Bloom Reports from the Anza-Borrego Desert: 2014-2015

Field of nearly-solid Sahara mustard in February 2010
Field of mostly-native annuals in January 2015
Pictures taken just northeast of the end of the pavement on Di Giorgio Road of approximately the same location.
Left: A field of nearly-solid Sahara mustard, Brassica tournefortii, on 23 February 2010 that had mostly wiped out the native annual display beginning in ~2007.
Right: A field of mostly-native young annuals on 22 January 2015. The previous three years of severe drought in this area (2011-2012, 2012-2013 and 2013-2014) mostly depleted the seed bank of Sahara mustard, allowing us to enjoy a native wildflower display once again here for at least a few years!
Click on the pictures for larger versions.

See also Pictures shown here on prior dates.

See Bloom Reports from the Anza-Borrego Desert for an introduction to this page, extensive general information (not specific to this year) about Annual Germination, Growth and Blooms, including what influences the duration and extent of the annual bloom, photo galleries, and links to other webpages giving information on Anza-Borrego Desert State Park Blooms.

Summary of Annual Germination, Growth and Blooms in 2014-2015

The incredible good news this year is that in the desert floor, the three years without significant rain here has apparently mostly depleted the seed bank of Sahara mustard, Brassica tournefortii, and it is mostly GONE on the desert floor!! See a map of the area where mustard is likely mostly-extirpated.

From his observations of weeded plots in the Mojave Desert, Chris McDonald had found that the seed bank was mostly depleted after three or four years. We had heard that, but found it very hard to believe until we saw it with our own eyes this year. Our Borrego Desert observations this year show that it does seem that three years is enough to kill most of the mustard seed bank in our area!

It has been depressing to have no annual germination on the Borrego Desert floor for three years, and we are well into a fourth year for areas east of Borrego Springs. But little did we know this was Nature's way of waving a magic wand to eliminate the mustard from many areas!

This year we have sparse to good annual germination in the Borrego Springs area and westward, including in areas such as the Hellhole Canyon Parking Lot (sparse; mostly under shrubs); the area south of the Visitor Center (decent, including out in the open); the desert sunflower sandy area along Henderson Canyon Road (sparse); the sandy area at the end of Di Giorgio Road (good); and Collins Valley above Lower Willows (good). In all of those areas, mustard is almost completely absent!!! There are still mustard seedlings here and there, but mustard is an extremely-minor component of the annual germination this year, whereas it was dominant before. Even filaree is not as abundant as it once was. Only Schismus is still abundant, but it is not dominant.

The absence of mustard is not due to any particular rainfall pattern this year. The non-native annuals of mustard, Schismus and filaree, Erodium cicutarium, are always the first of the annuals here to germinate, since they are adapted to a somewhat-different rainfall regime in their native land, allowing them to germinate with rainfall not heavy enough to germinate our native species. Hence if there was still a large viable seed bank of mustard, it would have germinated with or before our native annuals, as it always does.

The reason some mustard is still present in the immediate area of Borrego Springs is because there were some seeding mustards along roadsides in the last three years which replenished its seed bank there a little bit. Although we have had very little annual germination for the years 2011-2012, 2012-2013 and 2013-2014, what germination we did have was mostly these non-native annuals due to their lower moisture requirement for germination. The rainfall wasn't enough to germinate them away from roadsides; they needed the extra runoff from the road surface present along roadsides. Presumably, other areas with similar runoff, from buildings, boulders, hillsides or water channels will also have sparse viable mustard seed still present.

This depletion of the mustard seed bank also means that the area east of Borrego Springs, in the Borrego Badlands area, that was almost completely a sea of mustard by 2005 up to the north-south crest at the Thimble Trail, should now revert to being almost completely free of mustard the next time it rains enough there to germinate annuals. However, note that this is speculation, not observation, since there is no germination in that area so far this year.

So far, it doesn't look like we'll have annual germination in the areas east of Borrego Springs this year. We have found no annual germination east of the intersection of S22 and Rockhouse Canyon Road on the desert floor, including the Borrego Badlands, and no evidence of any significant rainfall in the sand. We have also found essentially no annual germination in Alma Wash and along Split Mountain Road. Bill Sullivan found no annual germination in Fish Creek.

Note that the mustard is mostly gone only from the desert floor east of Borrego Springs; there is still plenty of mustard in the higher elevations west of Borrego Springs, including Borrego Palm Canyon, and presumably also in the Santa Rosa Mountains north of the Borrego Badlands. But knowing that the seed bank lifetime is only three years means that any area that is kept free of seeding mustard plants for three years will no longer contain a viable seed bank of it! Hence all the mustard weeding that has been done by so many in so many areas is paying off more than expected at the time.

It obviously will be important to try to prevent the mustard from re-spreading into the desert floor in the future to delay as long as possible it taking over the Borrego Desert floor again.

See also more on why we believe the mustard has been extirpated from the Borrego Desert floor.

For germination, see a map of observed areas, where areas outlined in green have at least sparse germination and areas outlined in red have no germination, as of our last visit to each area in January 2015.

As for blooms, we are beginning to see the first winter annuals blooming; we saw the very first bloom of spectacle pod, Dithyrea californica, at the end of Di Giorgio Road on 22 January 2015. The number of plants and species in bloom should begin its usual increase soon. If the bloom increases as it usually does, as shown in the Plots of the Number of Species and Plants in Bloom On Each Trip: 2014-2015, by mid-February there should be about 50 species in bloom that can be seen on a single trip, compared to the ~25 species in bloom on 22 January 2015.

By the way, there is a new weed in town, Canary Island knapweed, Volutaria canariensis, that can germinate from monsoonal rains, and has been found in the thousands in each of the past two years in Borrego Springs. The highest weeding priority will be to extirpate this so that it can never become the next Sahara mustard. Frank Harris, from Seattle, has been waging a one-man war against this new species in his winter sojourns to Borrego Springs. But he is leaving at the end of January, and we desperately need someone in Borrego Springs to take over this fight.

Monsoonal Note. The low-elevation Borrego Desert (below 1000 feet) received significant monsoonal rain on 3 August 2014, and the desert transition area (1000 to 4000 feet) received significant monsoon rain in early July 2014. A number of monsoonal species in the desert transition area responded to the early July rains, and in some places large numbers of monsoonal annuals germinated from the 3 August rains.

The monsoonal annuals were in peak bloom on 2 September 2014, but were long dead as of January 2015.

See also:

Predictions for This Year

There will be at least some blooms in the area of Borrego Springs and west this year, but how good the bloom is depends on further rainfall. If we get no more rainfall, and the weather turns hot, the bloom will be meager. If we get more rainfall, and the weather stays cool, it could be a good rainfall year.

Stay tuned!

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Updated 25 January 2015