Identification: What is it?

I took the pictures at the beginning of June. The two first pictures show the whole length of the plant.

 

I would guess Polygonum douglasii.

 

Thanks Daniel. Yes, it looks like Polygonum douglasii. How this could be though that a wetland species grows here on a very dry land?

 

Hmm... did you look at the ecology information on my link?

From a range of 0 to 8, with 0 being the most dry habitats to 8 being the most wet habitat, it can grow in conditions from 0 to 6, with an average of 2.0. So, tends to prefer quite dry sites.

 

No, I didn't look. I just trusted the information in the INTRODUCTION section just below the top two pictures: "Polygonum douglasii is a native wetland species". In my understanding wetlands are not dry. Evidently the author of the text on E-Flora page didn't see the contradiction.