Many times we buy plants on impulse then find there is nowhere in the garden that really suits them. Before buying plants carefully examine your garden to see how much sun and shade it gets, whether the soil is well drained or waterlogged and whether your aspect is sheltered or windswept. You'll then be equipped to go and buy the best plants for your situation; shade-loving plants for the sheltered areas, sun-lovers for the  warmspots,drought-resistant plants for the parched areas which may be either sunny or shaded, and swamp plants for the poorly-drained parts.

 But wait! Test your soil first, to determine the pH level of your soil and what kind of nutrients you need to add, if any. Is the soil acid or alkaline? Most plants prefer soil that is slightly acidic, but there are some that must have alkaline soil to grow.

You can alter the soil's pH level, but it's much easier to simply plant for the soil you have. Now you are ready to plant. Well - almost. Will you plant in groups or singly? If you buy 'one of everything' your garden may seem rather spotty. Group plantings are organized, harmonious and you can vary the color for interest.

Before planting out, place your chosen plants around the garden bed in their pots to see how they will look. Re-arrange them until you are satisfied. Grouping plants in sets of threes or fives usually looks better than planting in groups of even numbers. Be sure that you have an interesting combination of colors and textures of plants. Tall plants should go to the back or the center if your garden will be viewed equally from all sides. Try to keep your plants away from trees. The roots of trees are fiercely competitive and will steal all the nutrients and moisture meant for your flowers.

The right color scheme is one way to maintain the harmony in your garden. Imagine the color of the flowers when they are in bloom. Some colors may clash with others, but can still be planted side-by-side if they have a different blooming season. 

Foliage color is also important. Many flower plants have silver, grey or purplish foliage that is just as attractive as the flower.

This means that they are still attractive well past the blooming season and so have added value.