by Luke Dahlberg with Citizens for Conservation
This work can be seen at this years GRN workshop.
One of my goals that I wanted to achieve this year was to begin trials on the propagation of hemi-parasitic native plant species. The challenge with these is that they need a sufficient host plant for these plants to grow and develop. While some of the methods I have read about didn’t use a host plant, the overall vigor and development of hemiparasitic seedlings without a host greatly declined in their growth, which mostly lead to mortality of the young plants. With this in mind, I decided to first try one species that I thought would be a good introductory candidate for hemiparasitic plant propagation, and that species was Swamp Betony (Pedicularis lanceolata).
An uncommon species within the region, Swamp Betony is found in a variety of wetlands that include Sedge meadows, fens, wet prairies, and marshes. Like other Pedicularis species, it is a generalist when it comes to hosts, but generally gravitates towards using graminoids and composites. From my experience, Swamp Betony does fairly well from sowing seeds into restorations, and slowly increases in numbers over time. However, the number of plants is still few compared to what you may see in remnant habitats. The flowerheads of Swamp Betony are heavily browsed on by deer, and this makes it a challenge for seed collection in area where deer densities are high. This along with habitat degradation are some of the factors of why Swamp Betony is declining in the region. By propagating plants within a nursery setting, I wanted to see if I could successfully reintroduce Swamp Betony into the wild with plugs, and if there is the potential to plant plugs in protected nursery beds to increase seed production, or directly into the restoration.
Understanding the nature of Pedicularis species, I wanted to use the right host plants for this trial. Swamp Betony can drain a lot of energy from its host, so having a vigorous host in a plug would give enough energy for the developing Swamp Betony seedling. I chose to use Common Lake Sedge (Carex lacustris) and Hairy-leaved Lake Sedge (Carex atherodes) for the trial since they have an aggressive, rhizomatous nature to coup with the Betony. After their needed stratification period, I sowed the sedge seeds roughly a month before the sowing of the betony seeds. This would allow enough time for the sedge seeds to grow and develop into a sizeable seedling so that the betony will have enough root mass to attach to.
When the seeds of the sedges germinated, I transplanted them in small plugs (88 trays). I did this rather than directly into larger plugs with the idea that the root system of the sedge would be more condensed, allowing the seedling of the Swamp Betony to have a greater chance of attachment before being transplanted into a larger plug. Seeds of Pedicularis were sown with a host on April 8th, 2021, approximately 150 days after a cold, moist stratification period. Each plug received one seed to keep track of germination rates and to not overwhelm a sedge plug with more than one Swamp betony plant. First signs of germination began on April 20th, 2021, and continued sporadically for a couple weeks. Once the host sedge was large enough, and the Betony seedlings had a couple pairs of true leaves formed, I transplanted them into larger plugs, where they would continue to grow for the next two months. Growth and development was slow at first, but increased greatly once the summer months hit. In July, volunteers planted the plugs directly into the sedge meadow restoration.
Plugs of both the host and the betony progressed in growth once planted, but the host sedge was less vigorous than regular sedge plugs. Many of the Swamp Betony plants did flower and set seed this first growing season. I’m planning on trying this approach with Wood Betony (Pedicularis canadensis) with upland sedge hosts for the upcoming 2022 growing season.