass in his serpentine plots. In 1990 the third revised edition of the Jasper Ridge Docent Handbook still identified only soft chess from among the Preserve's naturalized grasses growing on serpentine. Armstrong and Huenneke (1993) documented Lolium to be common in serpentine in 1985-86 -- and that it was negatively effected by drought. In 2001 and 2002 Lolium accounted for 32% and 20%, respectively, cover of Stuart Weiss' JRBP serpentine transects (Weiss, 2002). In Spring 2006 the herbarium crew assisted in a repeat of the Armstrong and Huenneke transect and the vegetation component of a small mammal inventory. It is our impression that Lolium was dominant in many of the serpentine quadrats. Hobbs et al. (2007, p.554-45) data shows lower coverage and frequency of Lolium for 1983-2003 in his quadrats. The herbarium crew has not examined Hobbs' 50 x 50 m quadrats. Also see CNPS Vegetation Rapid Assessment Field Form JASP0001 3/25/2008.

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