Plants Aplenty for Pollinators

By Jamie Hinrichs & Cheryl Laughlin
Pacific Southwest Region
June 18, 2024

Native plants and pollinators are forever entwined. Insects, birds and bats transport pollen for plant reproduction, and those plants give back food and habitat. This ecological exchange supports biodiversity in our national forests and for global crops and food security.

Unfortunately, growing wildfires, invasive species, and habitat loss threaten these plants and their pollinators. So, what’s a plant and wildlife lover to do? Enter the restoration and conservation efforts of the USDA Forest Service native plant material program.

Post-Fire Recovery for Pollinators

High-severity wildfires and fire suppression activities may convert healthy habitat into degraded weed-scapes. Fire suppression equipment can inadvertently bring weeds into new areas. And weeds flourish in newly disturbed soils. Without rapid action to remove these weeds, they can be incredibly difficult to eliminate before they wreak havoc on the land.

Early Detection and Rapid Response weed surveys are the most effective way to prevent weed species from taking hold. Within the first few years after a major disturbance like a wildfire, these surveys locate, treat and remove weeds before they can expand.

But while this approach is extremely effective, the sensitive soil is still vulnerable to weed invasion. This is when re-seeding disturbed soils with native plants seeds shines. If native species can take root, they stabilize sensitive soils and help keep weeds out.

Work like this is taking place on the Eldorado National Forest for both the 2021 Caldor Fire and 2022 Mosquito Fire. Forest Service botanists and partners have developed a process of thoughtful seed collection:

• First, find seeds in a similar seed zone — of almost interchangeable habitat conditions — so plant materials can be transferred with a high potential of adapting to a new location.
• Second, include native species that are common and can grow in disturbed conditions like a post-fire landscape.
• Finally, use seeds from native plants that bloom at different times of the year, for consistent food and habitat for pollinators.

“The idea is to create a disturbance/pollinator seed mix where we could put seeds back out in degraded landscapes and re-establish a native seed bank, so native species can flourish and outcompete invasive plants,” said Stephanie Calloway, north zone botanist on the Eldorado National Forest. “We are doing this for all of the seed zones across the Mosquito and the Caldor fire burn scars.”

Seeds for common species will be stored at the Forest Service Placerville Nursery for immediate restoration needs. The Eldorado National Forest and partners at the California Native Plant Society will also collect seeds from five sensitive plant species impacted by both fires. Some of these sensitive plant seeds will be kept at the Placerville Nursery and others will go to the California Botanic Garden, for long-term storage as part of the California Plant Rescue. This statewide effort to store seeds from all of California’s rare plants creates an archive of plant material in case wild populations are lost from environmental threats.

Beyond just seeds, there is also monitoring and research on plant-pollinator relationships to help seed collecting and post-fire restoration. The Eldorado National Forest is capturing this data through an ongoing project on iNaturalist and through new work with a nearby university. 

“We’re conducting a pollinator network study on five sensitive plants that occur in either the Mosquito or the Caldor fire scars,” said Calloway. “A researcher at Cal State University, East Bay and her students will be looking to figure out what pollinates our rare plants and what plants are important to our native pollinators.”

Calloway gives an example of the kind of relationships the study may reveal. If only one pollinator species visits the Stebbins’ phacelia (Phacelia stebbinsii), this means the conservation of that pollinator is essential for the reproduction of that plant. But wait — the phacelia flowers in the middle of June, so it’s also important to know what flowering plants that same pollinator may visit earlier in the year during April-June. These would be the stipulate lotus (Hosakia stipularis), or later in the year, the west coast Canada goldenrod (Solidago elongata).

The Forest Service and partners will target both goldenrod and the lotus for seed collection for use in restoration projects. This gives the pollinator consistent access to flowers for its own survival, so it can also support the phacelia as that plant’s sole pollinator.  

“To be able to protect the plant, we need to know what pollinates it, so we can protect its pollinator. And to protect its pollinator, we need to learn about its habitat requirements.”

How Plant Pollinators and Public Can Work Together

Recreation is also reducing the availability of native plants pollinators require. National forests are lands for both recreation and conservation, but finding the balance takes intention and collaboration. This is especially pronounced in Southern California.

“There's essentially the population of Australia within driving distance of the Southern Californian forests. So, the recreation pressure down here is pretty substantial,” said Drew Farr, restoration botanist on the San Bernardino National Forest. “OHV (off-highway vehicles) can be hard on the land and keeping them on designated routes and out of rare plant habitat can be challenging.”

In addition to healing the land from unintentional recreational damage, grants from the California Off-Highway Motor Vehicle Recreation Division are supporting efforts on the San Bernardino National Forest to enhance pollinator habitat connectivity. This includes invasive weed removal and restoration planting.

“We include species that flower for a long time, what we call ‘workhorse species.’ They're good for pollinators, they grow fairly rapidly, and they help conserve the soil,” said Farr. “Volunteers are the main driver of this work. There are some who remember doing restoration 20 or 30 years ago and now they're sharing that with their kids.”

Volunteers of all ages can cultivate a green thumb through the forest’s nursery facilities. One nursery is part of the National Children’s Forest, offering conservation programs and opportunities for youth to help with restoration. The other two nurseries work to clean, dry, analyze and store seeds from around 150 species. Additionally, onsite greenhouses and seed pollinator beds grow native species, such as native milkweed — the plant Monarch butterflies and several species of native bees need to survive.

“A native milkweed seed group has been working to get some of the native milkweeds that come up early in the season into commercial nurseries, where the public can get them instead of the non-native milkweeds, and we were able to share some of our local seed,” said Farr. “And we heard that folks are starting to see the Crotch’s bumblebee, one of the rare species in California, which is pretty cool.”

Part of addressing the plant-pollinator plight is simply getting it in our sight. Since these species quietly carry out their ecosystem services, the risks they face and their decline from the landscape often fall below our radar. But with efforts like these to support their resurgence, we are invited to bee aware.