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Silybum marianum (L.) Gaertn. (milk thistle) is plant species that has been utilized principally for medicinal purposes for more than 2000 years. Recently it was proposed for biomass production in marginal environments, but vegetative biomass compositional analyses had not been available so far. The study of plant morphology and biomass composition was conducted on three different S. marianum accessions grown under open field conditions. The results indicate that plant morphological traits show major differences between accessions: this suggests that the available natural variability can be further utilized in order to develop improved S. marianum cultivars. Biomass compositional analysis shows that extractives, ash, lignin and cellulose content are comparable to other herbaceous bioenergy crops and that these traits display only limited variability in the studied accessions. Hemicellulose fraction is composed only by xylans and its content appears averagely lower in comparison to other herbaceous biomasses. Interestingly, in S. marianum biomass total nitrogen content is lower if compared to other herbaceous species. The possible involvement of this specific biomass trait in S. marianum nitrogen utilization efficiency has to be further investigated.

Silybum marianum (milk thistle) is among the top selling herbal products in the U.S., in Italy and in other countries. Despite its economic importance as an officinal and medicinal species, only few improved genotypes exist and the species is still marked by traits that are typical of non-domesticated plants. Based on this evidence, further genetic improvement is required for the complete exploitation of milk thistle as a crop species. The first step in order to allow further breeding programmes of the species is the setup of a reliable crossing protocol. The present paper, after a brief review of S. marianum flower anatomy, describes a crossing method for this plant. The correct phenological stage for emasculation is BBCH growth stage 54. If manual pollination is repeated two days after emasculation, a significant increase of F1 fruits can be obtained. By utilizing the proposed protocol, an average 70–90 florets per flower head are emasculated and percentage of success (F1 fruits harvested) usually ranges between 27 and 70%. The proposed crossing protocol will constitute an important tool in order to allow the further genetic improvement of this species.

In moderate climates where milk thistle is grown as a medicinal plant it emerges slowly and unevenly and thus it is exposed to weed infestation. The aim of this study was to estimate if the storage temperature and thousand seed weight (TSW) of the seed material have an effect on the number of emerging plants. In the 3-year field experiment, seed material that had been stored at 23, 15 and 7°C and separated according to TSW: 26–30, 20–22 and 20–30 g (control) was used. The emergence of plants was evaluated 4 times, from the BBCH growth stage 09–12 to 18–19/37–38. Storage of seed material at 23 and 7°C resulted in an increase in the number of emerging plants in comparison with seed material stored at 15°C. These differences were evident only at the first time of measurements and gradually reduced as growth progressed. A significantly higher number of plants per 1 m2 was obtained from seed material with TSW 26–30 g as compared with the seed material with TSW 20–22 g. These differences continued at all measurement dates but only in one dry year they did have a positive effect on the achene yield.