Sitting pretty: Show off your plants to their very best with some well-chosen ornaments

Placing objects so they look their best in a garden is more difficult than, say, wandering round your sitting room with a new picture to hang. What with windows, doors, fireplaces, built-in cupboards, sofas and suchlike, your options forwall space are limited. In a garden, even a titchy one, you can stumble for days with your arms round the bosom of a production-line Venus, looking for the right place to set it down.

But though, on their own, they cannot resolve the inherent problems of a badly designed and laid-out garden, beautiful ornaments certainly help to redeem them. They distract attention from things you do not want to look at. By setting eye-catching objects in certain places, you manipulate the way that your eye travels round your patch. A well-placed pot, seat, bust, urn, birdhouse or arch will force you to pause, while you take it in. These are the equivalent of the semicolons and full stops that crop up like oases in deserts of poorly punctuated prose.

Whatever this object might be, it should be worth looking at. If the eye is to be drawn, it must feel it has been worth the journey. As far as I am concerned, this rules out boys peeing in pools, nymphs and nymphets, goblins (though I am very fond of gnomes), anything in white plastic and any wood structure stained garden-centre orange. But I would defend to the death a gardener's right to have these things if they gave him or her pleasure.

Scale is important. So is line and texture. Objects in a garden are more often too small than too big. Big does not always equal expensive and, like tubes of toothpaste, the bigger you buy, the fewer pence per cubic inch you spend. One huge urn in a small courtyard garden can be breathtakingly good – if it is in the right place.

If you are playing games with scale, as when you put a disproportionately large object in a small space, you do not want to compound the shock by placing it in too obvious a place. So I would not think of putting a huge urn or pot or sculpture in the middle of a small courtyard garden, but towards the back, to one side, where it could be trailed over by some rambling rose escaping from a boundary wall.

If you come into your back garden from one side, as you so often do in town gardens, down a narrow passage, I would have the urn (or whatever) in the corner diagonally opposite. If it is directly in line with the way you arrive into the garden, your eye will go straight to it and the bulk of the garden to the side of that narrow sight- line will be cancelled out.

Objects can be asymmetrically placed in a garden and work particularly well like this if a garden is long and thin. You can balance the bulk of a sculpture or sundial or olive jar, by planting an equally bulky shrub, such as osmanthus, to balance it on the other side. You wouldn't put it opposite of course, but further down the length of the garden. In that way, your eye, instead of zooming straight to the end of the long corridor, will zigzag down the space, taking in the incidents placed to left and right.

Objects in a garden will often be set against a complex background and you will usually be looking at them from more than one angle. You must be able to "read" the line of the object against its backdrop, which is why simple shapes such as olive jars are so successful. The reverse happens in grand gardens, where complex Italian statuary reads best against cool simple backdrops of dark, clipped yew. For the Tuscan look, try Italian Terrace on 01284 789666 (italianterrace.co.uk).

Texture, too, has to work hand in hand with setting. In a shady corner, where the surrounding foliage sops up light (as yew does), you could use an ornament of shiny stainless steel to great effect. In full sun, it would be blindingly unsoothing. Texture has a lot to do with one's overall style. Wicker, rattan, terracotta all have the same homely quality. Rust is good, and very sexy, since Tom Stuart-Smith started using sheets of carefully rusted Corten steel in his prize-winning Chelsea gardens. Galvanised metal is for those who like Smeg kitchens and stainless-steel flashbacks, as my peerless mother-in-law called them. If you're not ready for a totally modern makeover, try a rusted metal arbour from Secret Gardens on 020-8464 5327 (secretgardenfurniture.com) or sculptures of reclaimed metal from the Baobab Trading Co on 01728 861889 (baobabtrading.co.uk).

The aim, always, must be to include objects in the party rather than impose them on it. A well-placed urn or statue should be rooted into the garden's design. A self-conscious ornament is a solecism. As well as looking comfortable, it must look inevitable. It should not look as though it has been dropped by a passing auk.

Geometric styles dictate more clearly than free-form ones where objects should go. In a garden of straight lines, ornaments can be set where paths cross, or where they end. In a design of swirls and curves, you do not want anything to disrupt the flow. Your planting perhaps will be brought out in promontories, shielding an object from view until you have rounded a corner.

Some objects, such as finely glazed ceramic jars in celadon red or Rupert Spira blue, need to look fresh and crisp. Scrub them regularly to retain their gloss. But stone urns, like luggage, should never look new. A bit of batter adds a touch of class. Unfortunately, it also ups the cost. If real stone is beyond your price, buy reproductions and either bury them for a while in the compost heap, or wash them over with milk or yoghurt to encourage friendly lichens. A bath in liquid manure is an even better way of encouraging the aged look that dealers call patina.

Not all urns are for planting. Some are for leaning on, some for writing odes to, others furnish vistas, even if the vista is only 10 metres long. Some run the risk of becoming expensive litter bins. If you live with someone who doesn't know an urn from an ashtray, raise the urn up on an Olympian plinth, far from the sordid detritus of everyday life. Ferns planted round the base will soften the outline and stop the thing shrieking "look at me" to anyone loitering. For understated ceramic ornaments, try Lucy Smith on 020-8558 4734 (lucysmith.org.uk).

Very shallow urns or other containers should certainly be left unplanted. Sometimes you can use such a container as a miniature reflecting pool, filled to the brim with water. But you must fish out debris on a regular basis. When you gaze into it, you should see the sky, not rotting privet or drowning wasps.

Whippets are classy companions in a garden, whether in the flesh or in stone. In this case, two is twice as good as one, lying either side of some steps perhaps, or gazing moodily over the lawn. You have to live up to whippets though: champagne not cider, rare schizandra, not red salvia. If you feel this would be a strain, try a monster acorn instead – much less demanding. The Landscape Ornament Company (01380 840533) has them, along with other fruit.

The best decorative containers for planting are neither too deep nor too shallow. For the best in frost-proof terracotta try Whichford Pottery on 01808 684416 (whichfordpottery.com). Portland stone, either real or reconstituted, ages to a pleasing greenish-grey colour, a good foil for plants. Tulips are naturals for urns, dark mahogany 'Abu Hassan' or one of the shorter Kaufmanniana hybrids. Either of these can be whipped out by the end of May and replaced with a second display for the summer: purple heliotrope with pale antirrhinum, Fuchsia 'Thalia' intertwined with nasturtiums, helichrysum intertwined with anything. The great thing is not to be in awe of your garden ornaments. Make sure they earn their keep.