It is OK to water plants in the evening.
Plants and gardens are best watered in the evenings or in the early morning before the sun comes out or after the sun goes down.
Avoid watering your plants or garden in the hot summer heat as the plants can burn and the water can evaporate from the soil before it has time to reach the plants.
So water the plants or garden before the sun comes up or at least before noon or wait until evening as the sun gets less intense before watering your plants.
A garden can be planted over a septic tank drain field as long as you're careful with not digging into and damaging the septic tank drain field pipes.
When planting a garden over a septic drain field you have to be cautious about tilling and digging so as to avoid damage to the septic tank drain field pipes.
However the water that drains from the septic tank could be beneficial to the garden plants although you still will need to water your garden.
I planted a garden over my septic tank drain field and the garden seemed to grow much better than it did in other spots of the yard.
Herbaceous plants, such as annuals, perennials, bulbs and ornamental grasses are generally the best choices for use on a septic drain field.
Ornamental grasses also offer the advantages of having a fibrous root system that holds soil in place, and providing year-round cover.
To maintain the integrity and longevity of your drain field, you should never put anything heavy on top of any part of it.
You shouldn't even drive over the drain field, as the vehicle can crush the drain field lines.
Heavy items cause soil compaction.