My wife and I just bought a property and I don't know anything about plants or trees. Can someone tell me what the large trees/bushes/plants are and also how often do I need to water them?
Judging by the new growth being red, I'd say these were Photinia fraserii 'Red Robin'. I can't tell if they're pleached or not, can't see any framework within the foliage, so its possible they're just trained by pruning to this shape. Unless you live somewhere that gets very hot and very dry in summer, they shouldn't need much watering because they have access to the soil beneath the paving, and they're obviously already fairly mature plants - unless, that is, the former owners bought them recently as mature plants for 'instant' effect, which is possible if this is a recent property sale. If that's the case, they should be watered whenever the weather becomes hot and dry for a week or so, giving them a few gallons twice a week.
What you will need to do, though, is keep them pruned to maintain the shape and form they've currently got - left to its own devices, a Photinia will grow into a small tree of about 20-25 feet, with the usual 'crown' shape. You will probably need to trim back at least twice a year, maybe more. You should probably remove the short stems already appearing on the lower trunks of the plants by cutting them off close to the trunk with a clean and sharp pair of secateurs, up to the level of the more dense, top foliage, to keep the trunk areas visible and allow for other plants to have some light beneath. To the left of the picture, there looks to be a shoot or branch coming up from the ground, or possibly from the base of that particular plant - I'd clip that out too, but you'll need a good sharp pair of loppers for something that thick.