Planting trees near to houses and walls

The question of how close to your house to plant a tree is a complicated one. After a dry summer there is usually a rush of claims to insurance companies after subsidence occurs. The problems generally happen in areas where there is clay soil as tree roots can remove the water from the clay producing shrinkage. This shrinkage may result in movement of foundations and the walls which they support. Exact information is hard to give but it is possible to give a few generalisations. I take my information from a textbook on the subject - "Tree Roots and Buildings" by Cutler and Richardson published by Longman Scientific and Technical. They work from reported problems and give the distance from buildings within which 50% of the incidents occur. If the incidents occur close to a building for a particular species this is considered to be a less dangerous tree to plant than one which gives problems at a greater distance from the house. So Willows, Poplars, Oaks and Elms can give problems at far greater distances than Birches, Hollies, Apples Rowans, Pines, Yews, Magnolias, Laburnums, and Cherries.

It may be wise to consult your insurance company before you plant a large tree in your garden. Be aware however that they are likely to give a very conservatve reponse and that our towns and cities would have far fewer fine trees in them if insurance companies had been the arbiters of what to plant.

There is another way to look at this problem. In many countries street trees are planted into prepared planting pits along the sides of roads. These are effectively large sunken plantpots which allow space for tree roots to develop without interfering with buildings, drains or other services. If you are keen to plant a large tree into a space near to walls, buildings, or services it may be possible to create a pit. For large trees you would need a pit around 2m x 2m and 1m deep. This would have thick walls of blockwork or alternatively welded steel. You would be making an enormous container with drainage holes to prevent it turning into a sump or underground pool. It would be essential to ensure that the container can drain properly and so it is unlikely to work if the pit is dug into clay unless you can arrange good drainage through the clay and away.

In order to water the tree effectively and, almost as important, to allow air to the roots a perforated plastic tube around 50mm in diameter should be buried to the depth of the pit but with its inlet just above soil level. These are available from tree and landscape suppliers but you could improvise one from a length of drainage pipe.

If made well this should allow a tree to thrive in a limited space without danger to its surroundings.

I HAVE SEVERAL ACRES I WOULD LIKE TO PLANT WITH LARGE TREES. HOW SHOULD I START PLANTING TO ACHIEVE FAST RESULTS WITHOUT SPENDING A FORTUNE?

Many people want to create small woodlands or simply make their land more attractive but don't want to wait too long for results. In the past the reasons for planting woods were often different from today's reasons - for instance planting to produce valuable timber or cover for game. These days the reasons are more likely to be aesthetic as there is a general understanding that huge areas of woodland have been lost and the countryside looks poorer as a result. Landowners may also be inspired by the valuable habitats which woodlands can provide or the future use of managed woodlands as sources of biofuel.

The first place to start when considering planting a woodland is to try to ensure that the trees planted suit your environment. For residents of the UK it is straightforward to discover what is native to your area by entering the first three digits of your postcode into the appropriate part of the website www.nhm.ac.uk/nature-online/life/plants-fungi/postcode-plants which is a national database provided by the Natural History Museum. This excellent resource will tell you all the native plants, not just the trees, for your local area. You should then look at any particular problems which your land may provide for a growing tree. These would principally be problems of drainage, soil type and exposure. All three of these could vary within a very small area so that very damp or dry patches, extremely windy areas or local soil problems might produce situations which may not be obvious from the database. The soil for instance may have been compacted by building machinery or polluted by previous use. If any of these problems seem likely than a site visit from an expert may be necessary and soil samples may need to be taken and analysed. However if your site is fairly typical of your neighbourhood the database will give you a good idea of where to start in choosing trees (or for that matter hedges and smaller plants).

There are several varieties of trees known for the speed with which they grow. Poplars, Willows and Eucalyptus are amongst the commonest. Indeed Poplars are the fastest growing source of hardwood in the UK. These varieties may not give you the end result which you need especially if you have a vision of stately trees with large spreading crowns lasting through the centuries. If you imagine your land covered in large Oaks, Beeches, Ashes and the like you will need to take a longer term view. Planting a fast growing species to give an early effect, with these larger species growing more slowly next to them, one day to take over from them and shade them out, may be your best approach. Willow, Alder, Poplar, Sorbus (such as Rowans) and Birch will give you the fast growing "nursery crop" amongst which the giant trees of the future can develop. Willows and some Poplars can sometimes be grown successfully simply by sticking suitable branches straight into damp ground, though they will need protection from rabbits and deer.

