Gardening: Garden extras hog the limelight

IN GARDENSPEAK, 'Nature abhors a vacuum' means 'weeds rush in where flowers fail to grow'. Here, white bladder campion pops up everywhere between new plants. As weeds go it is inoffensive, until you look it up and find that its natural habitat is waste ground. This is galling because hours of digging and barrow-loads of compost have been devoted to the preparation of the flower bed, its chosen resting place.

My new mixed borders, now in their second summer, are full of vacant places. The woodier plants have not yet expanded to fill their living quarters and expensive perennials such as peonies are still miniature versions of their ultimate selves. One day the choicer features will become more substantial but, until then, those destined to fade into the background are hogging the limelight. Hardy geraniums are not technically weeds, but some of them behave as though they were: the tiny dark-flowered G. phaeum reproduces misty versions of itself everywhere; the huge purplish blue G. magnificum sprawls about as though it owned the place; and pink G. endressii increases with determination into fat rooty clumps. I tolerate these in the absence of more distinguished plants, but cannot say that I would choose them for prime positions. Their better behaved versions are welcome to occupy as much space as they like: lavender blue 'Mayflower' was lovely for weeks; 'Kashmir White' is neat and low and looks right everywhere; and even though 'Mrs Kendall Clark' needs staking, her milky blue flowers are well worth the effort.

In a new border, the dilemma is always the same - do I now dig up the less choice plants and replace them with an infant rarity that will not fill the space and will probably be eaten by rabbits? Or do I leave the ground cover to keep the soil out of the grasp of campion and chickweed? Rich gardeners solve this problem by buying quantities of mature plants at the start. Clever gardeners propagate and 'grow on' the rare plants in nursery quarters until they are big enough to move. Impatient ones fill the gaps with thugs like geraniums or with annuals such as the green zinnia 'Envy', the white cosmos and the black-purple Malva sylvestris, as I do. This is showy the first summer, but not ideal if long-term plans are to be fulfilled.

In this flowery patch, the problem is made more acute by my reluctance to remove the pink, mauve or white gap-filling hesperis which have been flowering for more than six weeks. They smell delicious, but they have had their day. It is time to replace them with Verbena bonariensis. The quantities needed distort the colour scheme, subduing what ought to be a rich mixture down to a single hue. It is tempting to add splashes of colour but as the scale of plants to flowers changes and the fillers fade into the background, it will all need re-adjusting. As new plants, a small cistus in Fifties lipstick pink, or a peony in strong magenta, might be just what is needed to correct the colour balance but as they grow their contribution could become overwhelming.

Of course I could play safe, go for something that I know will work, but in this place I want to try rich red, cerise pink, purple and blue with silver, as well as white, all together. Some of the reds, like Lobelia cardinalis, are strong but it is not brightness so much as richness that I want here, so they have to be used with caution.

A lot of the gardening I do at this time of year involves standing about at different times of day holding up a flower and squinting past it to see if it will work with the group already in place. Colour is difficult to plan. Even if the colours were in the right places and proportions there would still be the plants' shapes and textures to bother about.

Some people think that the way plants grow and the look of their leaves are more important than the colour of their flowers. In a way they are, but there are rules for getting the plants in the right place that are easier to apply than any colour formula. Put simply, the trick is never to place two plants with the same kind of leaves next to one another because you waste their effect. For example, hemerocallis with sword leaves next to irises which are roughly the same shape, or lavender with thin grey leaves beside the roughly similar pinks, look dull and almost irritating. Had I been thinking of this I would not now find a meadowsweet next to a Jacob's ladder - both with cut leaves. Nor would I now be looking at a foaming crambe next to a giant yellow scabious. Their scale makes them hopeless companions. A good gardener once told me: 'Nobody gets a border right first time.' So all this tinkering and agonising is part of the pleasure of gardening.

Actually, nobody gets it right ever, except perhaps for a day or two a year. And just when everything is glowing and you ring up a gardening friend to say 'you must come, it really is looking rather good', the wind blows all night and the delphiniums - all 8ft of them - fall flat on their faces. Or the rabbits eat the campanulas, snails snack off the tops of the clematis and pigeons discover the seed-grown green sweet pea. Not content with filling the vacuum, Nature has ways of dealing with hubris.-

(Photograph omitted)