Pink-margined Monkeyflower Rare Plant Treasure Hunt

Horse Mountain Botanical Area June 20, 2015

Pink Showy MonkeyflowerFor the third time in as many years, Six Rivers National Forest has partnered with the North Coast Chapter of the California Native Plant Society (CNPS) to host a Rare Plant Treasure Hunt. The Rare Plant Treasure Hunt (RPTH) is a citizen-science program started by CNPS in 2010 with the goal of getting up-to-date information on many of our state’s rare plants, while engaging chapter members and other volunteers in rare plant conservation.

On June 20, 2015, nine chapter members including 3 Forest Service botanists, headed up to Horse Mountain Botanical Area on the forest to visit known sites of the pink-margined monkeyflower (Erythranthe trinitiensis). This species was recently described in 2013 and won’t be found in the most recent edition of the Jepson Manual, which was published a year before. It is an annual known only from Humboldt, Siskiyou and Trinity Counties. It is listed in the Inventory as a 1B.3 and its global ranking is 2. It is believed to be endemic to serpentine substrate. Additional information regarding this new described rare plant can be found at the CNPS website.

Perhaps you are wondering why a monkeyflower is not in the genus Mimulus—it’s due to a recent revised taxonomic classification of the Phrymaceae, based on molecular analysis and morphological taxonomic studies. How to keep up with the many changes in plant nomenclature that are on the horizon is a bigger question for those of us who are memory challenged and will always think of a monkeyflower as a Mimulus. You will be happy to hear that the pink-margined monkeyflower can be identified by field observation.

The pink-margined monkeyflower is quite showy having a red spotted yellow floral tube, becoming white as you approach the pink tips of the flower. However, the flowers are quite small, easily under a centimeter in diameter, and are best appreciated using a 10x hand lens. The plants we observed were mostly under 2 cm tall and hence they are very easy to overlook. At first we walked right by a known site before finally finding some and honing in on our search image. The pink-margined monkeyflower is truly a “belly plant” and the flowers are best observed by lying face down in the road with hand lens in hand remaining ever alert for oncoming vehicles.

Except for a handful of plants found on the cut slope of the road to the old ski area, the majority of the approximately 250 plants found were growing on the uphill moist surface of gravel roads at the base of the cut slope. The compacted road substrate was still moist, a condition favored by the pink-margined monkeyflower and it seems likely that snow melt plays an important role in the persistence of this short-lived annual. Although the sparsely vegetated gravelly road edge appears to provide a degree of freedom from competition and favorable conditions for seed germination it is important to find populations off of roads in order to observe it under natural conditions. The importance of snow melt heightens the concern regarding climate change and the impact reduced snowfall could have on the persistence of the pink-margined monkeyflower on Horse Mountain necessitating a revisit in early June 2016—mark your calendars for June 11, 2016!

2015 Rare Plant Treasure Hunt group

Other species of interested observed at Horse Mountain include: Cirsium cymosum var. cymosum, Epilobium minutum, Carex sp., Triantha occidentalis, Lilium pardalinum, Cypripedium californicum, Eriophorum crinigerum, Antennaria suffrutescens, Hieracium greenei, Eriogonum nudum, Spiraea splendens,Toxicoscordion micranthum, Lomatium tracyi, Plantanthera sp., Hastingsia alba, Hosackia oblongifolia var. oblongifolia.