Known Silverweed Hybrids
Leaky taxonomical abstractions
In this article, I’ll gather together papers that mention successful and unsuccessful crosses of Common Silverweed (Argentina anserina syn. Potentilla anserina) with other species.
There’s a chance you will find this dull, but I for one find the topic of interspecies plant breeding interesting, that of intergeneric plant breeding fascinating, and interfamilial plant breeding astounding.
Just a quick reminder, taxonomists and biologists classify the living world with a series of increasingly specific groups. Skipping the largest groups for simplification, we hit upon families, then a smaller group called genus, a smaller group called species, and what is sometimes called cultivar, variety or subspecies.
Taking the humble store bought apple, it belongs to the Rose (Rosaceae) family, the Malus (Apple) genus, the domestica species, and all your supermarket varieties such as Golden Delicious, Granny Smith, Fuji etc. Plants are generally described by their genus and species (and cultivar) for brevity, so we finally arrive at Malus domestica var. “Golden Delicious”. You can pick this up easily in any British garden centre, any time of year. It’s less of a mouthful than Rosaceae Malus domestica var. “Golden Delicious” (and we’re not even getting into the higher order groups like Order or Clade).
Silverweed also belongs to the Rosaceae family, and regular subscribers might know that it was recently moved from the Potentilla genus to the Argentina genus. And of course, the distinctive species name of anserina. Taken together, you might have Argentina anserina subsp. groenlandica.
Generally, biologists believe that the larger the grouping, the higher the barrier is to creating a cross between plants. So for example, crossing two apple cultivars (like Granny Smith and Braeburn) is trivial and always successful. Crossing two Apple species (like Malus sylvetris and M. baccata) is trickier but pretty common - afterall, interspecific crossing is how M. domestica came about. Crossing two different genus of plants (intergeneric cross) such as Blackberry (anything in the Rubus genus) and Apple (Malus) - both in the Rose family - is meant to be hilariously unlikely. Mention it normal conversation and you’ll probably get laughed at.
As for interfamilial crossing? That’s like crossing apples with oaks, but never say never.
Every so often, I’ll bump into a cool interspecies cross in the ornamental world and I want to scream and shout, “Look, this is amazing! If it can be done here, what other crazy potential is out there?” There’s a fairly large list out there, so people have been trying (but in my opinion not hard enough).
I had this feeling when I learnt about the infamously fast growing Leylandii tree, which is an intergeneric cross between two Cypress trees: Hesperocyparis macrocarpa (Monterey cypress) and Callitropsis nootkatensis (Nootka cypress). The offspring between these two cypress trees is frequently but not always sterile, and different cultivars that you see at your garden centre are actually completely separate recombinations of the two parent genes.
You’ll see that Leylandii is mostly sterile. Mostly sterile, which means there is a route towards creating a stable species if someone wanted the task of growing out thousands of Leylandii cones.
Leylandii is quite well known in the UK for rapid growth. My neighbour planted some half metre cuttings last year and they’re already taller than two metres. This sort of hybrid vigour can cut both ways and Leylandii are known to be shallow rooted and therefore unstable when grown unchecked.
Having said that, crosses don’t always lead to fast growth. I recently planted a beautiful interspecies cross between an English and Japanese Yew (Taxus baccata x T. cuspidata) called T. media. These are some of the smallest Yews, growing very slowly and are tolerant to ornamental shenanigans (pruning). I don’t often plant purely ornamental species but I’ll always make exceptions for cool hybrids.
All this to say, I went ahead and searched online relentlessly of all known Common Silverweed crosses (failures and successes). I did this so you don’t have to. You’re welcome.
PSEUDOGAMY IN THE GENUS POTENTILLA L.
Failure: P. recta x A. anserina
Failure: P. argentea x A. anserina
CYTOGENETIC STUDIES IN THE GENUS POTENTILLA L.
Failure: P. ambigens x A. anserina
Failure: P. atrisanguinea x A. anserina
Failure: P. argentea x A. anserina
Failure: P. recta x A. anserina
Some viewpoints on Fragaria x Potentilla intergeneric hybridization
Success (perhaps): Fragaria vesca x. A. anserina
Failure: Fragaria moschata x A. anserina
Success: Fragaria x ananassa x A. anserina
Biosystematic studies on the species aggregate Potentilla anserina L.
Failure: A. anserina x A. anserinoides
Success: A. anserina x A. egedii
Distant hybridization in strawberry.
Failure (inviable): Fragaria grandiflora x A. anserina
Development and exploitation of interspecific Fragaria and intergeneric Fragaria-Potentilla amphiploids in strawberry breeding.
Failure (sublethal): Fragaria ‘Tioga’ x A. anserina
Summary
The only sure crosses involving Common Silverweed (Argentina anserina) recorded in literature are:
A. anserina x A. egedii (Eged's silverweed)
Fragaria x ananassa (Hybrid Strawberry) x A. anserina
Final Thoughts
A failed cross is just a data point. It means we have not tried hard enough, and if you trawl through the articles you’ll see that this is true. Take P. recta x A. argentina. This cross was attempted twice(!) Just think about that, human couples regularly try more than that to conceive - are we to conclude that humans are not interfertile? There’s so little data it’s statistically insignificant but at least it’s worth recording. If someone had tried a thousand times to failure, I would be more persuaded.
A successful cross is incredible though. The hybrid of Strawberry and Silverweed is a tantalising peek through to the beginning of a new species
It's why I find this sort of plant breeding endlessly fascinating; conjuring exotic and alien species by sloshing two sets of genes together.
It’s a sign that the taxonomy system that humanity has devised is leakier than we expected.
Anyone can do this sort of thing, you don't need much growing space, only an above average level of patience and persistence.
Until next time.
References
PSEUDOGAMY IN THE GENUS POTENTILLA L.
CYTOGENETIC STUDIES IN THE GENUS POTENTILLA L.
Some viewpoints on Fragaria x Potentilla intergeneric hybridization
Distant hybridization in strawberry.
Development and exploitation of interspecific Fragaria and intergeneric Fragaria-Potentilla amphiploids in strawberry breeding
The hybrid strawberry cross is interesting. Supposedly once one hybrid is made, the resulting offspring often have lower fertility barriers to forming hybrids with further species.
Silverweed and strawberry sounds a bit like potato and tomato. One grows a tuber, the other a fruit.