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On the Trail of the Mystery Weed

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(the continued search for the identity of a small, inocuous weed)


Having failed to find my mystery weed at the California site, I went to another weed site, from the University of Illinois. This one works by the process of elimination, even more like using an automated key: in the window on the right is a long list of herbs. In the left window is a series of questions to answer. As you gradually check boxes on the left (leaf type, leaf shape, leaf edge, and so on),  the list on the right shrinks, eliminating the weed names your choice has ruled out. When you have it down to just a few weeds, you can click on them and go see their pictures and a little writeup.

I decided my little white-flowered shepherd’s-purse-like thing was NOT Virginia pepperweed; the edges of the leaves of my plant definitely have no teeth, the way pepperweed does.

Virginia Tech’s weed id site  simply has an alphabetical index, not too helpful if you have no idea what you’re looking for. They do have .pdfs on common weeds and how to deal with them, though.

But I really wanted to get a name for my weed.  I decided to go for the big guns.  The Weed Science Society of America (who knew?)  has pages on Science Policy, jobs related to weeds,  funding and grants, and other areas of weedy interest. They’ve  got a bookstore and a press room.  You can even follow their press releases on Twitter!

Unfortunately, they also use the list method, so you need to have some idea what you’re looking for before you can see a picture or specs. Sometimes this would work for me, but not for this weed .  They do have weed i.d. links, though: one to a DVD you can buy, another to some of their own weed i.d. materials for sale, and the third to the USDA plant database,  one of the most thorough in the nation. Unfortunately, while the USDA plant database will give you a special page on the plants in your state, it uses the list method, so it was a bust on this occasion.

I flicked back to the Weed Science Society page. There was a menu item that had piqued my interest, “The Intriguing World of Weeds”,  where you can find long, multifaceted articles about common weeds, written by Larry Mitich, who was the first weed extension specialist at North Dakota State U.  I intend to come back here, because these are really good articles. And I’ve read a lot of stuff on plants, so I’m not just talking through my hat.

Still, I had to find a name for my plant. I went to another famous ag school, to see what I could see. Rutgers, in New Jersey, gives you a weed gallery, sorted by scientific name, common name, or thumbnail images, so even not knowing the name, I could search there:

My plant does look a good deal like the bittercress there (Cardamine spp.), but the leaves of the bittercress are too big and the wrong shape – and there’s no basal rosette.  The photographs on this site are of noticeably better quality than on other university sites, where overexposure or unclear portraits are common. The ones I checked were by Dr. John Meade, weed scientist emeritus. He does good plant i.d. photos.

The Northeastern Weed Science Society  is a bonanza of weed identification links: the aquatic weed section sends you to about six sites; the terrestrial weed section has about twenty. What makes this much better than Google is that all these sites have been weeded out, so to speak: you know you’re going to good resources, maintained by people who know their stuff.

The weed i.d. sites I’ve already mentioned are on it, plus many more. I went to the one at Penn State,  since that was one I hadn’t tried, but it became clear that their ideas about weed resources were more geared to science: management and ecology of weeds, studies on herbicides. The ecology of weeds (an entire separate site) would interest me at other times, but I kept moving, in hopes of finding my weed.

I went to the U Mass website, but they use the list format. They do add plant families to the list, so that makes it more possible to find a plant that you kind of sort of have an idea about. Still, there are no pictures available until you click a name, which makes for tedious searching.

I couldn’t resist checking out Purdue’s “Common Weeds of No-Till Cropping Systems”, but the page was decommissioned, with a link to their regular Weed Science page. They do have an excellent series of slide shows, sorted by category. I picked  “Simple Perennials”; I didn’t know whether my weed was annual or perennial but it sure has staying power.

I liked that the slides are manually operated, so you don’t have to go “Oh wait, was that it?” as the picture whizzes by. And the slides are good. Text above slides describes what you’re looking at: “Dandelion, mature plant.” “Dandelion taproot.”  I was amused to find multiflora rose as a weed.  The “Annual Broadleaves” slide show was more of a problem; the perennial list, coming in at 33 slides, wasn’t a bad browse, but I wasn’t ready to go through 99 slides of annuals. Still, there is a ton of information to be had on this site. Botanical slide sets, for instance, are listed by family, and there are trustworthy links to other sites.

So how did I finally identify my weed? The old-fashioned way. I went over and asked my gardener/botany fiend neighbor, who’d also done it the old-fashioned way. “It’s some kind of cress,” he said. “I’ve tried to key it out, but I can’t identify the species.”

