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Wild Buckwheat Varieties In Palomar Coastal Sage Scrub
© W.P. Armstrong (Updated 9 June 2024)   

The wild buckwheat (Eriogonum fasciculatum) varieties fasciculatum and foliolosum are defined differently in Munz and Jepson. As a result, botanists may key the same specimens to different varieties, depending on whether they use Munz or Jepson. This is especially true if one uses the key in Beauchamp, in his Flora of San Diego County. I have struggled with this confusion for decades while teaching my Plant Identification course (Botany 110) at Palomar College.

The best explanation for this controversy is published online by Tom Chester: "After studying these plants, and because of all the weasel words (generally & + or -) in the JM descriptions and key, we primarily key on the involucre hairiness to separate these two varieties. If the leaf is glabrous above and the involucre is glabrous, we key such plants to var. fasciculatum, even if the perianths are a bit hairy outside, due to the perianth (+ or -) glabrous in the JM description for that variety. If the involucre is hairy, we key such plants to var. foliolosum. So far, whenever we have seen a hairy involucre, the leaf upper surface and perianth has also been hairy." See Tom's complete explanation at the following link:

  Tom Chester's Buckwheat Variety Comments  

Regarding varieties foliolosum & polifolium: Tom Chester has noted that these varieties merge into each other on the Palomar Mountain Dripping Springs Trail. Lower elevations have var. foliolosum, and higher elevations have var. polifolium. There is a 0.4 mile stretch of trail in which the plants gradually change between the two varieties. Tom and botanist Jane Strong have even seen plants in the San Gabriel Mountains that would key to var. foliolosum in the spring, but var. polifolium in the fall!

I have included the following images (May-June 2024) from coastal sage scrub north of the Cactus & Succulent Garden.

According to Eriogonum key in the Jepson Manual, we may have 3 varieties of Eriogonum fasciculatum in the coastal sage scrub between Arboretum & Cactus Garden. Robert Kurner reported var. fasciculatum, var. foliolosum and var. polifolium. I knew there was considerable variability in our local wild buckwheats, but I only had var. foliolosum on my original checklists. Intergradation between these varieties always made their precise identification difficult on my numerous Botany 110 field trips throughout San Diego County.

There are possibly 2 varieties of Eriogonum fasciculatum in this photo. The low plants in foreground resemble var. polifolium according to botanist Robert Kurner. The taller plants in distance may be var. foliolosum.

The following 2 images fit Jepson description of var. polifolium.

Var. polifolium in Jepson key: Lvs gray-hairy on both surfaces or densely gray-tomentose abaxially, gray-hairy adaxially, margins not or occasionally rolled under.

The following 4 images fit Jepson description of var. foliolosum.

Var. foliolosum in Jepson key: Lvs densely white-tomentose abaxially, sparsely tomentose adaxially, margins gen tightly rolled under (revolute). Just north of Cactus Garden along dirt path. I included image of this plant that most certainly does not fit var. fasciculatum; however, there are other plants in coastal sage scrub that appear more like var. fasciculatum.

2 More Images of var. foliolosum

Eriogonum fasciculatum var. fasciculatum

Var. fasciculatum in Jepson key: Leaves thinly white-tomentose abaxially (lower surface), glabrous adaxially (upper surface); flowers, involucres generally glabrous (may have a few minute hairs); plants gen decumbent (with some horizontal branches).

The following images fit the Jepson description of var. fasciculatum; however, there are a few hairs on perianth and bracts below involucre. It sort of fits "generally glabrous" in Jepson. Now I know why I just called it Eriogonum fasciculatum and ignored the variety during my teaching career. This may explain why I moved to ant photography during my retirement.

This is about as close as I can get to a single involucre. There are a few minute hairs on involucre barely visible in image; however, it is essentially glabrous. Based on Tom Chester's detailed observations, I must conclude that these varieties are not always that easy to separate and may exhibit intergradation. In the meantime, I must remain humble and open minded. [BTW, the following image near my home in Twin Oaks Valley fits the Jepson key to var. fasciculatum almost perfectly.]

  Ants of Twin Oaks Valley  

Addendum

As I was writing this page, I decided to check the wild buckwheats near my home in Twin Oaks Valley. Along nearby Twin Oaks Valley road I found var. foliolosum with distinct hairy involucres. This variety is widespread throughout coastal sage scrub in San Marcos. To my surprise, the ones on my street had glabrous involucres characteristic of var. fasciculatum (see following image)!