Propagation of Wood Betony (Pedicularis canadensis)

By Luke Dahlberg, Citizens for Conservation

I have heard from many in the restoration community over a several year period that there has been a “Pedicularis” interest in this plant, and I “wood bet’ony” that any information to continue to restore this species would be helpful (Unlike my cheap plant puns…)

In my continuing journey to understand the growth and development of our native plant species, I wanted to focus on propagating hemi-parasitic plants. This group of plants will attach to and take nutrients from neighboring plant hosts, but they can photosynthesize and take up water and nutrients on their own. I started this process last year with Swamp Betony (Pedicularis lanceolata), and had great results with that initial germination trial. This year, I wanted to step up to the next challenge to try growing from seed it’s close relative, Wood Betony (Pedicularis canadensis)

Found throughout much of the eastern United States and Canada, Wood Betony can be seen growing in prairies, savannas, and open woodlands. Much like Swamp Betony, it is a generalist when it comes to host plant preferences, but it does tend to favor aggressive warm-season grasses such as Big Bluestem (Andropogon gerardii), and Indian Grass (Sorghastrum nutans), and composites such as Goldenrods (Solidago sp.) and Sunflowers (Helianthus sp.).

At Citizens for Conservation and other Barrington Greenways Initiative preserves, Wood Betony is doing quite well in these restorations due to continuous collection and seeding of this species, and frequent burns that may be stimulating seed germination and growth. However, colonies of Wood Betony are still localized and not spreading as much as I thought it would. Their dispersal mechanism doesn’t spread them far and wide, but the plants are stoloniferous. Literature that I’ve read also tends to say that it’s “Difficult from Seed,” meaning that it’s either slow to grow from seed, or it has little to no germination. Like most early-flowering plants, Wood Betony starts going to seed early, usually around Memorial Day week in the area.

Growing research and my personal germination trials have shown that many of these species that go to seed early tend to have increased germination rates where their seed is sown from a week to a month after collecting the seed. If dried for too long, many of these species lose viability quickly or go into a prolonged dormancy where they make take at least two years to germinate. I wanted to know if Wood Betony was in this category. In general, there were several reasons why I wanted this germination trial:

  • Being partially parasitic, I wanted to know if Wood Betony needs a host plant for germination or not.
  • To see If germination increases the following spring by sowing the seed during the summer months or not.
  • If Wood Betony plugs are successfully propagated, they can be planted in dense areas of Big Bluestem (Andropogon gerardii), Indian Grass (Sorghastrum nutans), Canada Goldenrod (Solidago canadensis), Sawtooth Sunflower (Helianthus grosseserratus), Tall Goldenrod (Solidago altissima), and Woodland Sunflower (Helianthus strumosus) where seeding Wood Betony has not worked
  • To find out why it is “Difficult from Seed”

I began the process when I collected seed in June of 2021. One batch of seed went into a treatment of warm, cold, warm stratification in July, about a month after collection. Stratification is basically conditioning of the seed, and this breaks down dormancy mechanisms in the seed so the embryo knows when to germinate. The vast majority of native plants achieve this during the winter months. The second batch I kept dried out and gave them only cold stratification starting in November. For the host species, I chose two species of sedges and a grass. They were Copper-shouldered Oval Sedge (Carex bicknellii), Hairy Wood Sedge (Carex hirtifolia), and Slender Wheat Grass (Roegneria trachycaula).

Similar to how I propagate Swamp Betony from seed, I sowed the seeds of the host species about a month ahead of the betony sowing. This will give the host seedlings time to grow and develop before they have a betony seedling growing along with them. I sowed the Wood Betony in the beginning of April with the sedge and grass seedling in their individual plugs. Germination for the Wood Betony occurred in roughly two weeks from sowing the seed. The seed that was given a warm, cold, warm stratification cycle has nearly 100% germination of the seeds, while the seeds that were only given a cold period did not germinate. Even after a couple of months waiting, that second batch still did not germinate. Did they go into a longer period of dormancy, or lose viability?

I had similar results with the seedlings that did not have a host. Though I had a lot of initial germination, many of the seedlings did not make it to developing leaves. I wasn’t sure if this is normal for Wood Betony, or if it was grower error (usually, it’s the latter). As the growing season continued, the young plants continued to develop, and by the end of July were at a size to plant into the ground. Of the three hosts plants I had, the healthiest and biggest Wood Betony plants had Carex bicknellii as their host species. I plan to overwinter the plants in the plugs and plant them out in the spring either in seedbeds or into areas of dense colonies of Goldenrods and Sunflowers.

