A beautiful dense and healthy row of greenery, that is what everyone wants! To achieve this you need to consider several things including suitable watering.
Think about the planting stage
We cannot repeat this often enough: you need to take care when planting a hedge. Planting that is carried out badly will cause later problems with plant growth, vigor and esthetic appearance. It can also have important consequences for watering. If the ground has not been dug far enough on either side of the hedge then the plants will be forced to grow in compacted earth, and you will use a lot of water to irrigate it!
The different techniques
To water a hedge properly there are several solutions. In the old days a ditch was dug next to the hedge, it was about 1metre from the base of the plants and about 50cm deep (sometimes up to 1m). When the heavy rains arrived, it would fill up and act as a water reserve for the hedge. It is an ecological approach but takes up space and demands some maintenance (you need to cut back the grass and clear it out every so often). You could dig a trench about 20cm deep closer to the plants’ base (30cm for example) and fill it with water every now and again. However, it is only a worthwhile solution if you have a lot of water, as much will be wasted.
The most common solution today is to use an irrigation pipe along the base of the hedge. It can be a perforated pipe, simply laid on the ground. However, this will encourage the plants roots to stay near the surface, it is therefore better to bury it. Rather than a perforated pipe it is better to use a porous pipe that allows the water to soak into the earth slowly rather than drowning the surface from time to time.
Watering via a spray, using either a water cannon system or an oscillating sprinkler is to be discouraged for hedges (and for the rest of the garden). It wastes a huge amount of water and encourages leaf diseases, especially those that are fungus based.
The right amount
The amount of water needed depends on several factors: the type of soil, type of plant, the exposure of the hedge to drying influences such as the wind and sun. The less that the soil is able to retain water then the more often the watering must take place. Plants with thick green leaves (such as Holly, Palm Laurel, Portugal Laurel, Privet) as well as conifers need less watering than those with fine leaves (such as Hornbeam and flowering hedges). It is also worth noting that a flowering hedge planted in a clay soil will have the same water demands as a tougher leaved hedge that is planted in sandy soil! Where there is a lot of wind, the water requirements can be doubled, especially if the spot is exposed to the afternoon sun.
In all cases, it is best to water in the evening, this will allow the plants to benefit from a damp soil throughout the night. For ease, it is best to control the watering of a hedge via an electronic timer. Ensure that the system incorporates a rain sensor or humidity tester. If you do not then there is a risk of watering when it is raining. Not only will this waste water but it also will harm your hedge and possibly cause the roots to rot.