Buying and planting these larger trees is not entirely straightforward as there are several options. Mature trees, up to 9m (30ft) tall, can be bought, transported and planted by experts but this is a pricey business. You will be spending thousands per tree and access for large machines will be necessary. Trees smaller than this can also be bought and planted in a similar way but sometimes they can also be dug up and moved using tree spades where suitable specimens are available locally. Moving trees can work out far cheaper than buying new, purpose grown specimens.

At the other end of the spectrum trees can easily and cheaply be bought as bare-rooted plants. As the name suggests these are smaller trees, usually up to around 3m (10ft) high, which have been dug up during late autumn and winter when their leaves have fallen off and they are dormant, and are sold with no soil attached to their roots. They can be a very cheap way to buy trees and they usually establish well but, despite the fact that they come into leaf in the following spring and appear healthyl, they may sit still in your soil for several years without making much growth. They are building up their reserves and growing roots during this time. It may be very frustrating to wait for them to start back into serious growth after several years.

More expensive, though often very reasonably priced, are rootballed trees. These are grown in open ground and are prepared for movement in advance of digging them up. When they are lifted their roots are surrounded by some of the soil which they have grown in and are then wrapped in hessian. They are transported like this and the tree, complete with rootball and hessian bag, is planted into the new ground. Over time the bag rots and the trees strart back into growth with less of the disturbance which bare-rooted trees have suffered. They generally establish and grow more effectively than bare-rooted specimens.

The final option is to plant more expensive trees grown in containers. The art of growing trees in pots and bags has advanced greatly in recent years as our understanding of the needs of trees, and especially their roots, has moved on. Container-grown trees up to a considerable size can now be bought though it becomes difficult, and a little dangerous, to plant by hand trees in containers larger than around 70-90litres. Back injuries can easily result. Plants larger than these sizes need to be moved and planted by machine. Having spent more on these container-grown plants, whose chances of survival and speed of growth are likely to be greater, it is well worth getting professionals to plant them and look after them. If however you wish to plant them yourself you can usually buy container grown trees around 3-4m high for around £75-£100. They can be delivered to you and can sit happily in their pots for a time, as long as you look after their needs for water and support, whilst you wait for a suitable time to plant them.

With all of these trees aftercare and planting will matter even more than choosing the right varieties. A dry period in the years before a tree has settled in can kill off any tree and poor planting can produce all sorts of problems.

SHOULD I REMOVE THE IVY FROM A TREE IN MY GARDEN?

There has always been a lot of controversy about the effect of Ivy on trees and whether it is a good idea to remove it or not. In the end your decision may depend on what you want from your tree - a classic uncluttered shape or a wildlife habitat and a more natural, woodland appearance.

Ivy is a native, evergreen climber able to thrive in very low light levels such as often exist on the woodland floor or underneath the canopy of a tree. It uses a tree as a means of support, a way of climbing from the darkness at the ground to the relatively higher light levels at the top of trees. When it arrives there it changes form and starts to produce differently shaped leaves as well as flowers and seeds. In the process it does not generally harm a healthy tree but may contribute towards removing light from the leaves of an old or dying tree. In addition some trees with lighter canopies, such as Ash, which let more light through may support larger Ivy plants but these are not expected to shorten the life of the tree. They may however make it more top heavy and likely to fall in a storm or they may disguise damage to the trunk or branches of a tree making it more dangerous. In woodland situations this may not matter but in private gardens, in parks or on roadsides consideration may need to be given to this. In addition you may feel that a tree covered in ivy does not look as good as one without.

Before taking the decision to remove Ivy from your tree however please consider that it creates an excellent wildlife habitat. As well as providing cover and food for a huge range of invertebrates (insects, spiders etc) it can give excellent roosting places to birds and bats, overwintering niches for butterflies and moths and, of course, nesting places for a range of birds.

if you decide to remove your Ivy it is generally done by cutting the plants low down. They rely entirely on their roots in the ground for nutrition, they do not take any from the tree, and so cutting the stems will kill the plant above. It will go dry and brown with time and can more easily be removed from the support of the tree.

To sum up, the decision on whether to remove the ivy will depend on what you want from your tree. If you want it for its form rather than its value as a habitat you may decide to remove the Ivy. In a woodland setting the choice is usually easier as the form of a tree grown in the relative open space of a park or garden is rarely achieved and you can appreciate the tree for its role in the woodland ecosystem.