Alan's guide to planting trees

• Best trees for small gardens

Planting bare-root trees

Deciduous trees that lose their leaves in autumn go into a kind of suspended animation. Their processes slow right down, which means that they can be dug up and transplanted (provided they are not hugely established) and moved with little check to their system. When large trees are to be moved they are generally ‘undercut’ with special machinery in the years before their upheaval so that they form a tighter rootball which will see them through the trauma of being shifted. Smaller trees – up to 2m or so – can usually be dug up with a modest amount of root and even if little soil clings to it they will most frequently grow away well come the spring, provided they are planted in good soil with a modicum of organic enrichment and not allowed to dry out before and during that big flush of spring growth.

The great advantage of bare-root trees is their value for money. Container-grown trees need more care and attention on the nursery and that is reflected in the price – they are always more expensive. The limitation with bare-root trees is that they must always be transplanted in the dormant season – generally between October and March. Evergreen trees are seldom sold ‘bare root’. You are more likely to discover that they have been ‘root balled’ and their roots wrapped in sacking or ‘burlap’ which is left in place at planting time to avoid the rootball falling apart. Early autumn is the best time to plant evergreens, rather than the dead of winter. The warmer soil at that time is better for their establishment.

How to plant container-grown trees

As distinct from trees grown in the ground in nursery rows, container-grown trees have spent their entire life in a large pot or flexible bag. As a result they have a compact root system which can be transplanted into a garden with very little disturbance, apart from the teasing out of any tightly wound roots in the interests of getting them to reach out into the surrounding soil. Their greatest advantage is that they can be planted out at any time of year, provided that weather conditions are suitable. Avoid periods of drought or freezing temperatures and make sure that the soil remains moist but well drained throughout their period of establishment. Their disadvantage is that they will be more expensive than those trees that are sold bare root.

How to plant trees in pots

Yes; it will have to be a decent sized pot or tub – preferably one at least 40cm in diameter – not only to provide enough sustenance for the roots but also to avoid rapid dehydration and to offer stability in windy conditions. Always use a soil-based compost, not only to add weight to combat strong winds, but also to hang on to nutrients longer – they are rapidly washed out in peat-free multipurpose composts.

Choose a tree that is relatively slow growing and which will, therefore, be happy with a relatively restricted root run. Japanese maples are the best bet here. I kept one in the same container for around 20 years, scraping away the surface compost each spring and adding a couple of inches of fresh to offer some degree of rejuvenation. Alternatively, knock the plant from the pot, remove some of the older compost and repot the tree in a fresh mix. My compost of choice is John Innes No.3 100% peat free – the peat fraction of the traditional John Innes compost having been replaced with alternative organic matter. The larger the pot or the tub the longer you will be able to keep a tree confined within it, though there is no reason why you should not move it up a few sizes as it grows, provided this presents no accommodation difficulties.

Remember that you alone are responsible for watering and feeding. Never let the compost dry out completely and give the tree a liquid feed once a fortnight between April and September. You can, if you wish, grow an oak tree in a pot, though you will find that within a few years it will rapidly outgrow the accommodation. Better to stick with things like the star magnolia (Magnolia stellata), Chinese dogwood (Cornus kousa) snowy mespilus (Amelanchier) and fruit trees grown on dwarfing rootstocks which will control their vigour. Generosity is the key to success – making sure that those supplies of food and water do not go short and that the potted trees are grown in a position which is well lit but sheltered from strong winds.

Alan Titchmarsh's favourite trees

Alan Titchmarsh reveals his all-time favourite trees, and why he loves them.