A garden hose is one of those necessary but not very attractive tools in a gardener's life. When not in use, it's a fairly simple matter to arrange a hiding place for your hose; when it is in use, you have a bit more work to do to hide it, but you can do so in a way that enhances your landscape as well as camouflaging your hose.
Purchase a green or black hose rather than a brighter color that will be more difficult to hide.
Install a garden hose holder on the wall near the faucet you use with the hose; a neatly wound hose is much easier to hide than a tangled, messy pile of hose spilling out everywhere.
Plant an evergreen bush in front of the garden hose holder. Supplement it with smaller deciduous shrubs or taller perennial flowers with broad foliage, such as canna lilies, to create a green cover for the faucet and garden hose when not in use.
Use an attractive, weather-proof container if planting is not an option around the garden hose holder. Simply detach the garden hose from the faucet, coil it neatly, and place it in the container when not in use.
Determine your garden hose route by laying the hose out in the way you most often use it when you need to leave it out for watering; if you have enough hose length, snake the hose next to the house or under shrubs and trees rather than pulling it across an open patch of lawn with no cover.
Mark the areas of the garden hose route that have no natural cover from shrubs, trees, outbuildings, fence lines, or other elements of the landscape.
Dig a very narrow trench along the garden hose route, which is in open lawn and cannot be covered by plantings. The trench should be only about 3 or 4 inches wide and 3 or 4 inches deep. Pat the soil down firmly to set the trench, sprinkle grass seed, and water thoroughly (use your hose!).
Plant ground covers along the garden hose route where it makes sense with the rest of the landscaping; these could be along the edges of flower beds, sidewalks, or outbuildings, under trees, or around shrubs or landscape features. If you want cover only in the growing season, plant any sort of annual or perennial ground cover that appeals to you. If you prefer cover year-round, choose an evergreen ground cover.
Follow your marked garden hose route every time you use your garden hose: Lay the hose in the trench you dug to keep it out of sight across the line, and wind it under the ground covers through the remainder of the route.