Plant Species of the Borrego Desert: Poaceae:
Stipa capensis (= Stipellula capensis), spear needlegrass
Stipa capensis (= Stipellula capensis), spear needlegrass
Tom Chester and Don Rideout
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| Fig. 1. Spear needlegrass in Murray Canyon, one of the Indian Canyons west of Palm Springs, on 6 April 2011. Left: Spear needlegrass stuck in Kate Harper's pants. Right: A field of spear needlegrass, that used to be a field of flowers.
We don't want this to happen in our Borrego Desert! Unfortunately, its invasion of our desert has already begun, being first detected in 2023, after probably being here for at least two years previously. Click on the pictures for larger versions. | |||||||||||||||||||||||||||||||
On 6 April 2011, Tom was horrified to see a new invasive weed that had taken over some areas of the Indian Canyons west of Palm Springs. "Mountain Bob" Hepburn had been complaining for several years about this grass crowding out the wildflowers in Tahquitz Canyon, and noted that it really exploded in 2011.
This grass was first discovered in California in 1995 in Chino Canyon, below the Palm Springs Aerial Tramway, by Andy Sanders. It had spread so much there in just six years that in 2001, fire burned 1000 acres (400 ha) of "mostly S. capensis" there. Four years after that, in 2005, Richard Minnich reported an "extensive cover of S. capensis in Chino Canyon", and there were few native wildflowers there, despite that being a glorious year for desert wildflowers elsewhere. (See CAL-IPC Stipa capensis plant assessment form.) Most sources, including the Jepson eFlora, call this plant Stipa capensis, but iNat uses a newer name of Stipellula capensis, defined in 2012.
Clearly, this weed can increase its population numbers rapidly. Worse, it can be transported long distances because its seeds are easily picked up by hiker's boots, clothing, and presumably animal fur. "Spear needlegrass", and "speargrass", are very appropriate names for this species. Other common names for this plant are Cape ricegrass, Mediterranean steppegrass, and twisted-awned speargrass.
Tom has been worried about this grass spreading to the Borrego Desert ever since then, and 12 years later his nightmare came true. Carla Hoegen and Fred Melgert found a small population at the high point of the Alternate Trail in Borrego Palm Canyon on 14 March 2023, and posted it at iNat on 15 March 2023. Travis Columbus, the author of the Jepson eFlora treatment on Stipa, kindly quickly confirmed the determination on 16 March 2023. Travis gave the tip that in California, this is the only Stipa, needlegrass, species, that is an annual, making its identification quite easy.
The next day, on 17 March 2023, the two authors of this page, Tom Chester and Don Rideout, went on a search-and-destroy mission in Borrego Palm Canyon. We were expecting perhaps 30 plants or so, hoping that this was a first or second year infestation, but it turned out there were at least 300 plants. It seems likely that the first plant appeared here at least two years ago and it was spreading, un-noticed, on the most popular trail in Anza-Borrego Desert State Park.
It appears this grass has also recently spread to the coast at Pt. Mugu.
This page reports our survey results.
Locations of the Plants and our Survey Track. We found plants in only two locations. All the plants except one were found at or very near the high point of the Alternate Trail. The lone disjunct plant was found 100 m (335 feet) farther along the Alternate Trail as it descends to the Parking Area.
You can download GPX files of the GPS points for the plants, and for our entire survey track.
Fig. 2 shows a Google Earth view to the west from above the parking lot for the Borrego Palm Canyon Trail showing the trails, drainages, and Stipa locations. See also a Google Earth view with north up showing the entire area (We didn't survey the lower part of the Main Trail, so part of the Main Trail is not covered by the blue line).
Fig. 2. Google Earth view to the west from above the parking lot. The pink dots show locations of Stipa capensis. The blue line shows our survey route on 17 March 2023.
Fig. 3 shows a detail view of the main population.
Fig. 3. Google Earth map view, with north at the top, showing the main population of Stipa capensis, the pink dots. Not every plant was GPS'd, which probably would have mostly or completely filled in the area inside the extent of the largest part of the distribution. Many of the GPS points were inferred from Tom's track, where the track was stationary from his weeding; Don's weeding areas were not recorded.
The blue line shows Tom's survey route on 17 March 2023. Don explored additional area below the western part of the main population to delineate its extent there; his track is not shown. At this scale, the GPS tracks are not precise, primarily due to multi-path error in the satellite signals due to reflections from the abundant rocks here. The single plant not on a track was found by Joe Woods earlier on the same day.
Google Earth "floats" the markers a bit above the ground, so they sometimes appear slightly north of our survey track in this map.
The population extent is 25 m (85 feet) east-west, and 15 m (45 feet) north-south, not including Joe's plant.
Number of Plants. All of the plants except one were in the main population found at the location of Carla and Fred's plants. For that main population, we did not count every plant, since we concentrated on removing the plants, not recording their numbers. After finding the extent of that main population, Tom stood on a rock at a good vantage point (see Fig. 6 below), and quickly counted all the plants with a mature inflorescence by counting them in groups of 5 or 10, which totaled 130 plants. Then, when we started weeding, it was clear there were at least as many plants without a mature infl, so we doubled the estimate to 260 plants. As we got further into the weeding, we found a number of young plants hiding inside other plants, so we estimated there were at least 300 plants. There could easily have been more, since we spent something like 30 minutes actively weeding, and at times we were each pulling out one plant per second.
