Hesperocallis undulata mass flowering - eastern California along I-10

oooOIOooo via pbs pbs@lists.pacificbulbsociety.net
Wed, 11 Mar 2020 20:30:03 PDT
Today I saw an enormous mass flowering of Hesperocallis undulata along Interstate 10 in eastern California, west of Blythe. There are hundreds of thousands of plants in synchronous flowering. Ford Dry Lake is north of the highway in this map view:


The site is between Desert Center and Blythe, about halfway between Los Angeles and Phoenix. It is about 3-4 hours from Los Angeles and 2 1/2 from Phoenix. The Beehive Ditch, crossed by I-10 and signed, was approximately the center of the population. There is a sign for an exit to Ford Dry Lake for hiking. It would be an easy day trip this weekend for people in metro southern California or Phoenix.

The highway cuts across a gentle sandy slope from the higher south down to the dry lake to the north. The plants are growing all along this slope. There are fewer on the south (higher) side of the highway; quite a few in the very wide median between the northbound and southbound lanes; and a very large number to the south of the highway, growing as far as my vision permitted me to see. I did not stop so I don't know how close they grow to the salty dry lakebed. In some areas the plants are separated by 2-3 meters in either direction, and in other areas there are at least 10 plants in an area of about 3 square meters. I would estimate there are hundreds of thousands of plants flowering, maybe more if the plants grow all around the dry lake.

The population extended for close to ten miles along the highway. To the east, the population gradually thinned out, but to the west, the terrain rises, and the plants stopped abruptly.

This plant has a vertical spike with sessile white flowers arranged in a spiral, rising from a sparse rosette of narrow, smallish, grayish green, thick and wavy leaves. They appeared to be close to a meter tall. Most plants had one inflorescence, but many had 2, 3 or even 4 inflorescences. All seemed to be at the same stage of flowering. The bottom few flowers had finished and the next rank of flowers above this was open. I don't know how long an inflorescence of this lasts, but they probably opened within the last few days to one week.

I have driven past this spot many hundreds of times in the past 40 years, at all seasons. I have never seen even one spike of this plant here. I didn't even know it is here. In Arizona it occurs sporadically in desert washes, or immediately adjacent to them. There are rarely more than a dozen plants in one area. The vast number of plants was an immense surprise.

Last winter/spring this area had more rain than this year, and the general flower display was even better. But there were no Hesperocallis last year. There are trails at Ford Dry Lake, and a weather station visible from the highway. I will try to look up the weather data. I wanted to post this as soon as possible.

The climate here is almost as hot as central Arizona in summer, and can get near freezing in winter. Rain is sparse on average and very erratic, mostly falling in winter. Summer rain is rare but can be torrential. A few years back the eastbound bridge over the Tex Wash just west of here was washed out during a summer thunderstorm, causing severe traffic problems for months.

Graduate students reading: Go camping this weekend! This is a great opportunity to get data for papers on pollinator studies, flower studies, and a chance to return over the next few weeks to study seed development. I don't think much is known about the pollinators of this plant.

Now speaking as a gardener, I have tried many times with seed from many sources to sprout this plant, always unsuccessfully. If the plants flower now, the seed will ripen during a very hot time of year. The seed is flat and black, like many Agave, Albuca, Hippeastrum and Yucca. There may not be any rain this summer, and even if there is, it will be sparse, and evaporate rapidly. When do these seeds sprout? There is little chance of plentiful water until next winter. Do they lie on the surface of the soil until then? Or do seeds expect a fair amount of summer water? Is this an ancient population stranded as the climate warmed and dried? The Sonoran Desert has had repeated warming and cooling cycles since the last Ice Age, with regions alternating between hot, dry desert and cooler, moister juniper savannah. However, now this plant is only found in the low desert.

I am not familiar with DNA work done with the plant, but... given its habitat, spike inflorescence, succulent gray-green sessile white short-tubed flower, and rosette of succulent long leaves, I wonder whether it's really an Agave?

I will try to return this weekend, and in the future, with a camera.

Leo Martin
Phoenix Arizona USA
Zone 9?

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