That was supposed to be the end of the post. But Brent identified this weed as a native bittercress (Cardamine oligosperma) in the last post, providing the species that my neighbor hadn’t yet worked out.  The Latin species name means “few seeds”, which seems odd for a plant my neighbor says spreads itself plentifully (but it’s not hard to remove). If you google “Cardamine oligosperma image” you’ll get some good photos along with some lousy ones (one of the lousy ones, unfortunately, is from the USDA website).

The Calflora site describes the types of areas where Cardamine oligosperma is found, and that’s a fit, too. For those of you who live in California, and have a good guess on the name of the plant in question, this site has a county-by-county map that helps confirm where a particular plant grows.

These last sites have me convinced that Brent has the right i.d.; I’ll see if my neighbor agrees.

So I’ve gotten this weed identified using sort of a combination of the old (ask someone local who gardens or naturalizes a lot) and the new (search online). Check out Brent’s blog  “Breathing Treatment”  for more about native California plants, weather, and gardens.

{ 9 comments… add one }

  • Nickie March 25, 2010, 6:52 pm

    Glad you found it. I just stopped by and bittercress imeadeatly popped into my mind. Great links….I’m going to have to book mark them all and have a good read someday when I’m not too busy!

  • Brent March 26, 2010, 10:37 am

    That’s an epic story! You searched a lot of great places and I’ll have to remember your post as a meta-reference the next time I go looking for a plant ID.

    I was able to make an ID of Cardamine because of some discussion I read on a Yahoo native plants list serve (http://groups.yahoo.com/group/GardeningWithNatives/). It was doubly reinforced because just as I happened to be reading about it I was also experiencing a real life infestation of the stuff.

  • Helen March 26, 2010, 11:55 am

    At a first glance I would have said it was some for of cress as the leaves look very similar to watercress.
    I’m glad you tracked it down

  • Breadnik March 26, 2010, 12:35 pm

    Oh, believe me, here in NE Ohio Rosa multiflora is VERY much an invasive weed, worse than blackberries in CA. When you start pulling it out, it feels like the roots go all the way to Asia, which is where it’s from. And it comes right back at you, just a couple of weeks or months later. Very hard to get rid of.

  • Pomona Belvedere March 26, 2010, 2:01 pm

    Nickie, you have a good eye for weed identification!

    Brent, thanks for the Gardening with Natives group URL, I’ll definitely check it out. My neighbor says he’s not positive about your i.d., because some botanical points haven’t been worked out. Some bittercresses have pointed seedheads and some are flat at the tip, and he hasn’t determined whether that species fits. Ours is flat at the tip. Do you happen to know if that works with C. oligosperma?

    Helen, you’re right, the initial leaves do look very like watercress. Then the plant kind of morphs into something else.

    Breadnik, I know you have personal experience of our blackberries, so I’ll take your word for it about the multifloras. It’s a good reminder to me that a grasping weed in one climate is a treasured plant in another.

  • catmint March 29, 2010, 5:04 pm

    Hi Pomona, I’m impressed by your enthusiastic energetic diligence in hunting out the name of the weed. It’s a pity it’s a weed because it’s actually very pretty. And if it’s a cress does that mean it is edible? I think I have seen it here but it probably isn’t the same one because this one needs lots of damp to survive. Cheers, catmint

  • Pomona Belvedere March 30, 2010, 1:52 pm

    Hello catmint, thanks for using the word “diligence” instead of “obsession”! My neighbor did try this bitter cress and recommended it; the taste is a bit like a cross between arugula and radish. So not something you’d want to eat gobs of, but a very nice addition to a wild salad or to season up a casserole or meat dish.

  • Noel Kingsbury April 4, 2010, 10:59 am

    Ah so that is what it is! I am thankfully free of this pest but it is common in British nurseries, there as an ‘urban myth’ some years ago being spread by folks who should know better that this sp. was introduced by well-known botanist from China. I suppose our one might still be a Chinese sp. It is a bugger, worse that ordinary hairy bitter cress as it is so briftle. Great blog by the way, I will add you to my links on my blog site.

  • Zouhir October 24, 2015, 12:30 pm

    OH MY GOSH!!!Patty, this is absolutely amanizg! Seriously! I only have one foot inside and I am stunned at the beauty of your photographs hanging on these new walls. Way to go, girlfriend! Your hard work has most certainly paid off! (I love this WordPress neighborhood pretty please help me build a house someday here, too!) XOXO

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