PBS Forum

Like many US west coast gardeners, I battle with the weedy Oxalis pes-caprae, known locally as sourgrass for its taste as a salad green (yes, oxalic acid is an antinutrient, don't eat too much). 

I've often wondered about the different ways this plant seems to gear up for summer dormancy. Sometimes it will grow bulblets along the narrow stem coming up from a deeply buried bulb. Other times, the stem will swell and become a storage organ itself. These two strategies will sometimes be found among plants growing right next to each other. 

I'm curious if anyone has insight what might trigger one reaction or the other! 

Photo below shows example of each case. From my garden in Oakland. 

Emil

That succulent root is under the developing bulb. When the plant goes dormant, the root collapses, drawing the bulb down into the soil. Many geophytic Oxalis do this, pulling bulbs inches down into the soil, leaving a void in the soil! So not actually a storage organ, except as a water reservoir at the dry end of the season.

Hello Emil,

Many Oxalis species produce the fleshy root your picture shows. But I do not think that this is a storage organ. The fleshy root only exists on actively growing plants but once they are dormant, no more trace of the fleshy bit. I do not really have an explanation why the plants do that, my guess is that it is a contractile structure which widens the soil around the underground shoot so that the future dormant bulbs can easily descend down the gallery created this way. To me it looks as if the underground shoot has been detached from the fleshy structure.
I had to learn the hard way that pulled up Oxalis pes caprae is quite capable of forming small emergency bulbils from its own substance before it dies. So no longer will it go to the compost place. Before I understood that I contaminated an entire compost with this weed....

Uli

Quote from: Uli on April 02, 2023, 01:59:33 PMI had to learn the hard way that pulled up Oxalis pes caprae is quite capable of forming small emergency bulbils from its own substance before it dies. So no longer will it go to the compost place. Before I understood that I contaminated an entire compost with this weed....

But such a pretty terrible weed! Which the gophers transport everywhere here. Sorry to hear about your emergency tuber infestation...I found that out when I weeded a back yard that was totally covered...I found those emergency tubers at the bottom of the piles of dessicating plants when I didn't get around to putting them in the city compost (industrial hot composting, kills tubers and most seeds).

As I was thinking about the post about invasive bulbs, this one was top on my mind... Is there anywhere someone would want to grow this plant because it's hard to grow there? Or because it's rare there?

Quote from: petershaw on April 05, 2023, 07:06:25 AMAs I was thinking about the post about invasive bulbs, this one was top on my mind... Is there anywhere someone would want to grow this plant because it's hard to grow there? Or because it's rare there?

I don't think it is rare anywhere it can grow easily. My neighbor, who lets me garden her front yard prefers they not be removed since they are so pretty. It makes a pretty pot plant...think abandoned pots in the corner of a yard bursting into bloom winter and spring!

Quote from: Robert_Parks on April 05, 2023, 09:04:25 PM

Quote from: petershaw on April 05, 2023, 07:06:25 AMAs I was thinking about the post about invasive bulbs, this one was top on my mind... Is there anywhere someone would want to grow this plant because it's hard to grow there? Or because it's rare there?

I don't think it is rare anywhere it can grow easily. My neighbor, who lets me garden her front yard prefers they not be removed since they are so pretty. It makes a pretty pot plant...think abandoned pots in the corner of a yard bursting into bloom winter and spring!

I wish I had a neighbor like that! We have a "vacant" house across the street that I could do some planting but every once in a blue moon they send in a string trimmer.

Oxalis pes-caprae

is interesting for exhibiting heterostyly with three morphs, in other words there are three self non-pollinating versions of flowers. A bit like primroses have two (pin and thrum).

I've never knowingly seen this plant here in the North of England. I would like to have photos of the three morphs for the wiki - but maybe they are not that clear.

Quote from: David Pilling on April 06, 2023, 01:59:09 PMOxalis pes-caprae

is interesting for exhibiting heterostyly with three morphs, in other words there are three self non-pollinating versions of flowers. A bit like primroses have two (pin and thrum).

I've never knowingly seen this plant here in the North of England. I would like to have photos of the three morphs for the wiki - but maybe they are not that clear.

Are these three versions visually distinguishable? Is it a heritable trait, ie all clonal descendants will share it? This oxalis doesn't appear to reproduce from seed here in CA, probably due to pollination incompatibility, so I have a feeling that many populations of them here are genetically identical. We might have only one of the three style variants. 

Quote from: plantsperson on April 08, 2023, 05:04:13 PMAre these three versions visually distinguishable?

Presumably, the idea is that the three versions have a physical effect. I only know primroses where the variants stand out a mile, I'd expect them to be passed on to clones.

With primroses you can get seed from pin-pin or thrum-thrum crosses, but they often produce poor plants.

The BSBI (Britain/Ireland survey) says

"A bulbous perennial herb, naturalized as a weed of agriculture, especially in bulb-fields, in milder areas. It does not set seed, but spreads vigorously by easily detached underground bulbils that are resistant to all but the strongest herbicides. Outside the Channel Islands and Isles of Scilly, populations are usually casual. Lowland."

"This species was introduced into cultivation in Britain in 1757. It was recorded from the wild in 1900 (St. Peter's, Guernsey). It remains a prolific but rather attractive weed of bulbfields on the Isles of Scilly."

There's a map, does not show many populations:

https://plantatlas2020.org/atlas/2cd4p9h.60y

Quote from: petershaw on April 05, 2023, 07:06:25 AMAs I was thinking about the post about invasive bulbs, this one was top on my mind... Is there anywhere someone would want to grow this plant because it's hard to grow there? Or because it's rare there?

I have seen it offered for sale in a catalog!

Quote from: Emil on April 16, 2023, 04:48:56 PM

Quote from: petershaw on April 05, 2023, 07:06:25 AMAs I was thinking about the post about invasive bulbs, this one was top on my mind... Is there anywhere someone would want to grow this plant because it's hard to grow there? Or because it's rare there?

I have seen it offered for sale in a catalog!

So far I have resisted the urge to try the (reputedly less invasive) double form. It really is a spectacular bloomer...often with massed blooms fall and spring.