From the results I had with this experiment, the seeds of Wood Betony greatly benefit from sowing the seed about a month after collection, similar to the time frame that the plant disperses its seeds. At one of our Citizens For Conservation sites known as Flint Creek South, we sowed Wood Betony seed into a younger savanna restoration, and I’ve seen multiple Wood Betony plants the year after from this early sowing. However other factors may have been in play for good germination such as frequent burning, little competition, and soil conditions that favored the plant. For the backyard gardener, hobby grower, or experienced propagator, growing Wood Betony with the same or similar method will help this bring this important plant into our restorations.

Wood Betony (Pedicularis canadensis) seedlings with Copper-shouldered Oval Sedge (Carex bicknellii) host on 4/18/2022

Wood Betony seedlings sown in a tray without a host. This is from the warm, cold, warm stratification method. The cold stratification batch had no germination. Photo taken 5/02/2022

Wood Betony plants with sedge host on 5/09/2022, about a month after sowing the seed in the greenhouse.

Volunteers helping pot up seedlings. We cannot have the plant plugs that we have without the dedicated time and work from our great volunteers!

Wood Betony plug with sedge host on 6/08/2022

Wood Betony plug with sedge host on 7/22/2022. This plug is large enough to be planted.

About Grassland Restoration Network blog

Bill Kleiman publishes this blog. Bill's daytime job is manager of Nachusa Grasslands. We are looking for guest authors on various topics of grassland habitat restoration. Contact me with your ideas or drafts.
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16 Responses to Propagation of Wood Betony (Pedicularis canadensis)

  1. prairiebotanist says:

    I appreciate the puns! Anecdotally, myself and others have had great success sowing fresh seed (so it would get a warm, moist period) into both Pennsylvania sedge, with other prairie species into brome CRP land, and into established warm season grasses where thatch has been removed by prior burning, and where sites also receive annual dormant season burning subsequently during the establishment phase. So the need for warm, moist treatment (or loss of viability if subject to that) is consistent with those anecdotes. While clonal, individual plants seem to be short-lived (create small clones that subsequently die out) and outcrossing, so long-term establishment *might* depend on getting a critical number genetic individuals close enough to one-another to cross-pollinate. So if seed amounts are limiting, it may be better to aggregate seeding (or planting) in scattered foci from which plants may spread. …another research question there to go on the stack.

  2. Henry Eilers says:

    Great project. That needs to be scaled up to a another level.
    Similar work is needed for other difficult species. G puberula and L canescens come to mind

  3. johnayres43gmailcom says:

    Thank you as this is great information as I was going to add to my seed mix and disperse in December. Putting out now instead. May be too late already?

  4. prairiebotanist says:

    Talk to Dustin Demmer of Blazing Star Gardens. He is producing both Gentiana puberulenta and Lithospermum canescens commercially. I’m told Lithospermum actually isn’t hard, but the nutlets that plants retain are the bad ones. The good ones fall to the ground earlier.

    • Luke Dahlberg says:

      Dustin has been on my radar of people to reach out to for more growing experience. I’ve grown both Lithospermum canescens and Gentiana puberulenta with great results. L. canescens is a recalitracnt, so it has to be sown freah, along with G. puberulenta. the latter I’ve had issues with seedling mortality, so I’ll have to see what Dustin is doing for a growing medium or any other specieal treatment to keep them alive.

  5. Pam Richards says:

    Thank you for this education. I winter sowed many native species last winter into plug trays. Most did pretty well except the wood betony and prairie bush clover. Next time I will try to plant with a grass as you had this success. I did get a couple wood betony and now ( September) I see many seedlings in WB tray but may be weed-blown-in seedlings. Not sure.
    Actually a question: you mentioned you left your plugs out all winter. Is that in a greenhouse then? I have many plugs of natives left which I am giving away but wonder how they could overwinter again (freeze up plugs). I planned to plant them into ground but would rather save them
    For next spring. But didn’t think they could take the freezes. Northwest illinois.
    Thank you.
    Pam Richards

    • Luke Dahlberg says:

      Great question! I overwinter my plugs in an unheated structure such as a barn or unheated hoophouse with white plastic over it, or outside in the elements with frost blanket covering the trays. They plugs can freeze solid to survive the winter, but constanct freezing and thawing will kill the roots. as long as they’re in a spot where there is not extreme temperature changes, and protected from winter winds, they’ll be good to survive the winter.

