## 3 Results  
### Plant Heights of the Three Flowering Shrubs at Different Cd Concentrations  
Figure 3 shows that the plant heights of the three flowering shrubs did not substantially change over each month. When the Cd levels in the soil exceeded 200 mg/kg, _H. rosa sinensis_ (Safflower) growth was significantly inhibited and the percentage increases in plant heights were lower than those of the control group, which suggests that Cd had a detrimental effect on plant growth. There was no significant difference in the _Cuphea ipaea_ (Cigar flower) plant growth percentages compared to the control at the different Cd ion concentrations. Cigar flowers had a good tolerance for Cd ions and neither high nor low Cd concentrations affected their growth. _Bougainvillea spectabilis Willd_. (Triangle plum) growth improved in all treatments compared to the control and the plant height growth increase was the greatest among the three shrubs. This result indicated that _B. spectabilis_ had a strong tolerance to Cd ions. Figure 3: _Cont._  
Triangle plum produced the best growth performance in the contaminated soil across the Cd ion concentrations. This suggested that it possessed a high tolerance for Cd ions, making it a promising candidate for phytoremediation or cultivation in Cd-contaminated environments. Cigar flower was the second, and Safflower was affected the worst by the Cd concentration in the soil. The results also showed that low Cd concentrations generally had a promotional effect on plant growth height, whereas high concentrations had an inhibitory effect on growth height. Cadmium Concentrations in the Different Parts of the Three Flowering Shrubs at the Various Cd Concentrations  
[PERSON] defines super-enriched plants as having a cut-off value for Cd of 100 mg/kg and a TF greater than 1 [18]. Figure 4A shows the concentration and TF results for Cd in each part of a Safflower and the Cd concentration in each part of the Safflower as Cd levels in the contaminated soil rose. The plant organ concentration trend was leaves > roots > stems and the TF values were greater than 1, but the Cd concentration in the roots and leaves did not exceed the critical value for Cd super-enriched plants (100 mg/kg). The Cd ions in the Safflower were mainly concentrated in the leaves and the Cd levels were lowest in the stems. The results indicated that the leaves had a certain enrichment effect, but they did not have a high absorption ability. The enrichment effect reaches a critical value at a certain Cd concentration, which can be used to evaluate the Cd absorption and accumulation by plants. This information can then be used to assess the environmental pollution risk due to Cd. The enrichment concentrations and TFs for Cd ions in each part of the Cigar flower (_Cuphea ignea_) (Figure 4B) showed that the Cd concentration in each part of the Cigar flower increased with the soil Cd concentration and the concentration trend was roots > leaves > stems. The TF values were greater than 1 and the Cd concentrations in the roots, stems, and leaves exceeded the critical value for Cd super-enrichment (100 mg/kg) when the soil pollution level was 400 mg/kg. The results indicated that Cigar flowers could be used to bioremediate Cd-contaminated soil when the Cd concentration is 400 mg/kg or above. In addition, Cd enrichment in Cigar flowers was relatively high at concentrations below 400 mg/kg and the Cd ions absorbed by them were mainly concentrated in the roots, indicating that the roots could concentrate Cd ions. Figure 3: Heights of the three flowering shrubs over 1–6 months (**A**–**F**, respectively) at the different Cd concentrations. The Cd contents and TFs for Triangle plum (_Bougaintilla spectabilis_) (Figure 4C) show that Cd uptake increased with soil Cd concentration. The Cd concentrations in the various plant parts also increased with the soil pollution level and the concentration trend was leaves > stems > roots.