## 3 Results and Discussion
### Phenological Observations
As reported in the literature [32], the competitive ability of _A. millefolium_ is mostly due to its relatively rapid growth. In the _Trifolium pratense_, full germination was completed at 7_DFS, as shown in Figure 2c. The full stem elongation phase (BBCH 3) was completed at 67_DFS, followed by the development of harvestable vegetative parts that reached maximum biomass at 97_DFS (BBCH 49), as shown in Table 4. The reproductive phenological phase was observed after a delay of 2 weeks with respect to yarrow plants, showing inflorescence emergence at 105_DFS and the first open flowers after only 5 days (110_DFS). _Trifolium pratense_ exhibited a constant trend, remaining in phase 4 of vegetative growth and thus prolonging the vegetative phase. In contrast, the species Achillea, despite being exposed to a temperature drop, did not show any slowdown in the progression of developmental stages. It completed its reproductive structures and initiated the flowering phase with the emergence of the first visible flowers. As for _Trifolium pratense_, an intermediate growth period was recorded compared to the other two studied species, lasting approximately 120 days from sowing \begin{table}
\begin{tabular}{c c c} \hline \hline
**DFS** & **BBCH Code** & **Description** \\ \hline
0 & 0 & Germination—Dry seeds \\ \hline
7 & 10 & Leaf development—Cotyledons completely unfolded \\
21 & 12 & Leaf development—2 true leaves \\
34 & 18 & Leaf development—8 or more true leaves \\ \hline
42 & 32 & Steam elongation—Stem 20\% of final length \\ \hline
67 & 47 & Harvestable vegetative plant parts have reached 70\% of final size \\
76 & 49 & Harvestable vegetative plant parts have reached final size \\ \hline
90 & 59 & Inflorescence emergence—First flower petals visible \\ \hline
97 & 60 & Flowering—First flowers open \\
105 & 61 & Flowering—10\% of flowers open \\
110 & 62 & Flowering—20\% of flowers open \\
116 & 64 & Flowering—40\% of flowers open \\ \hline \hline \end{tabular}
\end{table} 
Table 3: BBCH phenological scale of _Achillea millefolium_ with days following sowing (DFS). to flowering and consistent with other studies on Trifolium [33], although this period is influenced by climatic conditions, which vary by year, climatic region, and sowing season. The growth followed different patterns as each species reached its phenological stages at different times. In Figure 3, all the phenological trends of the three species studied can be observed. We observed that the two species belonging to the Asteraceae family (i.e., yarrow and milk thistle) exhibited similar behavior during the first two stages of their phenological development: Stage 0 (germination), which lasted for 7 days, and Stage 1 (leaf development), which lasted for 35 days for both species. A temperature accumulation of 848 GDD was required to complete phenological stage 1 for both Asteraceae species, whereas a lower accumulation of 573 GDD was sufficient for _Trifolium pratense_. For phenological stage 3, _Achillea millefolium_ exhibited the lowest temperature accumulation, requiring 464 GDD, whereas _Trifolium pratense_ necessitated a considerably higher GDD amount (1000 units), a very similar condition to that of _Silbyum marianum_, where 1115 GDD were required. However, _Trifolium pratense_ reached the stem elongation phenological stage (BBCH 3) earlier than the two Asteraceae species (characterized by composite flowers) and maintained this stage for 42 days. However, the _Silbyum marianum_ reached the rosette phenological stage (BBCH 3) at a later time, around day 42, and maintained this stage for a longer duration than the two other species, lasting 48 days as shown in Figure 3. During the phenological stage (BBCH 4), to complete the development of harvestable vegetative biomass, _Silbyum marianum_ required only a temperature accumulation of 325 GDD, while _Achillea millefolium_ and _Trifolium pratense_ necessitated higher accumulations amounting to 525 and 680 GDD, respectively.