Helen Yemm: why today I garden in pyjamas, not my nightie Allowed to ramble seemingly unaided up walls and fences, through and over other plants and features, carefully chosen so as to harmonise or contrast perfectly with their hosts, they create a magical effect - especially in small gardens where both drama and detail are so important. So much for the fantasy. In reality, what we generally end up with is an ill-thought-out mishmash of climbers that need different pruning care, planted in the wrong place with little or no support apart from each other, cantilevered out from the overburdened garden fence and causing damage in the neighbourly relations department. Climbers climb. Up and up. Many are woodland and hedgerow plants that, by various means, climb up host trees until they reach the sun - and pollinating insects - and then they flower. The host plants provide nutrients in the form of decayed fallen leaves, protect their young growth from strong, drying winds and also shade their far-reaching roots, which need cool, moist root runs and plenty of space. Now consider the average house wall or boundary. It will possibly be windswept, blisteringly hot and sunny or dank and shady, with dismal soil or indeed none at all at its base. Even if it is gorgeous old brick, you will very probably be anxious to grow something all over it. Fast. There may be trouble ahead. Do your homework If you grow smaller climbers up into existing mature shrubs, remember that the pruning rules apply to all shrubby plants, including climbers. For example, do not grow a group B clematis that needs minimal winter or spring pruning (more, and it won't flower) into a December-pruned climbing rose. Secondly, climbers need a good, deep root run. That is why most of them do really badly in pots. This is an undeniable fact and one that even experienced gardeners fail to come to grips with until they have squandered a small fortune. It is also heartbreaking, since so many gardens have blank walls and fences and no soil to plant in at their bases. Climbers in containers If there truly is no alternative, then grow non-rampant climbers in huge containers - half-barrels even - and remember that: a) a climber will only go up as long as it can go down; b) it must never, ever be allowed to dry out. Use a container that is as non-porous as possible and does not conduct heat well (wood is good; unglazed terracotta should be lined with plastic). Plant in John Innes No. 3 compost with a little extra organic stuff or multipurpose compost and with time-release fertiliser granules. Cover the soil with pebbles or cobbles to retain moisture. Do not be tempted to plant anything else in the pot with the climber or it will have to compete for water and food. If you must, stand pots of pretties on top of the pebble layer. This will jolly it up a bit, disguise the size of the container below and provide the major incumbent with a source of second-hand water and nutrients. Every year or so, remove the pebbles, scrape away a few inches of soil and replace them, adding food. With this gold-star treatment, you will probably succeed. Climbers in the ground Try to avoid shoehorning climbers into dry bits of scrubby soil where they have to compete for food, water and root space with their intended hosts. This is especially important if the hosts are already well established and will be robbing their young companions of all the necessities of life. If you are planting a climber - a rose or clematis, say - to go up a tree, try to plant it as far from the trunk as possible. I find that a branch pruned from the host tree, placed on the ground and leant against the tree's lower branches, to which you loosely tie the climber, provides the most natural way to "lead" it upwards. Remember, you will have to look at that support for a long time. In my view nothing is worse than an alien-looking bamboo cane. Once up in the lower branches of the tree, the climber will most likely find its own way up, but you should check from time to time. If it is struggling, lend a helping hand by wrapping a piece of chicken wire around a branch or tying stems in loosely. When planting near trees and shrubs, always, always, improve the soil in the planting area massively, digging down as deeply as you can, and mulch and feed for the first year while the newcomers are finding (or perhaps I should say burying) their feet. The absolute last word One last thing on the subject of climbers. You have been dreaming idly for weeks - throughout an entire summer, maybe - of seeing cascades of flowers of some heavenly scrambler tumbling elegantly from top to bottom of some otherwise unremarkable tree at the end of the garden. You know how it is; we all do it. Come planting time in the autumn (you don't know how you managed to show such self-discipline and wait this long), you drive 30 miles to the only nursery in your part of the country that stocks your wonderful whatever-it-is. You rush home, knowing already where you are going to plant it. Start digging. Shock horror. You manage with difficulty to dig 2ft down and still the soil is full of tree roots, dry as dust, frightful. You do what you have been told. Fill the hole with water - go off and do the crossword, drink a gallon of coffee in sympathy, whatever. More shock horror - an hour later the water hasn't drained. Oh woe, oh woe. Must be solid rock or clay underneath. Take my advice, plant your treasure somewhere else. You have just hit on the "planting site from hell" and the plan will never work. I write as one who knows. Climber/shrub twosomes that work Rosa 'Mermaid' (pale yellow) and Clematis 'Jackmanii Superba' (purple) Rhamnus alaternus 'Argenteovariegata' (variegated evergreen shrub) and Clematis 'Kermesina' (deep red) Rosa glauca (grey/purple leaves) and Clematis 'Madame Julia Correvon' (pink) Rosa 'Compassion' (apricot/pink) and Lonicera x heckrottii 'Gold Flame' (apricot/gold honeysuckle) Solanum crispum 'Glasnevin' (mauve/blue) and yellow nasturtiums. Clematis 'Perle d'Azur' (mauve/blue) and Vitis vinifera 'Purpurea' (purple-leaved vine). Vitis coignetiae 'Claret Cloak' (reddish-leaved vine) and Clematis 'Madame Julia Correvon' (pink). Lonicera periclymenum 'Graham Thomas' (pale yellow honeysuckle) and Clematis 'Perle d'Azur' (mauve/blue). Gardening in Pyjamas: Horticultural Enlightenment for Obsessive Dawn Raiders by Helen Yemm (Simon & Schuster, pub. April 11 2013) is available to pre-order from Telegraph Books (0844 871 1514) at £12.99 + £1.35 p&p