Olneya tesota, Desert Ironwood:
The 1,000 Desert Ironwood Trees north of Agua Caliente County Park
The 1,000 Desert Ironwood Trees north of Agua Caliente County Park
Walt Fidler, Tom Chester, Don Rideout, Carla Hoegen, and Fred Melgert
Fig. 1. One area of the Ironwood grove north of Agua Caliente County Park looking northwest. Photo by Don Rideout taken on 18 December 2023. Click on the image for a larger version that shows the original photograph. See also a a view approaching the main grove from the south by Don Rideout.
Olneya tesota, Desert Ironwood, is an iconic plant of the Sonoran Desert, with geographic limits that closely match the outline of the Sonoran Desert (Shreve 1964). It is a beautiful tree with dense foliage that is very recognizable from a distance. The foliage is gray-green to blue-green up close, but the trees can appear a dark green from a distance.
Ironwood has beautiful flowers as well, but most people don't get to see them, since it mostly flowers in May and June, long after most people have left the desert due to high daytime temperatures.
One of the densest locations for Desert Ironwood in the Borrego Desert is the bajada north of Agua Caliente County Park, where we have found a minimum of 1,039 Ironwood plants. Fig. 1 shows one view of the happy Ironwoods in that area. See also observations of Ironwoods from this bajada posted at iNat. As of 21 December 2023, there were 134 observations, with 132 from Fred Melgert and Carla Hoegen.
Our minimum number of 1,039 Ironwood plants is from the following surveys:
- On 27 March 2023, Walt GPS'd 747 Ironwood plants in this area.
- On 18 December 2023 Walt, Tom, and Don counted 659 trees visible from a route through the heart of the Ironwoods. See a map showing our survey route (blue line), and our estimated sight distance (white line), plotted with GPS points from Walt as of 18 December 2023.
- Carla Hoegen and Fred Melgert posted 132 iNat observations of Desert Ironwood in this area.
- On 19 December 2023, Walt GPS'd 142 additional Ironwood Plants, mainly in the northernmost area of the Bajada, which had only had two locations before, from Carla and Fred.
There are 376 Walt GPS points outside of the counted area, and four additional Carla and Fred locations, making a total minimum count of 1,039 Ironwood plants. In addition, Walt observed nine plants in the northernmost area of the Bajada that were inaccessible, and thus he wasn't able to take a GPS point for them in the field. Adding those nine plants makes a total minimum count of 1,048 Ironwood plants.
There are an additional 150 Ironwoods in Ironwood Canyon and Wash to the east.
In our 18 December 2023 survey, essentially all of the Ironwoods looked very happy and lush with foliage. The only exceptions were a few Ironwoods that were lowest on the Bajada, but above the Vallecito Wash, where we found several dead trees, and a handful of trees with a large number of dead stems.
The GPS locations of Desert Ironwoods from Walt, Carla and Fred are shown in Fig. 2.
Fig. 2. Geographic distribution of Olneya tesota, Desert Ironwood, showing individual GPS observations in Google Earth. Red circles are from GPS points taken by Walt Fidler; magenta circles are from iNat observations from Carla Hoegen and Fred Melgert. Blue and pink circles at extreme upper right are in Ironwood Canyon. Those Ironwoods are not included in the count here.
This image is looking just a big east of north from a vantage point at 5116 feet elevation above Agua Caliente County Park. Vallecito Wash runs mostly east-west along the bottom of the image.
In the linked image, the wash at middle right that leads to Ironwood Canyon was surveyed by Walt, and no Ironwoods were found.
See also a closer view into the main population of Ironwoods.
Click on the image for a larger version.
Fig. 3 shows that these Desert Ironwoods can readily be seen from County Highway S2 even though most of them are a bit over a mile away from the highway.
Fig. 3. Cropped normal camera view showing, in the distance, the Ironwoods on the bajada from the north side of County Road S2. The main grove is in the center of the image, with isolated plants on the bajada closer to the camera. The line of Ironwoods going up the drainage on the right is evident as well. The plant locations seen in this camera view match well the GPS locations shown in Fig. 2.
The sandy area in the foreground with scattered creosote bushes is just east of the Airstrip, and Whale Peak is on the horizon.
Photo by Tom Chester. Click on the image for a larger version that shows the original photograph.
See also a zoom view of the main grove by Don Rideout.
