This study was carried out in the nursery of Ornamental Plants and Landscape Gardening Research Department, Horticulture Research Institute, Agriculture Research Centre, Giza, Egypt in two successive seasons (2015/2016 and 2016/2017) to study the effect of soil drench with some bio- and chemical materials (moringa extract, potassium silicate, salicylic acid and ascorbic acid) combined with different water intervals (1, 2, 3 and 4 weeks) on vegetative growth, flowering and chemical composition of Euphorbia milii var. longifolia transplants grown in 25 cm plastic pots. Results could be briefed in the following: watering at 2 weeks seems to be more effective in increasing the values of most studied characters. On the other hand, both moringa extract and ascorbic acid resulted in the highest values of studied characters. Regarding combination between irrigation intervals and different bio- and chemical materials, all untreated control plants irrespective of their watering regime, in addition to plants watered at 4 weeks interval and treated with either moringa extract or potassium silicate, did not flower at all over the period of this study. Meantime, the same plants recorded the lowest values of many characters irrespective of the watering regime. Plants treated with moringa extract and watered at 1 week interval had the highest values of flower diameter, number of branches, root length and root fresh weight. Those watered at 2 weeks interval achieved the highest rank of number of leaves and flowers, flower diameter, fresh and dry weight of flowers, P%, K% and total chlorophyll content. Plants treated with ascorbic acid combined with irrigation at 2 weeks interval got the highest records of plant height, stem length, leaf length, fresh weight ofleaves, stem fresh and dry weights, total chlorophyll and carotenoids content. In conclusion it is recommended to irrigate Euphorbia milii var. longifolia grown in 25 cm plastic pots at 2 weeks interval, combined with treating plants with either moringa extract or ascorbic acid in order to get the best results.