Author: Tuula Rebhahn

In fall of 2022 RNPP measured out a couple of vegetable-garden sized squares of bare earth along the Rogue River and initiated the trial of a specially blended riparian seed mix. 

Our goal? To learn how to best apply native seeds to revegetate sites that have been smothered by invasive plants and treated with herbicide for over a decade. 

Project background and site prep were covered in the first blog post in this series, but to recap: At these two garlic mustard “demonstration sites”, we put down a native seed mix that contains species that do well in shady riparian areas. After the seeds have germinated, we will monitor the seeded areas for species diversity and compare them to “control” area where no native seeds will be added. We predict that the results will show a better coverage of native plants on seeded areas. 

At both the John Day Rd. site and the ODFW site, blackberry and garlic mustard have long suppressed natural regeneration of native plants. Garlic mustard itself is allelopathic, preventing native seeds from germinating. Finally, some of the treatment methods used involved broad-spectrum herbicides sprayed across all vegetation at the site, meaning only overstory trees survived. 

In this blog post, we will discuss the seeding mix and methods used at the demonstration sites, as well as a new seeding technique we’re excited about involving divots!

Seeding Strategy Overview

The scope of this project is not to revegetate all of the 100+ acres that have been affected by garlic mustard. Instead, the goal is to trial a specialized native seed mix and seeding strategy that can achieve some of the land management goals at the site (stabilize soil, prevent new invasives from moving in, provide habitat), and can be applied to larger areas in the future. 

The “demonstration sites” where this seed mix is being trialed measure 10×20 meters (roughly 32×64 feet). These plots are divided into two “treatment” areas (seeded) and two “control” areas (unseeded). 

Species Selection 

To choose which species to include in this seed mix and begin restoring native plant diversity to the treatment areas, we first had to consider seed availability. We knew we wanted to “go heavy” with a large number of seeds per square foot, to give the plants a better chance at competing with invasives. We also anticipate some herbicide drift occurring through continued spot-spraying for garlic mustard and other weeds, resulting in some unintended die-off of young native plants. 

Through the Rogue Native Plant Partnership, we were able to secure seeds for 19 different species in large enough quantity to be sown over an area totaling 1/10 of an acre. Most of the seeds used were collected in the wild around the Rogue basin, and some came from locally farmed seed lots. Availability also determined the ratio of forb, grass and woody species seed; while we have access to plenty of milkweed seed, woody plant seeds are not so abundant. 

We also spoke with the herbicide applicators who have worked at these sites for years. Their observations were valuable for learning what species have come back naturally in some of the areas sprayed for garlic mustard. These included some of the grasses used in the mix. 

Combining this intel with general knowledge of the species that compose riparian understory communities in the region, we came up with the following species list: 

Some of these species were also chosen for their ability to grow quickly and compete with invasive plants, for instance, lupine, snowberry and tarweed. 

Seed Mix

To create the seed mix shown in the graphic above, we used the seed mix calculator linked to in this blog post. That post has a detailed discussion of how to determine your seeding rate, taking you from a species list in-hand to a calculated seed mix with a balanced proportion of each species – we highly recommend it!  

For this demonstration seeding we determined that a fairly high seeding rate, 100 seeds/square foot (or 72 lbs/acre) would be most effective. 

Prepping & Seeding

As described in the first blog post in this series, the areas to be seeded had been treated for weeds before we arrived. That’s ideal for restoration planting – because native plants do not compete well with invasives, pre-treatment is needed.

To improve soil contact with the seeds, we raked the entire demonstration site (plot). Then we checked our measuring tapes to mark out the “control” (no seeds) and “treatment” (to be seeded) sub-plots. These sub-plots alternate because environmental variations like topography and shading from overstory trees on one end of the plot or the other could bias our results, and we wanted to reduce that bias. The alternating sub-plot layout is shown in Figure 1. 

Having checked our layout and measurements, we proceeded to the treatment sub-plots to make our divots and sow the seed. 

Divots? What are divots?!

Divots are small impressions in the earth that mimic the footprints of a large animal like an elk (which roam the riverbanks around our demonstration sites). The technique was developed for seed-based restoration projects in the harsh arid environments of the US southwest (Bainbridge, 2007). The theory is that by placing seed in the divots, the seed is less likely to be blown away by wind or washed away by rains, while the divots may help protect the seed from drying wind and sun. The technique has been used on other projects here in southwest Oregon with successful results. 

For these demonstration sites, we used a hoe to make small impressions in the soil (no more than ½ inch deep), spacing them about a foot apart. A total of 50 divots were created in each 5×10 meter subplot, and a handful (about 1/10th of an ounce) of seed was added to each divot. 

Finally, we raked each seeded sub-plot lightly again to provide some soil coverage to the seeds while maintaining the divot structure. 

