The main problem with most mature landscapes is overgrown shrubs which no longer enhance your home. They may have been sheared so they are all round balls or boxy hedges. They may have lost their leaves at the bottom because of overgrown top growth. In many cases, shrubs have grown together so they no longer have their individual shape or character.
Take a critical look at your landscape and make plans for some remodeling. Even if your landscape is relatively young, you may be able to see shrubs that will soon be overcrowded. You may be able to remove some of the extra ones before they have completely grown together. This will allow the remaining ones to retain their natural shape. Will some light pruning on remaining shrubs help before they become overgrown?
If it is too late to do anything but remove an entire row or group of shrubs, you may want to make some plans on what you will use as replacements. There are lots of books on plants and landscaping at the library.
Several years ago I was a regional consultant for a series of books on landscape plans published by Home Planners, Inc., which are now out of print. I found 3 of these books offered for sale as used books at amazon.com for as low as $2.99. Titles are: The Home Landscaper, The Backyard Landscaper, and Easy Care Landscape Plans.
One of the best books for plant selection is Sunset Western Garden book. It has the most complete selection of plants.
Full service nurseries and garden stores can help you select appropriate plants. Be sure to measure the height and width of planting areas. Replanting with plants which reach a mature size greater than their allotted space will result in the same problem a few years from now. A sketch on graph paper can be very helpful. Consider widening beds near buildings so that you can leave some space between shrubs and the building.
Limit the different kinds of shrubs you plant. In most cases clusters of 3 or more of the same shrub are more attractive than individuals. Individual specimen plants may combine well with clusters of other plants. Consult books on landscape design for ideas about attractive groupings. If you are planning to do extensive landscape remodeling, a landscape architect or landscape designer may be a good investment.