Using Yellow Rattle in PNW Meadows: Good Idea or BAAAAD One?

Yellow Rattle (Rhinanthus minor) is an annual wildflower used widely in Britain to reduce the density of grasses in area being converted to flower meadows. The plant is hemiparasitic on grasses, invading grass roots to pull water and nutrients from them and can apparently reduce grass growth by up to 60% in a season. Over 2 or 3 years of seeding, Yellow Rattle can 'open up' dense grass areas to allow other plants to flourish.

Yellow Rattle can only establish if bare spots are created for it but persistent use of the plant will eventually lead to more bare spots that can be used by it and other self-sowing flowers. A very short seed viability period and fussiness with germinating on undisturbed soil means that this might not be a particularly invasive plant. It is also, apparently, native to our area.

I design perennial meadows on Vancouver Island, working with clients who want low maintenance yards with more biodiversity and color. Many valued flowering meadow plants are aggressive, chosen for ability to compete with grasses. I avoid using plants that could escape over time and become displacers of native plants and, even though Yellow Rattle is considered native, I'm a little concerned about increasing local populations of a plant so effective at reducing grasses.

My question for all of you in the Pacific Northwest is whether or not the Yellow Rattle strategy should be considered for use in our area. It is an effective, chemical-free approach to returning high-maintenance and fertilizer-dependent areas to meadows based on a plant already native here. However, hay farmers may not want to see this plant being used more widely as it definitely can reduce their yields.

Yellow Rattle represents a potentially much lower cost for transitioning lawns to stable meadows. But I am not familiar with the long-term impacts of encouraging this plant.

I'd value input on this. Thanks!

 

I had never heard of Yellow Rattle before and was intrigued to read of its potential to reduce grass growth. You are right to question the long-term strategy of encouraging this plant even though it is native to parts of BC. E-Flora BC Atlas Page

According to E-Flora BC, Rhinanthus minor prefers 'mesic to moist meadows, fields, pastures, roadsides and clearings in the lowland, steppe and montane zones.' In dry areas of Vancouver Island, it would not likely thrive even if seen to be beneficial.

Your description raises so many questions. Some that occur to me are –
· Is it a good idea overall to reduce the density of grasses even if those grass species may be non-native? What is the trade-off? At the times of year when flowers are dormant would the ‘meadows’ then be subject to erosion?
· Where are the areas that may be converted to flower meadows? Are they large tracts of public land or smaller private landscapes?
· Who would decide the location of the meadows in parks and public property and who would monitor their maintenance? How could we ensure they wouldn’t simply open up more habitat for Scotch Broom, blackberries and thistles (among lots of other aggressive weeds)?

Like you, I think many people would be concerned about encouraging increased local populations of a plant so effective at reducing grasses.

Are non-native wildflower meadows worth the risk?

 

Didn't know it was native in BC as well as Europe! Is this certain, or could it be an early introduction from Europe that got to BC before floral surveys were carried out?

If you're sure you can get definite local native sources of it, go for it.

@Margot - could you remove the offensive vernacular epithet you used for Broom, please!

 

Good evening Michael, in Margot's defence, here is the UK wildflower website where the name of the Broom is shown as Scotch. Wiki also names it as such. Now I understand that you and others are offended by the name, but surely organisations such as the attached need to be informed of the insult to stop the innocent misnaming by UBC members.
Broom / Scotch Broom - Wild Flower Finder

 

I am curious about grassfree lawns

And found this decade-old thread started fr Chemainus

A no work lawn

 

https://www.gardeningknowhow.com/plant-problems/weeds/managing-yellow-rattle.htm

Out of self isolated curiosity! ... I typed in the plant name and “invasive” and “killing” and sure enough articles do come up

Like this link - ABOVE

 

I don't want to overreact but PLEASE don't introduce this plant here. Small-scale meadows such as your clients might choose can be kept rid of grasses manually. There are so many hay-fields in this area (east coast of Vancouver Island), it could be a disaster for them to be invaded unnecessarily.
Besides that, as is pointed out in the article @Georgia Strait shared, Yellow Rattle is also parasitic on other plants as well as grasses though to a lesser degree.

 

My sense is also that Yellow Rattle shouldn't be used. Over time it is likely to get from residential areas to hayfields and hurt the yields there.

The British guides to creating yard meadows mention it a lot. But the plant is endemic there and so is not a new threat to farmers. Even though it is native in the Pacific Northwest, it is rarely seen here.

I add ornamental grasses to most of my meadows for background texture and color. This is more of a North American approach that clashes functionally with the Yellow Rattle strategy for helping perennial flowers establish.

Although I doubt I will use Yellow Rattle to speed up lawn to meadow transitions, I think we are going to see increasing residential introductions of this plant here simply because so many meadow creation guides come out of Britain, the seeds are easily obtained, and lawns are being converted to xeriscapes like meadows rapidly.

 

I had heard a theory at one point that the high-altitude populations of Rhinanthus minor were native to BC, while the low-elevation populations were progeny from European introductions. I can put you in touch with the retired scientist who suggested this, if you like. In short, I wouldn't recommend it for your use case.

The overall idea is sound, though -- this is why we are trying to establish a population of Castilleja levisecta in our Garry Oak Meadow and Woodland Garden here at UBC.

 

Seeing your msg Daniel M - I wonder what Nature Conservancy science says for the precious Garry Oak preserve in Cowichan (Duncan BC)

I know thousands of hours of volunteer labor has weeded and continues to weed out the (naming it as we know it commonly here) “scotch broom” and other invasives

 

What's the question about the Cowichan Reserve? I've been several times, I've never seen a population of Rhinanthus on the grounds, nor in their nursery. I do recall they use different management techniques for the upland savannah by the old house vs the former cow pasture near the lake.

 

Oh - I wondered if the NCC had in their initial or ongoing surveys of what the locals call the Elkington Property come across the plant or had considered it to change especially the lower sheep pasture

On a side note - and back to OP - and I am no expert biologist - I would not use what seems like “natural” and then it becomes invasive - that’s my armchair view.