The weed species composition in a reed canary grass (Phalaris arundinacea L.) plantation for energy purposes depending on its age

The present experiment, carried out in nine production fields of reed canary grass (<em>Phalaris arundinacea</em>) grown for energy purposes, evaluated the effect of plantation age on the occurrence and species composition of weeds. The selected plantations were divided into 3 groups that were conventionally called “young” (1–2 years old), “middle-aged” (3–5 years old), and “older” plantations (6–8 years old). Regardless of plantation age, altogether 43 species were found in the experimental fields. Moreover, 6 species were common for all the plantations and were found in them regardless of plantation age. The least species, only 18, were found on the “young” plantations, almost twice more on the “older” ones (30 species), whereas the largest spectrum of species was found in the “middle-aged” plantations (33 species). In the “young” plantations, annual weeds were the most common, with the highest constancy and coverage index found for <em>Chenopodium album</em>, <em>Matricaria maritima ssp. inodora</em> and <em>Echinochloa crus-galli</em>. The greatest variation in species was found in the “middle-aged” plantations. However, only 4 species achieved the highest constancy and coverage index: <em>Matricaria maritima ssp. inodora</em>, <em>Cirsium arvense, Poa trivialis</em> and <em>Taraxacum officinale</em>. Furthermore, perennial weeds were found to be dominant in the “older” plantations. Within this group, <em>Poa trivialis, Taraxacum officinale, Urtica dioica, Plantago maior</em>, and <em>Cirsium arvense</em> had the highest constancy and coverage index.