It is a simple jump from learning they do not need much water to the idea that you need not be watering an oleander. They like to be watered as much as you would water your shade trees – deeply every three days. To aid in water retention, create a reservoir or dike that is 2-4 inches tall around the trunk of the tree.Click to see full answer. Considering this, how much water do Oleanders need?An oleander shrub needs 1 to 2 inches of water each week while it is actively growing. Let the soil dry out between waterings.Beside above, do Oleanders need deadheading? Shrubs that bloom over longer periods and summer-flowering shrubs, like rose and oleander, respond best to deadheading, but this practice does not extend the flowering time of perennials that bloom over a brief period or of shrubs such as azaleas or hydrangeas, which bloom from a set number of buds. Moreover, are oleanders drought tolerant? Even in the garden, oleander shrubs require minimal care. Although the shrubs are drought-tolerant, they look their best when they are watered during dry spells. However, take care not to over water them. Yellowing leaves indicate that the plant is getting too much water.Why are the leaves on my oleander turning yellow?Improper watering, either too much or too little, may be the cause for yellowing oleander bushes. Although oleanders are highly drought tolerant, they benefit from irrigation during long dry spells. However, too much water can harm the plant and may be to blame for an oleander with yellow leaves.