4 petals and thin straplike leaves. It's a yellow wallflower.

Thank you both for your input! Appreciate it =)

I've only heard of one species in the brassicas family referred to as wallflower.What other plants are referred to by that name? I like using common names quite a bit.Its easier than spelling it out in Latin.Maybe the pic is of a hybrid which no amount of searching will ever identify.

Erysimum is the genus which comprises the plants usually referred to as 'Wallflower' but there are many Erysimum species. To most people I think 'Wallflower ' would imply the brightly coloured spring biennial we see in our gardens. Those are the many cultivars derived from Erysimim cheiri and the pictured plant is not one of them. So in my opinion 'Wallflower' does not give us any specific information about fizgig's plant. If s/he was content with that level of generalisation I don't think s/he would have asked for an id here. I don't see any details which make it definitively an Erysimum at all. The way the petals are separated with visible calyxes and prominent stamens is quite unusual and not something i recognise.

"I like using common names quite a bit. Its easier than spelling it out in Latin." Of course it is fine to use any name you like but if other people are to know exactly which plant is being referred to the botanical name is absolutely essential. Common names are quaint and fun but fraught with problems for accurate identification. If one really wants to get into identifying plants the botanical names are a sine qua non.

Oh,ok,You're right. I wasn't aware erysimum was such a complex genus,but isn't it possible the yellow flowered plant pictured could be a hybrid.Can they hybridized? I really prefer the latin names myself when it comes to making a positive Id. Still curious what other plants are also referred to as wallflower??? There were several species growing in that garden at one time,no? I guess it could be some rare species that's hard to locate on the internet? Now I'm getting interested in learning all I can about Erysimum.

Erysimum capitatum? According to Wikipedia any member of the genus Erysimum can legally have the name WALLFLOWER attached to it.There are,of course a few distinct species of Erysimum and after looking at them I'm offering a yellow flowering Erysimum capitatum as an I'd. Wonder if any people more in the know were around at the public garden where photo was taken. I would have sought them out and asked them.Peace!

Erysimum capitatum is as fair a guess as any in that family... Only thing is that the above were photographed well outside the "western" wildflower's eastern-most range. Being a botanical garden, of course, it's possible for it to be Erysimum capitatum. They have lots of other Wallflower cultivars in all different colors within the garden, but most are named hybrids not the yellows and oranges of the wild Erysimum varieties. I may have to go back to the spot I found these next visit and get better shots of the leaves -- which can be seen most clearly in the shot above directly in the center, right above the central flower cluster and look like mini Chrysanthemum leaves (to me). So the leaves are lobed and not narrow and "grass-like" which I was seeing while trying to ID via the web.... Just about every Erysimum I found photos of had the wrong kind of leaves to fit and/or would not be found in the area -- which I don't put a lot of weight on 'cause of the botanical garden setting, however, I have to consider it because I've never seen these growing wild like this in the garden before.

Plant ID'ing can be so much fun, eh?

Thanks to all who took the time to add their input!! Appreciate it =}

There is very little foliage visible in the photograph but as far as I can see the little there is is deep green, fleshy and deeply divided totally unlike Erysimum capitatum. I am still highly dubious that it is any kind of Erysimum. If anything it seems more reminiscent of a Barbarea. Have you thought of contacting the botanical gardens and asking them about their local weeds?

At floral_uk's suggestion, I checked out various Barbarea species known to be found in the zone and think these little beauties are a match for Barbarea verna. And this is exactly why I posted here =) Just knew someone would come up with a better ID match than my initial field one =)

I worked through the Brassicaceae options in Weakley's keys, and was able to eliminate all genera except Rorippa, Brassica, and Barbarea. It doesn't appear to be Erysimum, because those are all pubescent and your sepals and upper stems are glabrous. I don't think Brassica is an option, because the plant size is too small. Since Weakley says that Barbarea usually flower Mar\-Jun, and yours had lots of unopened buds on June 19, I'm leaning toward Rorippa.

I think you are right, jekeesl. As I said, I thought it was 'reminiscent' of Barbarea but I couldn't match it to any particular species and the flower formation was troubling me. Rorippa sylvestris looks a much better fit with its widely separated petals and very visible sepals.

My only reservation about Rorippa is the habitat --- from what I read, they all like wetland or very moist locations. These weren't growing near any water source (the little stream which used to flow through the spot they were growing in wasn't a natural one so when they stopped feeding it from a man-made pond to do expansion work in the garden, the stream quickly vanished -- in fact all the Yellow Flag Irises which called the stream home died off or at least didn't come up this year). There are also no other Rorippa species anywhere else in the garden.

The bloom time of everything in the zone is off by about a month this year because we had an unusually long, cool Spring this year. We were seeing the earliest of Spring flowers still in bloom 'til the end of May. Even Tulips and Daffodils, which here are done by late March were still around well into May. It's been really weird with the weather this year... LOL =D

Thanks again for the input! Didn't think when I started this thread that it would turn into such a discussion =)

Wow,this is getting deep! I didn't even know about the other brassica species.Happy to see progress being made. I have grown orange Erysimum that came in a wildflower mix and also had another brassica popping up from bird seed the sparrows kicked everywhere.Never was into growing brassicas so I think that's where my lack of knowledge on it stems from.Always have thought the mustards were a bit too weedy for my garden and to me growing biennials like Erysimum is not something I think is worth the patience. I had Hesperis for a long time,but this year got rid of it and planted more natives.Good job,everyone,this has been very enlightening.There were a couple things about the photo that didn't seem to fit Erysimum capitatum,but since I was only looking at the Erysimum species I thought it was the closest match.