unusual plant

Does anyone know the name of this large green plant with the tiniest of yellow flowers which has appeared in my garden this year. My garden is full of old flowers and bushes but I have never seen this one before! Thanks

 

it's a Euphorbia, not sure of the exact species though... it's fairly weedy here on Vancouver Island.

 

Looks like Euphorbia lathyris.

 

Thanks! Good to find out that it is poisonous and produces latex!!