## 3 Results and Discussion
### Phenological Observations  
The seeds of the study plants were sown on 20 June 2024 in multi-pots and maintained under controlled temperature conditions. After germination, the shoots were transplanted into larger pots and placed outdoors for about 12 weeks under natural environmental conditions. In _Silybum marianum_, the beginning of leaf development, corresponding to BBCH 12 in Figure 2a, occurred just seven days following sowing (DFS). After the emergence of the first pair of true leaves, leaf development progressed with an increase in leaf number until a rosette stage was established at ground level (BBCH 31), which took place at 42_DFS, as shown in Table 2. By the 90 th day following sowing, vegetative growth resumed as the plant transitioned into stage BBCH 4, marking the onset of vegetative biomass development. This process continued until reaching the phenological stage 49 by the 105_DFS, where peak biomass accumulation was observed. Figure 1: Trend of mean temperature and GDD amounts during the plant developmental season. Figure 2: _Cont._ \begin{table}
\begin{tabular}{c c c} \hline \hline
**DFS** & **BBCH Code** & **Description** \\ \hline
0 & 0 & Germination—Dry seeds \\ \hline
7 & 12 & Leaf development—First pair of elliptic true leaves visible \\
21 & 15 & Leaf development—Five leaves visible \\
34 & 18 & Leaf development—Eight leaves visible \\ \hline
42 & 31 & Rosette growth—10\% of ground covered by leaves \\
67 & 37 & Rosette growth—70\% of ground covered by leaves \\
76 & 39 & Rosette growth—90\% of ground covered by leaves \\ \hline
90 & 42 & 20\% of the maximum biomass reached \\
97 & 47 & 70\% of the maximum biomass reached \\
105 & 49 & 90\% of the maximum biomass reached \\ \hline
110 & 50 & Flower central head present (3–5 mm \(\diameter\)) but completely \\  & & enclosed between developing leaves \\
116 & 51 & Flower central head clearly visible between leaves, vertical \\ \hline \end{tabular}
\end{table} 
Table 2: BBCH phenological scale of _Silybum marianum_ with days following sowing (DFS). Figure 2: Selected species’ main phenological phases with BBCH codes: (**a**) _Silybum marianum_; (**b**) _Achillea millefolium_; (**c**) _Trifolium pretense_. As regards _Sillybum marianum_, we recorded a growth cycle duration of 100-130 days, which is consistent with findings from other similar studies [29; 30] where under severe winter conditions, the species can be defined as an annual summer crop [31]. The phenological analysis of the selected species showed significant differences in their vegetative development. After a first growth phase similar to the other species, the _Sillybum marianum_ reached the rosette phenological stage (BBCH 3) at a later time and maintained this stage for a longer duration than the other species. This extended period was because, differently from the other two perennial species, _Sillybum marianum_ follows a biennial cycle, with buds located at ground level. Moreover, the response to temperature trends during the cultivation period showed different effects on the selected species. _Sillybum marianum_ transitioned from phase 3 to phase 4 at the onset of significant cooling recorded during September, shifting from horizontal vegetative growth (rosette) to vertical growth by developing the bud. In the _Achillea millefolium_, the cotyledons unfolding (BBCH 10) was observed after 7_DFS, as shown in Figure 2b. The vegetative phenological development was similar to the other species of the same family (milk thistle) with the complete leaf development reached at 34_DFS and the stem elongation (BBCH 3) at 42_DFS, as shown in Table 3. The harvestable vegetative plant reached its final size at 76 DFS (BBCH 49). The reproductive phenological stage started at 90_DFS with inflorescence emergence while in the successive 4 weeks, the flowering process advanced to about 50% of flowers open. Generally, the _Achillea millefolium_ takes less than 100 days from seed germination to flowering, although this can vary based on environmental conditions and care practices.