Phytoextraction is a technique which uses plants to clean up metal-contaminated soils. Recently, various chelating agents were introduced into this technique to increase the bioavailability of metals in soils. Even though the technique is an economic and environment-friendly method, this cannot be applied in highly metal-contaminated areas because plants will not normally grow in such conditions. Therefore, this research focuses on identifying chelating agents which are biodegradable and applicable to highly metal-contaminated areas. Alunimum (Al) as a target metal and cysteine (Cys), histidine (His), citrate, malate, oxalate, succinate, and ethylenediamine (EDA) as biodegradable chelating agents were selected. Ethylenediamine tetraacetic acid (EDTA) was used as a comparative standard. Plants were grown on agar media containing various chelating agents with Al to analyze the effect on plant growth. His slightly diminished the inhibitory effect of Al on root growth of plants, whereas, Cys, citrate, malate, oxalate, and succinate did not show significant effects. Both EDTA and EDA strongly diminished the inhibitory effect of Al on root growth. The effect of EDA is correlated with decreased Al uptake into the plants. In conclusion, as a biodegradable chelating agent, EDA is a good candidate for highly Al-contaminated areas.