hello all

about 3 months ago I received about 25 tonne of soil from a friend of a friend (long story cut short) to level out my rear garden.

I have moved about half of it so the rest of it is still sitting in my front garden. recently there has a been a explosion of growth of weeds within the pile of soil (in the front garden) an what has started to grow is worrying me

the weeds/ plants are tubular (you can crush the stem between you thumb an finger) and hollow, the stem is green with red flecks like knotweed, the leaves are more pointed than all the other knotweeds i have seen. one thing to note is that on all of the leaves there is a black spot in the centre of all the leaves

most of the plants seem to coming into flower, with red tiny flowers not yet open

i know an id is differcult without a pic i will upload one tonight

does it sound like knotweed?!??

thanks