      • Pam Richards says:

        Thank you so much. I did plant so many in ground past two weeks as the poor things were nothing but roots being outside since December. I may transplant some next year but will remember this for future.
        On a side note our couple of wood betony plants have really grown a lot just in past month ( compared to all summer) for whatever reason.

  6. Outstanding work, Luke. On a side note, you have probably noted that P. canadensis seedlings exhibit one of three color morphs early in the season (red, bright green, and an intermediate) that become difficult to discern as the season progresses. Your photos show the green morph. On our site in McLean County, IL we have all three morphs. These color morphs suggest a single gene controlling anthocyanin production as a cool-season sunscreen, in which case the red should be more common where spring days are cool and bright. It would be interesting to know the distribution of color morphs across its range as well as within populations.
    Thanks for sharing your work.

    • Luke Dahlberg says:

      That is very interesting information! I know our wild populations have the red leaves in the early season due to the cool temperatures, and these seedlings were in a 70 degree greenhouse when growing, hence the green foliage. Do your populations also have red flowers or just the typical yellow flowers?

  7. Laurel says:

    What is your protocol for germinating Carex seeds? I’ve been told that most sedges have very low germination and that has been my limited experience with seed purchased from vendors. It was also suggested that the seed should be sown very soon after harvest.

    • Luke Dahlberg says:

      Carex are a very diverse group of plants, and because of that diveristy, germination requirements are across the board. In my experience, I’ve grown many different species of Carex with successful results, and here’s a couple things I’ve learned. The early-blooming sedges such as Carex pensylvanica and Carex meadii need to be sown quickly since they lose viability as the dry out. Other sedges such as Carex bicknellii and Carex muskingumensis can wait until the fall to be sown. Many of the robust wetland sedges such as Carex lacustris and Carex pellita are self-incompatible, so while they may produce a large colony, flower, and form fruit with seeds, the seeds may not be viable. To play it safe, as you mentioned, sow the seeds of sedges soon after harvesting them, and you should have good germination results.

  8. Carol Buelow says:

    I found this really interesting, and I want to try the warm-cold-warm stratification. Could you spell out the time periods and temp ranges? Also, do the host plants need to be new seedlings, or could they be small but mature plants? Or would that be too much competition for the betony. Thanks!

    • Luke Dahlberg says:

      Those are great questions! The warm-cold-warm cycle is pretty simple. Once the seed is collected and cleaned, you can start the warm stratification process. Mix the seed with damp sand or vermiculite and place in a ziploc back at room temperature (70 degrees Fahrenheit) for at least 90 days. After that, place the seeds in cold stratification (40 degrees Fahrenheit) for a minimum of 90 days either in the refrigerator or outside in a rubbmaid bin or closed bucket, and keep in an unheated shed or garage. Once they are done with cold stratification and placed in the second warm stratification period, the Wood Betony seeds should germinate. You can also sow the seeds in a tray after they are cleaned and let the natural temperature cycles take their course. For the host plant size, you can use mature plants instead of seedlings, as long as there’s enough space for the Wood Betony seeds to germinate and grow.

  9. Asil E says:

    Hi, Can you provide your protocol for warm-cold-warm treatment of the seeds?
    Thank you!

    • Luke Dahlberg says:

      What I did for the warm-cold-warm cycle was place the seeds in warm stratification for 90 days followed by cold stratification for a minimum of 90 day, and they will germinate during that second warm period. You can accomplish this by placing the clean seeds in damp sand or vermiculite in a ziploc bag, and leave it at room temperature (70 degrees Fahrenheit) for 90-120 days. After that, place the seeds in cold stratification (40 degrees Fahrenheit) for 90-120 days. This can be accomplished by placing the bag in the refrigerator for that time, or outside in a Rubbermaid bin or closed bucket and leave in an unheated shed, garage, or other protected location. The seeds will germinate after the second warm cycle once the seeds are sown. You can also sow the fresh cleaned seed in a tray with potting mix and leave outside to allow them to go through the natural temperature fluctuations.

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