If your garden has a bleak look during winter months, you can cheer it up with beautiful colors by adding some plants that bloom durint the white season.
There are some trees, shrubs or plants that once planted (they are not usually part of the natural habitat) take over the soil and light resources preventing other (desired) species from developing.
If your garden is struggling with sandy soil there is good news. There are a lot of deciduous and coniferous plants that thrive in sandy soil. Check them out.