Hi Neil: With regards to Lythrum salicaria. Our problem invasive has been shown to actually be a hybrid swarm between L. salicaria and our native Lythrum - which perhaps explains why it has become such a problem. Boyce Tankersley Director of Living Plant Documentation Chicago Botanic Garden 1000 Lake Cook Road Glencoe, IL 60022 tel: 847-835-6841 fax: 847-835-1635 email: email@example.com -----Original Message----- Boyce: Purple loosestrife (Lythrum salicaria) is a fairly common plant here, but well liked and not at all a nuissance. Even more ironic is Water chestnut (Trapa natens) which is a nuissance in the Hudson river, yet an almost mythical and sadly extinct plant here. It is said to be the only plant made extinct by botanists, last one was seen here in 1913, it is suspected that the hobby of herbarium collections in the 18th century finshed them off!