Whether you live in a city with not much space outside, or have just run out of horizontal room, vertical gardening is a great solution.
On a trip to Switzerland and Germany, I was awestruck at the beauty of the window boxes, which are on almost all homes and many of the businesses. They add a huge amount of beauty to the cityscape and really punch up the welcome factor. I was truly heartened to see the level of care people take to keep them so full and healthy looking. You see them being watered and tended carefully throughout the day. On many lamp posts there are hanging baskets as well. Most hang on cables, allowing them to be lowered to be watered. These days, there are many small drip-irrigation attachments which can be hooked up to hoses, and even put on timers, which make this task a lot easier. They allow you to place the water emitters exactly where you want them so the whole basket/box gets watered evenly.
Even walking through the narrow streets and alleyways, you see gorgeous examples of vertical gardening — hanging baskets, trailing vines, window boxes cascading with flowers.
In my own garden I have been training a pyracantha as an espalier to cover a wall next to my back walkway. Also, a couple of wisteria vines on arbors and a hummingbird vine onto a rail of the deck. Most recently I purchased a fig tree from a cultivar grown at Mt. Vernon. It has now grown big enough that I can start to train it as an espalier, which I hope to plant, and attach it to the chimney on the east facing side of my house. My goal is for the pyracantha to completely cover the wall in a solid mass. The fig will be trained in a more open design, allowing the branches more horizontal growth with space between. This makes it easier to pick the fruit.
When creating an espalier, you can easily train the plant on a wooden or metal frame when they are small and still in a pot, then transplant to its permanent location as it matures. I find that masonry anchors work best when attaching the plant to my house (brick), but if you have siding there are many clips designed for this purpose. I just attach to the anchors with twist ties. On the wall I am trying to cover completely, I have a number of wires which run horizontally, and I attach the branches to them. This cuts down on the number of anchor you need.
Many vines will attach themselves without any anchors, by twisting around their supports (like wisteria), but be careful of vines with little roots (like ivy) which can literally destroy mortar and siding. Another tip is to make sure that the arbor is strong enough to take the weight of the vine. They can get quite heavy, and when coupled with a wind or rain storm, it needs to be secured strongly to take the weight. I had one topple over with a hummingbird vine attached to it a few years ago, but found that securing it with tent spikes helped during bad weather.
My last tip is for extra hydration during the hottest of summer days. Placing a handful or two of ice cubes around the base of flowers in hanging baskets or window boxes will help them to slowly absorb extra moisture and keep their roots a little cooler. This also works great in pots. Stay cool, and enjoy the beauty.