The single most likely error is that it has been put too deep in the water. Please refer to the plant descriptions for the ideal depth and if possible err on the shallow side. Other possibilities are: The plant is out of its natural growing season and is still partly dormant. Leaving the plant in the sun or heat in a polythene bag prior to planting – even in less than a minute, plants can cook this way. Damage may not be immediately apparent but they wilt and fail within a few days. There is too much foliage for the roots to support after they have been damaged by the cleaning and packing – I do cut back plants for dispatch but if the weather is hot this still may occur. You can’t do any harm by cutting the leaves back some more – it will help the plant to establish. Too much movement during establishment – if there is a strong current or ducks/amphibians are present then the plant can struggle to establish due to disturbance. Water quality issues – many people worry about chlorine in the tap water, but this rarely affects plants to any degree. If the water is very green and murky, or shaded, then submerged plants like lilies and oxygenators may not receive enough light and can die back. Irises can struggle in high pH and lilies in low pH, but most plants are fairly tolerant of pH 6 to 8.