Still a mystery. Looks like its name should have "cress" in it.

I think this is the same plant that I noticed last spring. Right here.
[4/19/10: Hairy bittercress (Cardamine hirsuta)]

??? It's kind of viney.

Yarrow? Yes, says Michelle. Achillea millefolium.

Could be lady's thumb, or Pennsylvania smartweed, or tufted knotweed. Anyone know for sure?

???

4/12/11: Turkish speedwell (thanks andrea, see comments). A delicate and hardy little groundcover.

Veronica liwanenis

See also September 23. Looks like, but isn't, rosemary. Even has the same tiny flowers. Has great fall color. [8-13: might be bog-rosemary per Andrea]

Jerusalem artichoke?

Most people, including me, wouldn't call these weeds. But they come up every year in the park next door and I've never been sure what they are. Deer don't eat them so I'd like to borrow a few plants for my yard in the hope they'll spread.

???

Spotted in my friend Shannon's front yard.

Yes, nutsedge. Specifically yellow nutsedge.

Cyperus esculentus.

It looks like wild rosemary but is there such a plant? [8-13: Andrea says Andromeda polifolia or bog-rosemary so we're going with that for now.]

??? Shepherd's purse maybe?

??? (10/6: could this be nutsedge???)

12/26/09 update: Aporn says this is an obedient plant.

Physostegia virginiana.

Sowthistle (Sonchus arvensis). [5/24/10 update]

???

???? Boneset maybe?

And this is ...?? (9/18: Possibly white wood aster.)

Eurybia divaricata.
This is what I'm calling it until someone corrects me.

Now that this weed has finally bloomed I should be able to identify it. (Clammy Ground Cherry, 9/23.)

Physalis heterophylla. (Yes, Michelle, it is a nightshade.)

What IS this stuff? St. John's Wort, I do believe.

Hypericum perforatum.

???

Spotted spurge (Euphorbia maculata).

Some call this a weed. I call it salad. Purslane.

Portulaca oleracea.

A big climbing weed called, some say, Trumpet Vine. It likes to climb up the downspout and onto the roof. But it's never bloomed...

Campsis radicans is the Latin name for trumpet vine. I'm not totally sure that this is the correct ID. More research is called for.

This stuff is everywhere. It's called dock, says gaiagardener. Rumex obtusifolius.

Is this what everyone calls crabgrass? I'm guessing that Lori KP (see comments) is right: it's goosegrass (Eleusine indica).

This plant is close to 4 ft tall. No sign of a flower. I so want to hack it down. But I want to see if it blooms. (7/8: Dug it up. I'll never know.)

(9/26/09 update: Eastern redbud seedling)

I still have no idea what this is. It's not a tomato. Looks like a gigantic marigold without the flowers.

A tender grass. Seems to like water.

I think most people would call honeysuckle a weed. I really need to think about pruning this thing.

?? Between the driveway and the carport. Now THIS is a hardy weed.

I really, really want to stop buying books, but how can I resist this?

Found all throughout my vegetable garden. What is it? It's not dandelion. (9/23: Dock for sure.)

Pokeweed! It might be the most common weed in my yard. Mostly in my flower beds.

Tickseed or coreopsis.

Money tree or money plant (Lunaria annua). They get nice translucent silver discs in the fall).

Also called honesty plant. I saw these purple wildflowers on the side of a road in April, not on someone's property but on city property. They looked like some kind of tall roadside weed, so I didn't think it was so wrong to pick just two flowers. I stuck them in dirt and they are now quite happy. Ugly but happy. I'll plant them in my wildflower garden, near the back. I read that they are one of those dreaded and dreadful biennials. Bloom twice and then die. I've come to dislike the whole idea of biennials. Seems unnatural. Plants should bloom always or once. Not some wishy washy middle ground. The top photo is from www.zum.de/stueber/lindman/212.jpg.

I've got 18 books on weeds and wildflowers and vines and grasses. And yet there are still some weeds that I can't find.

Books for my weed-identification project.

Johnson grass?