University of Alberta study maps growing conditions for native grasses at Edmonton solar farm

The University of Alberta reported on September 29 that a study at an Edmonton solar farm found sharply different growing conditions beneath and between its panels. The findings matter for developers trying to restore native grasses on solar sites: a seed mix suited to an open, sunny row may face different conditions in panel shade or where water pools.

Researchers examined seven seeded native grass species at EPCOR’s kīsikāw pīsim solar farm in the North Saskatchewan River valley. The site occupies former cropland in the Canadian Aspen Parkland. Their study followed early establishment over two years and measured how panel position and wetter or drier ground related to vegetation, weeds, light, soil temperature and moisture.

How shade and pooled water changed the Edmonton site

The researchers laid out 12 six-metre transects across ground beneath panels, partly lit panel edges and open spaces between rows. They also sampled drier ground and lower positions where water had pooled. That design allowed comparisons within one facility, where a restoration planting encounters several growing conditions rather than a single uniform field.

Sunny positions received 11.6 times as much light as positions beneath panels. Their soil was 3.2°C warmer and held 12% less moisture. The open positions had more than twice the plant diversity recorded beneath panels. Those figures describe differences at this site; they do not establish that more sun produces better native grass restoration overall.

What the results mean for native grass seed mixes

Open positions had more seeded native grass cover, but also more noxious weed cover. Two introduced perennial grasses, Bromus inermis and Poa pratensis, persisted across the sampled positions. That combination makes sunlight an incomplete guide to restoration: a place where planted grasses grow can also give competitors room to spread.

The paper discusses different responses among the planted species, including Festuca hallii, Nassella viridula, Hesperostipa comata, Pascopyrum smithii and Koeleria macrantha. Its detailed results found that several named species did not differ significantly by panel position. With native establishment still sparse, those observations offer limited guidance for assigning individual species to shade or sun. The shaded ground was hand-seeded while ground between rows was drill-seeded, so planting method could also have contributed to differences in establishment.

The authors propose considering seed mixes that include grasses suited to shade as well as drought, with choices tailored to positions beneath and between panels. They also discuss wider spacing between panel rows or mounting panels higher as possible design changes. The Edmonton study observed an existing planting; it did not test whether different mixes, row spacing or panel heights would improve restoration.

Why continued management matters

Study leader Fengxue Zheng said native grasses can provide soil stability, soil carbon storage, water infiltration and refuge for pollinators. The paper says former agricultural use, site preparation, weed pressure and the panel-created microclimates could hinder recovery. Continued weed control and monitoring may therefore be needed as planted grasses establish. Zheng called for adaptive management rather than one restoration method for every part of a site.

The study’s funding included Mitacs, EPCOR Water Services, the Alberta Conservation Association and Future Energy Systems; its conflict statement also reports EPCOR support to Zheng. Those relationships are relevant to readers assessing research carried out at an EPCOR solar farm. They do not change the study’s reported measurements or remove the need to test whether its proposed restoration approaches work over time.

What other solar sites can tell researchers

Conditions elsewhere need separate measurement. In an independent study of a Mojave Desert solar facility, U.S. Geological Survey researchers compared bare-soil spaces inside the facility with nearby undisturbed desert from June 2023 to February 2025. They reported higher soil moisture inside the facility, alongside higher subsurface soil temperatures. The desert comparison concerns another climate, facility and research question; it provides context for why a solar site’s effects cannot be reduced to shade alone.

For Edmonton, the immediate finding is a patchwork of light and water conditions alongside uneven early grass establishment and weed pressure. Zheng said longer-term studies are needed to learn how restored grassland develops. Whether a tailored seed mix or different panel layout leads to durable native grassland at this site, or works at other solar farms, remains untested by these results.