Now, We Wait

Habitat restoration with native seeds takes time; while it may look like nothing is happening on the surface, all winter long, seeds are responding to a thousand subtle environmental messages that allow them to germinate at just the right time. If conditions are right in spring of 2023, those seeds will send small leaves toward the sun. If conditions don’t align for growth, these seeds will bide their time until a future spring. 

The benefits for those hoping to restore landscapes with native seed is that dollars spent on seed, when it is planted at the right time and with good attention to site preparation, is rarely wasted. Even if only half of the species placed in these demonstration sites as seed develop into mature plants, the result will be higher species diversity than if we had relied only on planting starts or plugs available from native plant nurseries. And, at $14/oz* of seed versus $2-$20 per individual plant plug, our restoration dollars are stretched further. 

Stay tuned for the next blog post in which we’ll reveal our monitoring results and lessons learned from this project. 

*2022 price for seed mix; individual species/lot prices vary widely

In the midst of Cherry Blossom Madness in Washington, DC, a contingent of Oregonians landed to be among “our people”: Seed (but never seedy!) People.

The theme of the 2023 National Native Seed Conference was “Cultivating the Restoration Supply Chain”. In the past few years, we’ve all become all too familiar with the term “supply chain” in the context of supply shortages. In the restoration world, the supply chain doesn’t just involve farmers, distributors, native seed partnerships and administrators, though all of these people are important. The most important “people” involved in habitat restoration are plants – the source of all those vital genetic information packages that we know as seeds.

Best practices in habitat restoration say to use locally genetically adapted seed for revegetation of degraded landscapes; however, in many parts of the US and the world, locally adapted seed is simply not available, or it is so scarce as to be unaffordable. The National Native Seed Conference (NNSC) convened to clearly define the barriers to building a more abundant native seed supply chain, and to explore some possible solutions.

Rogue Native Plant Partnership was able to participate in this conference thanks to the generosity of the Institute for Applied Ecology (IAE), who sponsored Tuula Rebhahn and Vanessa Robertson-Rojas to attend. Funding from RNPP partners Confederated Tribes of the Siletz Indians sent a third delegate, Kathryn Prive. Tuula and Kathryn coordinate the RNPP through its fiscal sponsor, The Understory Initiative, and Vanessa is an Ecologist with The Understory Initiative who manages several native seed farming contracts in the Rogue Basin.

Safe from crowds of selfie-taking tourists in a conference hotel just downriver from our nation’s capital, the three of us, along with 500 other conference attendees, were treated to a blossoming show of a different sort. A gorgeous diversity of flower photos accompanied many charts and graphs compiled by researchers, farmers and restoration practitioners, magnified by powerpoint projections. For three days we took in dozens of rapid-fire presentations to learn about all aspects of the seed supply chain. With partners at IAE and US Fish & Wildlife Service, we also facilitated a symposium on Oregon’s native seed partnerships, and Vanessa presented research by The Understory Initiative into the efficacy of planting natives beneath solar panels (a recording of the symposium presentation will be available soon and shared via the RNPP Newsletter).

Needless to say, we learned a lot, and the value of putting faces to names, and bodies to floating heads on the Zoom calls of the past three years, is immeasurable. To distill all of the information, insights and “ah-ha!”s into a neat written package is probably a fools’ errand, but we would like to try anyway.

Here are our takeaways from NNSC2023.

1. We Are Not Alone

There’s probably not a single person who hasn’t felt a sense of laboring in isolation over the past three years, whether physically or conceptually. But in the process of preparing for the conference and in the days we spent networking, we recognized that Seed People are everywhere – in Oregon, across the US, and even globally. We counted eight partnership-type groups in Oregon that coordinate native seed production, distribution and application in our state alone. Seed partnerships are “sprouting up” in the northeastern US, Arizona, Nevada, California, Iowa, Wyoming and Hawaii. We even talked to a seed farmer from Germany. In all of these groups, we heard about similar challenges: 1. Convincing farmers that growing native seed is financially viable; 2. Finding reliable sources of information about how to grow native plants that are not commercially produced; and 3. Sourcing the foundation seed from the wild in areas where there are precious few intact native plant communities left.

One of the most fascinating parts of the conference was hearing from large native seed growers who are producing acres of seed on an industrial scale, in places like California’s Central Valley and in the fertile Midwest. According to one presenter, who cited public USDA farm data, there are more than 650 entities growing native seeds in the US. The USDA also lists over 35,000 acres dedicated to the production of native grass seed, and 10,000 acres producing forbs. The native seed farmers on this panel were confident that they could grow out just about any species of seed, if given enough time to understand how to grow it on a large scale. Using tractors, herbicide, armies of seasonal labor, and huge refrigerated storage facilities, they promised “all the seed you can use and more”.

Let’s come back to that after we return to the world of plants for a moment.

