When it comes to soil and gardening you have a couple of choices:
Grow plants that fit your soil and cultural conditions
Amend the soil so it is suitable for a wider range of plants
No soil is perfect, but overall perennials are fairly adaptable. We would recommend that your soil:
Contain sufficient organic matter
Contain elements required for growth (nitrogen, phosphorous, potassium, and calcium)
Be free of weeds
While there are a number of natural elements that contribute to healthy plant growth, soil is the most critical element. It supports and feeds plants, and provides water and oxygen to roots. Loose, crumbly soil is easy to work with. It holds enough water to keep plants happy but drains quickly so they don't drown when it rains hard or for a long period of time.
No amount of additional water, fertilizer or TLC produces the same positive results as good soil preparation, so don't skimp on this step.
The way water moves through soil is called drainage. When water moves quickly through soil, the soil is described as well drained. When water moves slowly through the soil and pool on the surface, the soil is described as poorly drained. Poorly drained soil stays cold and wet in the spring, roots drown due to the lack of sub surface oxygen, and plants often rot in the winter because the soil stays too wet. Fortunately, most poorly drained soils can be improved by adding plenty of organic matter. In some cases you may want to improve drainage by building raised beds or terracing, then adding properly prepared soil.
How much moisture
The amount of moisture your planting site receives depends on many factors including slope, large trees, temperature, precipitation, soil type, physical barriers and groundwater. Large, shallow-rooted trees such as silver maples soak up huge amounts of moisture and nutrients, and create a situation known as "dry shade" which is an environment that doesn't support many other plants. On the other extreme, the bottoms of slopes often hold water for long periods of time, and are much wetter than surrounding soil.
Windy areas also tend to dry out faster than calm areas. If your property is plagued by high wind, you may want to consider planting a windbreak to break up the wind, and create a shelter for your plants.
Once you know how much sun, and how much moisture your planting area receives, you're ready to match the right plant to the right place.