Some of the factors to consider when assessing your site conditions would be the hours of sunlight the area receives, wind exposure, soil composition and moisture levels. Taking the time to understand the area you are planning on planting up will help you make the right choices when selecting your plants. This will ensure a much higher success rate and reduce the amount of maintenance required to establish and maintain your wildflowers.
Determining the hours of sunlight an area receives, and when those hours are during the day, will help you understand what types of plants will thrive in that area and which ones will not. Morning sun, afternoon sun and late day sun are very different in the amount of heat intensity the area receives. Afternoon sun is of course the hottest and an area that comes into the sunlight in the afternoon after receiving no sun in the morning will experience a drastic rise in temperature. This is different than an area that receives morning sun, late day sun or both, in these instances the change in temperature is much less drastic but the hours of sunlight maybe the same.
Generally, more than six hours of sunlight would be considered Full Sun especially when that sunlight is afternoon sun. Part Shade might refer to an area with less than six hours of sunlight a day and most often early or late day sun. Light Shade indicates on and off sun during the day, examples of this would be areas in open woods or around shrubs and buildings that shade the area temporarily throughout the day. Shade would refer to an area that receives little or no sun and what sun it does receive would be early or late day sun or highly filtered sunlight like in a heavily treed area.
Exposure refers to the amount of protection, if any, that an area receives from surrounding trees, shrubs, buildings, hills etc. This protection is mostly from drying winds that melt snow cover in the winter and keep the humidity low in the summer. The exposure of a site is especially relevant in the Chinook Zone. Warm winter winds melt the snow cover and can cause die back of woody ornamentals due to the extreme fluctuations in temperature. Perennials can also be effected by lack of snow cover when their crowns are exposed and dry out or their roots freeze and thaw several times during the winter. Using perennial wildflowers that grow naturally in your area will go a long way to preventing this problem, but even in this case certain plants will not survive without snow cover in the winter. For example prairie meadow plants like Brown-eyed Susan should be fine in an exposed area, plants that prefer an open wooded area like Paintbrushes will not like an exposed windy area that has no shelter.
Soil Composition & Moisture
Like most things in life, a good foundation is the most important thing when it comes to longevity in any situation. In the case of plants that foundation would be the soil. Every species of plant has soil conditions in which it will thrive, conditions in which it will survive and conditions it will not tolerate. Understanding what the soil is made of will help you understand what is happening in the soil and enable you to make better choices about which plants will grow in what type of soil.
There are basically three types of soil; sandy, loam and clay. You can determine what type of soil you are dealing with by picking up a small amount when it is evenly moist, but more dry than wet and examining it:
Dry Soils are usually sandy or gravelly, drain rapidly and never have standing water. Well Drained may have standing water for short periods after rain but it soon drains away. Moist Soils have good moisture reserves in the subsoil to carry them through the summer and may have standing water in the spring and fall, or after a heavy rain.You can amend your soil by adding compost, manure, sand, etc. and depending on the project you may want to either amend the soil or specifically choose plants that will grow well in the existing soil.