By Dennis Albert, PhD Sr. Research Faculty
Horticulture Department, Oregon State University
The shorelines and shallow waters of many of eastern Oregon’s shallow alkaline lakes contain a distinctive flora that has been incompletely explored. These plants appear as water levels in the lakes begins to drop in May, and many have flowered and begun to dry up by mid to late June. We had hoped to explore at Malheur Lake for some of these early plants, like playa phacelia (Phacelia inundata), Bach’s calicoflower (Downingia bacigalupii), and tansy leaf evening promrose (Taraxia tanacetifolia) that we had found at Hart in earlier surveys between 2012 and 2016 at the Warner Lakes and Hart Mountain Antelope Refuge. All these plants are adapted to the harsh conditions of the playa lakes. Long tap roots allow these plants to reach water deep in the soils as water levels rapidly drop in the early summer heat.
Since almost all these plants are annuals, they are able to grow rapidly and produce seeds before drying up and dying by late June or early July. And most playa plants are short in stature, hugging the ground rather than growing vertically in a landscape where strong winds can occur almost daily. Several playa plants, including Bach’s calicoflower, support endemic ground-nesting bees whose life cycles are linked to the annual flood and dry down cycles of the playa lakes.
Logistical problems resulted in postponing arrival in 2022 until early September, so I was unable to search for these spring and early summer annuals. Instead, I focused on a different group of late season plants that are also concentrated along the moist margins of the playa lakes or streams. Most are much less showy – grass, sedge, or submergent plants. One that I had hoped to find was the 1-inch tall Colorado spikerush (Eleocharis coloradoensis), a plant first found in Oregon along the shores of the Warner Lakes in 2018. On my second day of searching at Malheur, I found thousands of plants growing in the muddy delta where the Donner and Blitzen River flows into Malheur Lake.
Unlike most of the spring flora, many of these sedges and grasses, including Colorado spikerush, are perennials, with roots and underground stems (called rhizomes) that form a dense turf below the muddy soil surface. This network of fine roots and rhizomes are quite resistant to wave action and the flowing stream waters, thus reducing erosion. Colorado spikerush has rhizomes that connect several stems together, but are no thicker than a fine thread. It also has tiny dark brown to black tubers that can remain dormant through the dry summer or periods of drought, producing new plants when moisture needs are met. Colorado spikerush along the edge of Malheur Lake grows with another small (1-2 inches) but showy plant, yellowseed false pimpernel (Lindernia dubia), which also produces a dense turf of fine roots and intertwined stems.
Another interesting new plant to the refuge is a submergent plant, California waterwort(Elatine californica)(8), found growing in Benson Pond. California waterwort’s flower is only 2 mm (1/8th of an inch) across, but is distinctive, having four small pedals and forming a capsule also divided into 4 parts (See photo). Plant surveys of a few of Malheur’s ponds were rushed but demonstrated that they support a diverse submergent flora worthy of more focused surveys.
In all, during just two long days of plant surveys, we found 35 plant species that had not been documented previously at Malheur, Harney, and Stinking Lakes, as well as a few small ponds on the refuge where the field surveys were concentrated. A spring survey would almost certainly double the number of new species for the refuge. One genus of plants that was well represented was spikerush
(Eleocharis), which had at least 7 of the 17 spikerushes known from the state. All of Oregon’s spikerushes occupy moist soils along streams, wetlands, or lake edges, so it is not a great surprise that the Malheur refuge supports a rich spikerush flora. Most of the late season plants produce abundant seed or vegetation fed on by migrating waterfowl.
I’m looking forward to a spring and early summer plant survey in 2023. There is extensive unexplored habitat for both early and late season plant exploration at the mouth of the Silvies River, where Warm Springs Creek meets Harney Lake, as well as in ponds within the refuge.
I would like to express my appreciation to the Malheur Wildlife Refuge for providing me with housing, and to Alexa Martinez, Malheur NWR wildlife biologist, and Rebecca Pickle, aquatic health technician, for identifying sites for surveys and for assisting me with transportation to these sites. Thanks also to Oregon Flora for providing access to plant photos for inclusion in this report.