Annuals and perennial plants generally have a higher demand for water than woody ornamentals. However, wait for them to wilt before watering. If a total ban on outdoor watering is imposed and you cannot water anything, the best advice is to cut back annual and perennial flowers that wilt in an effort to reduce their moisture loss and make certain they are well mulched. Avoid shallow watering. The worst thing you can do is to water them frequently and shallowly.
Less water is lost to evaporation when watering in the evening or at night.
Watering during this time will not encourage disease since the foliage is usually wet anyway from the nighttime dew. Direct water to the roots - not the top. When you water, direct water to the roots and avoid wetting the foliage of ornamental plants if possible. Drip or tickle irrigation or a soaker hose are efficient ways of watering. A timer installed on outdoor faucets to control the period of irrigation will prevent the unnecessary use of water.