Abstract
Lamium amplexicaule L. (Family: Lamiaceae) is a cosmopolitan weed whose eradication is challenging. The phenoplasticity of this species is related to its heteroblastic inflorescence, which has not received adequate research worldwide in its morphological and genetic aspects. This inflorescence hosts two flower types, a cleistogamous (CL: closed flower) and a chasmogamous (CH: opened flower). This species subjected to detailed investigation is a model species to clarify: (1) the existence of the CL and CH flowers in relation to the time and individual plants. (2) the predominant flower morphs in Egypt. (3) the morphological and genetic variability between these morphs. Among the novel data retrieved from this work is the Presence of this species in three distinct morphs coexisting during winter. These morphs showed remarkable phenoplasticity, particularly in flower organs. Significant differences were observed between the three morphs in pollen fertility, nutlets productivity and sculpture, flowering time, and seed viability. These differences were extended to the genetic profile of these three morphs assessed by the inter simple sequence repeats (ISSRs) and start codon targeted (SCoT). This work highlights the urgent need to study the heteroblastic inflorescence of crop weeds to facilitate its eradication.