Your wall plants are going to be in place, it is to be hoped, for a long time so it is well worth while giving them the best possible start in life.
First, check the soil in which the plants are to grow. If it is in front of a brick-built wall, especially a new one, it may well be full of rubble and mortar which can actually alter the level of acidity or alkalinity of the ground and make it different from the rest of the garden, turning what appears to be an acid soil, for instance, into an alkaline one. There may also be brick or concrete footings and foundations in the way, which means that you may find you cannot dig very deeply and that the site is unsuitable for deep-rooting plants.
The ideal soil is one with a good amount of humus in it. This has several advantages. It will retain water, for instance, and stop the soil from drying out too quickly. This is not only a problem if your garden is sandy but with planting against walls in general, since they tend to shield the ground from the rain. Humus, whether it is in the form of farm manure,or peat, will improve every type of soil, helping to lighten sticky clay in particular and to give it better . And humus is especially necessary for soil near a brick wall, as the bricks, which are basically porous, tend to soak up all the moisture they can get from their surroundings. If you have walls facing south or west, which get a great deal of sunshine, the beds in front of them tend to dry out a great deal and they need humus too. So do not skimp on the quality of your soil: give it all the help that you can.
Make sure that you are putting your plants in the best possible place. Having checked that they are suitable for the aspect – north, south, east, or west-facing – there are other factors to take into account. Never plant anything close to a drain of any kind or you can be in for real trouble: thecan all too easily get down into it and cause plumbing difficulties. The same goes for anything that is invasive – ivy (hedera) or the Russian vine (Polygonum baldschuanicum),
for instance; do not plant these near drainpipes, especially the more pliable plastic variety, or you may have great difficulty in untangling them. Exposed corners of buildings are also tricky when it comes to siting a plant, for there are almost inevitably draughts whistling round them that will scorch the foliage. It is better by far to site the plant 90 cm-1.2 m (3-4 ft) to one side or the other, rather than on the corner itself. This applies especially to evergreens.
PREPARING FOR PLANTING
Do not make the all-too-common mistake of making a planting spot for your climbers and wall shrubs too close to the fence or wall. This has two disadvantages. First, the roots will be cramped because they will have what is virtually a semi-circle, rather than a circle, in which to spread themselves. Secondly, they will not get enough moisture if they are shielded too much by the wall behind them. Planting too close can also mean that the mainof a wall shrub does not get a chance to develop properly and, in the case of south- or west-facing walls, the very considerable heat that will be bounced back from them can even scorch tender or foliage. Many plants prefer a cool run, and they are less likely to get it if they are close to a wall. It is better in that case to plant them in the shade of other shrubs.
So make sure that your climber is put at least 15 cm (6 in) away from the wall but no farther out than about 30 cm (1 ft) or you will lose the protection that a fence gives. Wall shrubs, on the other hand, should be placed a little farther out, but no more than 90 cm (3 ft) away.
PLANTING IN WINTER
Extra care is needed if you are putting wall shrubs or climbers into the ground during the winter months – and it is not advisable to do this with evergreens, which are harder to get going than deciduous plants. If your climbers or shrubs are bought during cold frosty weather, do not attempt to put them in the ground at once. Instead, put them somewhere cool but frost proof – a garage, for instance – and leave them as they are if they are in containers, or make sure that the roots are well covered, if you have bought them bare-rooted. They will need very little water at this time.
If the weather is suitable for planting, but you do not have the proper site ready, the plants can be ‘heeled in’ for the time being: simply dig a trench in an odd corner of the garden, place them in it, spreading out the roots as you do so, and cover with soil. (This only applies to bare-rooted plants: those in containers can stay in them indefinitely.)
Never plant your climber or shrub on a really cold, frosty day, or when there is a cold wind. If you have to do so for some reason, make sure that the roots are not exposed: if you have to leave the plant for a while, cover the roots with a piece of sacking.
PUTTING IN THE PLANTS
If your climbers or shrubs come to you bare-rooted – and many hybrid roses are sold this way, wrapped in polythene – make sure that you dig a generous hole to take them. It should be possible to spread the roots out easily round the plant. Do not cheat by cramping them in, for the plant will take longer to become established. If you are staking your plant for any reason, the stake must be put in place first, otherwise you may spear vital roots. Make sure that you put your plant in at the correct depth. Too high, and some roots may be exposed on the surface with disastrous results; too low, and you could have all sorts of problems, especially if the plant is grafted. Look for a ‘tide mark’ of soil round the stem of the plant just above the roots, showing where it was planted in the nursery, and use that as your guide. When you are planting a wall tree or shrub, place it in the hole, shovel in some soil so that the roots are just covered, then give it a shake, to let the soil settle down between the roots, and add more on top. Finally, firm the soil round the plant by treading on it: that’s the easiest way. Keep an eye on recently planted shrubs and climbers during frost: quite often the soil may move and crack, leaving the roots exposed.
Container-grown plants or those that have been ‘balled’ -I.e., covered in a ball of hessian-need a different technique. You do not want to disturb them too much while planting them – the great advantage of container plants is that they suffer far less from transplanting-but you do want to encourage the roots eventually to venture from the original-ball. The best way to do this is to put plenty of peat and phosphate in the soil round them: phosphate is usually sold in garden centres in the form of bone meal or super-phosphate.
Before you put your container-grown plant into the ground, give it a good long soak in water. Plunge the container in a bucket of water until all bubbling stops, or, if you have the time, leave it like that for an hour or more while you prepare the site. If the plant is not in a flexible pot but in some sort of wrapping, cut it open carefully, making sure that you do not damage any roots that may be clinging to the sides. Having got your plant out of its container (remember not to do this in very cold weather unless you can put it into the ground almost at once), check the roots: if they are circling the root-ball, these outer roots can be gently un- ravelled: otherwise leave well alone. Put the plant in the hole – the level of the soil in the root-ball should be just about 2.5 cm (1 inch) below that of the garden. If the plant is in a ball of sacking (and many evergreens are sold this way),it in the planting place and, having checked that the level is right, cut away the hessian from the sides, leaving anything underneath the roots to rot away of its own accord. Finally, fill in the gaps round the root-ball with fresh soil and firm in in the usual way.
Keep an eye on your plants for the first week or so. Shrubs – especially evergreens – need a great deal of water to get them going and it pays to spray their, too, with water.
Don’t be surprised if your plants seem to make little or no progress at first. Some, like the Russian vine (Polygonum baldschuanicum) will spring into vigorous growth almost at once, while others – and the wisteria is notorious – ‘sulk’ for several months until you think that they may well be dead. To check whether your shrub is, in fact, dead or not, scrape the bark with a penknife, hoping that the surface will be green underneath. Try this low down on the plant rather than at the tip, which might have died off.
Never leave a newly planted climber or shrub to rock to and fro in the wind. Tie it up at once, otherwise the movement of the stem will disturb the roots just when they are settling down, and may eventually kill the plant.