Plant Species of the San Jacinto Mountains
Portulaca halimoides, desert portulaca
Portulaca halimoides, desert portulaca
Bruce Watts, Tom Chester, and Lance Woolley
Table of Contents
Introduction
Photographs of Plants and Flowers
Distinguishing Portulaca halimoides and P. oleracea
Habitat
Geographic Distribution
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| Fig. 1.
Top Left: the "discovery" plant remnant found by Scott White on 15 October 2021, photographed by Tom Chester. This plant has already dispersed its seeds, from its circumscissile fruit capsule, of which only the lower half remains after the top of the capsule dehisced. Note the abundant hairs at each node in fruit. This plant was about 15 mm (1/2 inch) tall. Top Right: A live plant found by Bruce Watts and Lance Woolley on 14 August 2022, photographed by Bruce Watts. Note the cotyledons at the base, and the much less prominent hairs in the vegetative state. This plant was about 40 mm (2 inches) tall. Bottom: A live plant with flowers and fruit, showing the tiny flowers, a fruit capsule about to dehisce, and the fleshy leaves with a round cross-section, photographed by Bruce Watts on 6 September 2022. Note the tip of a pen for scale. See more of the pen by clicking on the picture. Click on the pictures for larger versions. | |
Introduction
Portulaca halimoides was not known from the San Jacinto Mountains until Scott White noticed an unusual short nearly-dead annual growing next to the Artemisia nova plants that he, Tom Chester, and Nancy Accola were surveying on 15 October 2021; see the left picture in Fig. 1, and Tom's iNat post.
P. halimoides is a fairly widespread species in the southwest, found in Baja California; eastern California; Arizona; Utah; and New Mexico; see its SEINet voucher distribution. It is also found in Central and South America; see the map from Kew. This species was first given its name by Linnaeus in 1762, from a specimen from Jamaica!
Before Scott's discovery of it here, it was only known in California from the Mojave National Preserve, and the northwestern part of Joshua Tree National Park (JTNP), with one voucher just barely in San Diego County from the Baja California population. Scott's discovery nicely bridges a gap between the JTNP plants and the Baja plants; expand the SEINet map to see that gap.
Due to its rarity in California, this species has a CNPS Rare Plant of 4.2, which means that it is "uncommon in California" and "moderately threatened in California". Unfortunately, this also means that its locations are obscured at iNat, even though there is little likelihood of any harm from presenting the actual coordinates.
There are a number of good reasons why no one had seen this species before in the San Jacinto Mountains. First, it is a monsoonal annual, so only appears as a live plant when there are sufficient summer rains to germinate it. Second, it is hot at its location in the summer, and hence few botanists are out looking for plants where it grows. Third, it appears to grow only in the same very restrictive habitat occupied by Artemisia nova, on the top of the Bautista Formation near the upper end of the Old Morris Ranch Road. Very few botanists or hikers travel in this area even when temperatures are pleasant. Fourth, it is a small plant, a "belly flower" with a very small flower that is not likely to catch anyone's eye. Scott noticed this plant while he was sitting on a boulder, during our survey for Artemisia nova. If we hadn't been doing that survey, who knows how much longer it would have been before this species was found here.
Since this was a new find, and its distribution was of interest, Bruce Watts decided to survey for this species after the good monsoonal rains in summer 2022. So far, Bruce has spent four days doing surveys, with Lance Woolley joining him for two of those surveys. The results are presented below.
Photographs of Plants and Flowers
Photographs of the vegetative plants and flowers are shown in Fig. 2.
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| Fig. 2. Top row: Flowers of P. halimoides. The leftmost picture shows three very tiny plants, with just 7 to 10 small leaves, with a single flower at the top. Click on the picture to see some even tinier plants not yet flowering. The rightmost picture shows one branch of a much bigger plant. Click on the picture to see more of that plant, with the center of the plant near the top of the picture, and a long branching stem on one side of the plant.
Bottom row: Left: a carpet of tiny seedlings. Right: a single larger plant just about to bloom. Click on the pictures for larger versions. | |
Seedlings of P. halimoides are very similar to seedlings of the cultivated portulaca, moss rose or sun rose, but their flowers are much smaller. Nonetheless, this plant is a little cutie. It has leaf axil hairs that add to its appeal.
Distinguishing Portulaca halimoides and P. oleracea
It is easy to distinguish these two species simply by the shape of the leaves; see Fig. 3 and photograph by Lance Woolley.
Fig. 3. Photograph from Tom Chester on 29 August 2022 showing both P. oleracea and P. halimoides. The two species are readily distinguished by their leaves. P. oleracea has flattish leaves widest near the tip. P. halimoides has terete leaves that are almost the same width throughout except for a slight tapering at their base and tip. Note the very young plants of P. halimoides at extreme right, and very young plants of P. oleracea at the extreme bottom in the middle.
Habitat
P. halimoides almost exclusively grows in depressions in the Bautista Formation that are relatively pristine and have few non-native plants. Those depressions hold the summer rain long enough to result in good germination of it and other plants. To find this species, first look for green areas like in the top pix of Fig. 4.
Area dominated by the non-native P. oleracea usually have no P. halimoides plants, but may very infrequently have a few plants.
Interestingly, P. halimoides is most abundant when it grows with Artemisia nova. Their geographic distribution here is very similar.
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| Fig. 4. Photographs by Bruce Watts from 29 August 2022 showing the habitat in which P. halimoides is found. Top: P. halimoides is mostly found in depressions that held the summer rain long enough to result in good germination of it and other plants. To find this species, first look for green areas like in the top pix. The second and third pix are closer and closer views, with several P. halimoides plants seen in the bottom pix.
Top: Click on the pictures for larger versions. | |
Geographic Distribution
Bruce Watts surveyed for P. halimoides on 14, 22, 27, and 29 August 2022, accompanied by Lance Woolley on the 14 and 27 August surveys. Bruce estimates the total number of plants is in the vicinity of 11,000.
The GPS points recorded by Bruce are shown in Figs. 5 and 6.
Fig. 5. Large scale map showing the GPS points for P. halimoides with geographic features labeled.
Fig. 6. Detail map showing the GPS points for P. halimoides. Locations with dense numbers of plants have larger symbols.