When people water at dusk or when it's dark, water sits on the foliage for many hours. This extended contact with moisture can promote fungi and other diseases. The solution of course is to water in the morning so the leaves have time to dry in the sun. But the choice of watering system depends on a few considerations.

Spray irrigation is great for large, flat surfaces such as lawns. It allows you to cover a large area easily and relatively quickly. Also, if you bury the irrigation lines, watering becomes even easier because all you have to do is flick a switch or place the sprayer on a timer. The downside is that spraying uses a lot of water, much of which is lost in runoff and evaporation. And it wets all the foliage you are watering which, again, can promote disease. In addition, it's not very precise; time has to be spent adjusting the sprinkler heads. Frequently other things, such as trees or lawn furniture, get wet.

Drip irrigation has many advantages. It is easy to target a specific spot such as a root ball for watering. Runoff and evaporation are minimized, so a lot less water is used. The water flow can be controlled to deliver the water more slowly, which the plants will like. And drip irrigation can also be placed on a timer.

But since they are so targeted, drip irrigation systems can’t provide coverage for a large area. Using them in a big space is extremely time-consuming, because you constantly have to move and change the target spots. And all those drip lines create a tripping hazard.

It's best to look at each location and decide which watering method will work best there. For the home gardener, drip lines are usually short-term and specific. You can use them for new plantings until they get established or on a windy hillside where sprayed water would blow away or run down the hill. Since the amount and placement of water using drip lines is so specific, over time they become less effective. As plants grow, their roots expand away from the drip line, rendering it less useful. Even worse, roots may not grow because the soil outside the drip line area is so dry that no roots grow into it.

You will have to take all these factors into consideration (as well as costs) in deciding which method works best for your garden.

For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service