Borders that work.

Most disappointing borders are simply too narrow. A 600mm strip along a fence can hold one row of things, which means no layering, no succession and nowhere for a shrub to sit behind a perennial. Before choosing anything, redraw the bed: 1.2 metres is a working minimum for a mixed border, 1.8 to 2.5 metres is where they start to look like the photographs. Taking that depth out of a lawn almost always improves the lawn too, because what is left is a clean shape rather than a leftover.

Dig three holes in different parts of the bed, a spade deep. You are looking for what the soil does when you squeeze it, how far down the roots and worms go, and whether the hole still holds water an hour after you have filled it. Much of west Kent sits on clay over chalk or greensand, which means different halves of the same garden can behave completely differently. Everything else on this page depends on getting that answer right, and no amount of compost turns a wet clay corner into a gravel garden.

Put the evergreen and woody structure on the plan before anything that flowers: a few clipped shapes, a multi-stem tree or a large shrub to anchor a corner, an evergreen or two repeated along the length. This is the part that is doing the work in February when nothing is in flower, and it is the part people leave out because it is not what is on the trolley in June. Get the structure right and the border still looks deliberate for the four months a year nothing much is happening.

The single biggest difference between a designed border and a hobbyist one is repetition. Three of something, used five times along the border, reads as a scheme. One of everything reads as a collection — interesting up close, restless from the house. Pick a short list, buy them in odd-numbered groups, and repeat them down the bed. It is cheaper as well, because you are buying fewer varieties in bigger quantities.

Weeds appear where there is bare soil and light. Planting at a spacing that lets the perennials knit together within two seasons is the most effective weed control there is, and far more pleasant than a membrane under gravel. As a rough rule, most herbaceous perennials go at five to seven per square metre, grasses a little wider, and ground-cover tighter still. Mulch the first two springs while it fills in, then stop — established, dense planting mulches itself.

Autumn is the best planting window in this country for most things. The soil is still warm, the rain does the watering for you, and roots get established over winter so the plant goes into spring ready to grow rather than ready to sulk. Spring planting works, but it commits you to watering through the first summer, and the first summer is always the one people underestimate. Container-grown stock can go in most of the year — just avoid frozen ground and drought.