Polygonum cuspidatum

Polygonum cuspidatum bush

Knotweeds, also known as polygonums (or polygoni?) belong to knotweed family (Polygonaceae), a characterristic feature of this family being that lots of plant have swollen  or at least dictinct joints. That is well reflected in the Latin name of the family: poly means "many" and goni means "knee" or "joint". As a typical representative of the family, polygonum is a classic example.

There are a whole lots of polygonum species. Some grow in or near the water and some on high ground. I found one specie growing on high ground right here in the town where I live. An interesting thing is that it seems to grow at just one particular location as I've never seen it anywhere else. It is probably Polygonum cuspidatum but the species are hard to tell apart.

And here is a close-up of the branch where you can see these swollen joints.

Polygonum cuspidatum joint

The stems are red or reddish. The leaves are big, nicely shaped and symmetrical.

Polygonum cuspidatum branch

The flowers are small, formed in spikes. In this particular species the flowers are white but some species have pink flowers. They are shaped the same though.

Polygonum cuspidatum branch

And here is a nice picture of close-up of the flowers Notice the black anthers.

Polygonum cuspidatum flowers

And while we are at it I have another picture of different polygonum species.