Flowers are classified as either annuals, perennials, and biennials. Annuals grow from seeds and flower their first and only year. Perennials grow from seed also and establish themselves the first year, but don't normally flower until the following year. These flowers will sometimes replant themselves and flower for many years to come. Biennials grow as a small plant during the year they are planted. In the second year they will bloom and then perish.
Like all plants, flowers have distinct preferences as to soil, light, water and temperature. For a flower to be successful in your landscape, it must be suited to your growing conditions and climate.
Soil: while it is true that flowers can grow just about anywhere, for a landscape garden you'll need loamy soil. Loamy soil has lots of organic matter, water percolates through it easily, yet it still retains enough moisture that plants can readily absorb through the roots. Since most urban soils are devoid of loamy soil, it means you'll want to start a program of amending your soil on an annual basis until it reaches that ideal texture.
Soil amendments means adding compost, some peat moss, maybe a little sand.
Mulching the flower beds also adds some organic matter over a period of years, as long as the mulch isn't too thick (less than 4")
Light: garden location dictates the type of flowers that can be grown in a particular spot. Flowers generally fall into 3 light categories: full sun, partial sun (sun/shade), and full shade.
Full sun means at least 6 full hours of sunlight (not 3 hours in the morning and 3 hours in the evening)
Partial sun means 3 - 6 hours of sunlight, but leaning slightly toward to the 6 hour mark
Partial shade also also means 3 - 6 hours of sunlight, but leaning more towards the 3 hour
Full shade means less than 3 hours of direct sunlight each day.
Adequate Moisture: flower's water needs depends on how much sun it gets, the type of flowers and the soil type. Some flowers need more water than others and some require less.
Suitable Temperature: almost all flowers are temperature sensitive and can not tolerate freezing temperatures. A few can tolerate cooler temperatures (i.e. pansies). You therefore want to be aware of the last frost date in your area and not plant sensitive plants (i.e. impatiens) until after that date.
Suitable Fertilizer: All plants require nutrients to grow. These are usually absorbed from the soil. Bacteria in the soil break down the organic matter in the soil and coverts it through their digestive process into basic elements such as nitrogen, phosphorous and potassium. Since this process is dependent upon the soil's microbes, if the microbes are missing for whatever reason, then additional nutrients needs to be added to the soil. This is done through adding fertilizer.
Fertilizer is processed compounds that have been reduced into a water-soluble format (meaning the elements will easily dissolve when water is added). This makes it easy for plants to absorb through the roots. Contrary to popular believe, fertilizer is not plant food. Plants make their food from sunlight. Fertilizers are the elements used by the plants to convert that sunlight into food that the plant uses to build new cells.
If you´re unsure of what type of soil you have, take a sample to your local garden center or county extension office and have a soil test made. Soil test kits are also available. Knowing whether your soil is acidic, sandy, or clay-based, can help you decide how to choose the right fertilizer for your flowerbeds.
After an individual flower head (not the plant) has bloomed and the petals have turned brown, it is usually a good idea to remove the spent bloom. This encourages additional flowers to develop and increases the overall fullness of the plant. This can usually be done with just a pinch using your finger nails, just below the flower head, or with clippers or scissors.