Areal extent of the population. Using Google Earth, the minimal area polygon of the contiguous main population contains 190 square meters (2,000 square feet). The perimeter of the polygon is 75 m (240 feet). There were two isolated plants found just below the main population, one 5 m (15 feet) away, and another 10 m (30 feet) away.
One isolated plant was found 70 m (240 feet) due south of the main population. That plant is a distance of 100 m (335 feet) along the trail between the populations.
Recommendations for follow-up surveys. We strongly recommend follow-up surveys in the next few weeks, since some plants are inside shrubs, and are only visible when they put up their inflorescence. We removed a number of plants that had not yet put up an inflorescence, but which were easily identified by their robustness compared to Bromus rubens. In addition, follow-up surveys need to be done in areas we did not survey, including the area above the main population; the adjoining major drainage south of the main population; and in additional areas below the main population.
Photographs of our plants from our survey, and from others, showing the plants and the habitats in which they were found, are posted at iNat. The plants seem to grow in every possible habitat, from flat ground to hillsides, in sand, soil, or cracks in boulders. At Tahquitz Canyon they also grow along streambanks. The most detailed photographs of the plants, along with measurements from a voucher they took, are from Carla and Fred's initial observation.
Survey Details.
We began our survey by going up the Main Trail to the junction with the drainage coming from the high point of the Alternate Trail, and then followed that drainage uphill; see Fig. 2. Carla and Fred's observation was right next to that drainage, so we wanted to check for any Stipa plants that had washed down that drainage.
That drainage has several upper branches. It turned out we followed a southern upper branch to the Alternate Trail, and we were surprised that we immediately found a single Stipa plant there. That did not bode well.
After removing that plant, we then surveyed down the Alternate Trail for 0.1 mile to look for more along the trail. We found none, so turned around and went back up the Alternate Trail to Carla and Fred's location.
There our jaws dropped. Instead of the ~50 plants we expected might be here, there were vastly more; see Fig. 4 for part of the field we saw.
Fig. 4. Our first view of the main population of Stipa capensis. Click on the pix for a larger version.
Our first task was to map the population there as best as we could, consistent with leaving enough time to remove this population, and for us to survey the rest of the trails in Borrego Palm Canyon. Don headed down the drainage shown in Fig. 4, and I headed down one of the several use trails immediately north of there, since we had found Stipa there as well. We met up farther down the use trail, and were relieved to have found only a single plant in that area. Tom's track in that area is shown in Fig. 3, as two of the three blue lines in the lower right of that map. Note that we would have missed Joe's plant in our survey, so additional surveys should be done in the area south of the population. In addition, more surveys should be done in the area north of the population.
When we completed our initial mapping, we began removing plants. Tom didn't think it would be possible for two old folks like us to remove all the plants, since we both have backs that complain if we do too much weeding. Fortunately, we quickly learned that it was exceptionally easy to remove most of the plants. Since these were annuals, in sandy / gravelly soil, all it takes is one little tug to pull a plant out of the ground. Most of the time, we didn't even have to shake off any dirt or sand attached to the roots! Tom's concern quickly moved from his back to worrying about repetitive strain injury to his arm from all the yanking. (:-)
We began by removing the outlying plants, since that would make it easier for anyone to remove plants left unweeded by us if they were all in a small area.
We spent just under an hour weeding, and were able to remove all the plants we found. Fortunately, they just barely fit in the kitchen trash bag I had brought; see Fig. 5.
Fig. 5. Don is holding the kitchen trash bag stuffed full of Stipa. The other people in the picture delineate the Alternate Trail in this area. Note the large number of inviting boulders for hikers to sit on to remove things like Stipa seeds from their pants, socks, or boots. Click on the pix for a larger version.
Fig. 6 shows a "before and after" pix of the main concentration of plants.
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| Fig. 6. Area with the main concentration of Stipa, before weeding (left) and after weeding (right). Click on the pictures for larger versions. | |||||||||||||||||||||||||||||||
Since Carla and Fred, and the Park botanists, had asked for specimens to produce vouchers, and because we didn't want to lug that bag around the rest of our survey, we hustled that bag down the Alternate Trail to the car, where Fred picked it up while the plants were still fresh.
We immediately returned to this spot, this time taking one of the use trails up to survey them for more Stipa. We found none there.
We trepidatiously continued surveying along the Alternate Trail toward the Palm Grove, worried that we might find an even larger population "just beyond the bend". Fortunately, we found no additional plants along the Alternate Trail, nor on the main trail.
For completeness, we surveyed down the raging Borrego Palm Canyon Creek almost to the ABDSP property line, crossed the Creek after all of its water had seeped into the sand, and returned back to our car. No additional plants were found, which was wonderful news.
We thank Carla Hoegen and Fred Melgert for finding this grass, and alerting us to its presence.