Start by drawing a plan of the existing bed or border on graph paper. Mark any existing trees or shrubs on it that you want to leave in their present position. If you plan to alter the shape or size of your border, now’s the time to draw in any changes.
Assess your conditions
Assess your site looking at sun and shade, soil type and pH to determine which plants will grow well. Mark on your plan any existing features that you can’t change, such as high walls or fences, or any large neighbouring trees that overhang the garden or buildings that cast shade. Also show north and south on your plan, so you can easily see how sun and shade will vary during the day. Check out the soil to see if it’s sandy (gritty textured, often pale-coloured, puddles vanish immediately after rain), clay (sticky when wet, sets like concrete when dry, puddles remain for hours or days), stony or reasonably good loam (crumbly texture when moist, a darkish colour indicates plenty of organic matter). Do a pH test using a meter or a small test kit to tell if your soil is alkaline, neutral or acid. (Both are inexpensive and available from garden centres)
Prepare to plant
Decide on a style for your border, to suit your house or your personal tastes. A traditional mixed border includes small ornamental trees, shrubs, roses, evergreens, perennial flowers and bulbs. A herbaceous border is mostly perennials and bulbs, while a cottage garden border is made up of largely self-seeding annuals, biennials and spreading perennials plus some bulbs, roses and flowering herbs. Contemporary styles make use of striking ornamental grasses, sedges and bamboos with a few architectural trees or shrubs, or you might go for a wildlife border with native shrubs and wildflowers.
Make a short list of plants that you want to grow, look them up in a plant encyclopaedia to see if they suit the conditions available, and begin sketching them in on your plan. Try out alternative plans before picking the best. Try laying a sheet of tracing paper over your original outline, so that you don’t have to redraw the basic plan every time.
Instead of trying to do a planting plan for a whole border all at once, choose groups of three plants at a time – one tall upright shape, one medium-sized domed or bushy shape and one low, wide-spreading shape will go well together. By alternating several trios, you fill a border with interest. In tiny gardens you can plant one at a time, grouping three or five plants of each type to striking effect.
Don’t be tempted to buy plants this early in the season; wait till spring when things are starting to grow. Meanwhile there’s lots of preparation to do...
Do your groundwork
As soon as the weather permits, dig out unwanted plants, roots-and-all. Remove any weeds and stones and work in lots of well-rotted organic matter so you’re ready to replant in spring. With luck, your new plan will put on a good show in its first year.