2. Smaller is Better

In the opening plenary, Dr. Tom Kaye from the Institute for Applied Ecology shared research showing that biodiversity is essential not just for plant communities, and the web of life that depends on plants, but also for human health and well being. He cited studies showing that the microbiome that coexists with and supports a diverse set of floral life contributes to a more diverse microbiome for humans. This may have positive impacts for everything from immunity and digestion to general mood.

Diversity is crucial because it allows plants – and every other life form – to adapt to changing conditions. On the final morning of the conference, Elizabeth Leger from the University of Nevada presented research from her lab showing that smaller bunchgrasses are better adapted to survive hot, dry conditions, and may even compete better with invasive cheatgrass. While bigger is usually assumed to be better, and certainly has its advantages for plants in many contexts, it was the plants genetically predisposed to smallness that avoided shriveling in the desert sun and held space against a smothering competitor. If the genetics for “smallness” did not exist in these fescues, they might not exist today in the hottest, and most heavily invaded regions of their habitat.

Small has its advantages for trees as well. Another study presented by Erin Baumgart of the US Forest Service showed that Oregon white oak trees subjected to “plant torture” (grown in small pots, pruned to the base after the first year of growth) actually performed just as well or better under drought conditions than trees allowed to reach their maximum size in the same time period.

We would argue that producing plants and seeds on a small scale, in the same bioregions where they adapted and where they will be replanted, makes good ecological sense as well. Though we see a time and a place for large-scale production of seeds at large farms in fertile agricultural region, there are reasons that local food advocates have been calling for de-centralization and de-industrialization of agriculture for fifty years or more. We saw how fragile the supply chain is during the pandemic and extreme weather events of late. And we also believe in the tremendous potential of the native seed economy to transform struggling rural communities, many of which need to transition to non water-intensive crops in the very near future. Small is better.  

3. Climate change is now, let’s adapt

Plants are one of the best defenses against the hazards posed by climate change – they stabilize soils and streambanks, shade the earth, and shelter and provide food for vulnerable life-forms from butterflies to people. Study after study has shown that the impacts of climate change are happening today: Increased frequency and intensity of fires, peak summer temperatures that are hotter and last longer than before, and more erratic weather patterns overall.

We also know that every plant has its “zone” of ideal conditions. They are adapted to thrive in the particular climate, soil type and elevation where they evolved. What we don’t know is how flexible they can be when climate conditions veer into the extremes, especially at the rapid pace at which the climate is changing (an estimated 10x faster than the pace of evolution). Waiting to “see what happens” could mean allowing millions of plant communities to expire before they can adapt.

Many of the NNSC presentations echoed a clear call to action: Assisted migration. Plants need outside help to move into the new climate reality, and who better – with our hands, feet, trucks and seed-drills – than humans to take on the task?

To take on this unprecedented task, there is no agreed-upon set of protocols. But even though the problem is not well studied and models are unreliable, there are some tools that can point us in the right direction.

Tom Kaye highlighted the “Climate-Adapted Seed Selection Tool” which can be useful for identifying species and ecotypes (local, genetically distinct populations of species) to use in restoration and revegetation projects. This tool allows the user to input a broad range of climate variables to obtain an output of where to source seeds that might be “climate adapted”. If unsure which variables to select, Dr. Kaye recommends increasing the winter minimum temperature and lengthening the summer drought period, two factors that have been shown to have an impact on plant germination and long-term success.

In addition, Dr. Kaye advocated for “adapting sourcing”, or choosing seeds from species and ecotypes that fall within a Venn diagram spanning three categories. First, locally adapted seeds. Next, locally adapted seeds that come from populations that have experienced “bad” years (eg. drought) or that eke out a living on harsher sites within the local area. Finally, seeds should be sourced from areas outside the locality that have been identified as climate analog zones. These are areas that models predict will have similar weather to your area in the future. For example some have estimated that the Rogue Basin area may look more like Chico, California in 30 years.

Will adaptive sourcing be enough to preserve plant communities into the future? We heard from another presenter, Jack Zinnen from the University of Illinois, that species diversity is another crucial part of the puzzle. Getting a wider diversity of species into the restoration supply chain is challenging – though plants that are easy to grow and harvest like grasses, trees and showy, generalist forbs are widely available (not as available as lettuce seeds or red maple seedlings, but available in the context of native plants), a large number of genera are not being grown out in farms. These include sedges, anything that is “weedy” (prone to take over agricultural fields) and ugly, late successional plants (which are not often used in restoration projects) and plants with complicated life cycles (which take a long time to produce a marketable product). This is not the fault of farmers (who must pay their bills and feed their families off of these unpredictable and unwieldy plants); those who value ecological diversity are also tasked with making it economically viable.

It’s not a small task; none of this work will be easy. But we returned from the conference emboldened and inspired all the same. We are dealing with tenacious, surprising plants, and creative, hardworking people. We may be small, but we are not alone, and we will adapt.

Another big thanks to IAE for organizing the National Native Seed Conference; we hope to see you there next time.