Landfill leachate contains high levels of Na⁺, Cl^-, NHx-N, organic matters (including organic contaminants and humic substances) as well as some plant nutrients and potentially toxic elements. Spray or trickle irrigation of untreated or partially treated leachate onto vegetated land can provide a possibility for closing the nutrient cycling loop and simultaneously produce effluent of a suitable quality for discharge, and thus has been considered as a potential remediation option. However, experimental studies available presently have come up with inconsistent results, which are caused by the differences of plant species, leachate components and concentrations, application method, soil properties and climate conditions. Therefore, a pot-based experiment was carried out to investigate the influences of landfill leachate irrigation on the physicochemical and biochemical properties of two dominant soils (a yellow soil and a purple soil), and the growth and uptake of nitrogen, phosphorus and heavy metals by two herbaceous flowers (the Salvia splendens L. and the Dianthus chinensis L.) widely cultivated in southwest China. The concentrations of landfill leachate used were set as 0, 20%, 40%, 60%, 80% and 100%, respectively. The results showed that short-term irrigation with landfill leachate increased the contents of organic matter and nitrogen, electronic conductivity (EC) of the soils, with higher EC in yellow soil than in purple soil, but had no significant effect on the contents of soil phosphorus and heavy metals. The activity of soil urease was suppressed at higher concentrations of landfill leachate, but enhanced at lower concentrations, with the highest activity of urease being observed at the concentrations of 60% and 40% for the purple soil and the yellow soil, respectively. The increase in the concentration of landfill leachate caused a slight increase in the activity of catalase in the purple soil, but resulted in an obvious decrease in the yellow soil. Landfill leachate irrigation inhibited the root growth of two herbaceous flowers, but had dual effects on the growth of their shoots. Landfill leachate irrigation also increased the nitrogen content in the shoots of both plants, but only decreased the phosphorus contents in Dianthus chinensis L. The increase in the concentration of landfill leachate led to an increase of the contents of Pb, Cr and Cd in the shoots of two plants. However, the effects on the contents of Cu and Zn in plants varied with the types of soils and plants. The results from the present study showed that irrigation by landfill leachate with appropriate concentrations could improve soil fertility and thus enhance the shoot growth of plants. Meanwhile, no significant accumulation of excess heavy metals occurred both in soils and plants. It should be noted, however, that the imbalance of nitrogen and phosphorus in soils due to the high nitrogen but low phosphorus concentrations in leachate, and the excessive accumulation of salts in soils at high concentrations of landfill leachate probably impose some potential adverse effects on soils and plants. It is suggested that the optimal concentrations of landfill leachate for irrigation ranged from 20% to 40% and moderate phosphorus fertilizer should be supplemented to keep the balance of nitrogen and phosphorus in soils.