Trees are the most important group of garden plants, providing shelter, privacy, shade and background greenery. They are beautiful for their shape, colour, texture and sheer physical bulk. They are ever-present, contributing in every season – the shape and colour of the trunk, limbs and twigs in winter; fresh green foliage, flowers and scent in spring and summer; and blazing colour in autumn.
When to Plant
Trees are sold either as container-grown or as field-grown, bare root plants. Container grown trees can be planted all the year round but the ideal period is during spring or autumn when there is still some heat in the soil to encourage rapid establishment. Trees planted during the late spring or summer months will need to be well watered, especially if a peat compost has been used. Bare root trees are best planted during the period from late October to mid-March. Evergreen trees are normally raised in containers and are best planted in April or September. On light soils autumn planting is recommended so that roots become established to take advantage of available soil moisture in the spring. On heavy wet soils and exposed sites, roots may rot during the winter and the plants suffer wind damage so it is best to plant in the spring.
Planting should never be done if the ground is very wet or frozen. Evergreens continue to lose moisture through their leaves during the winter and are prone to drying out. Planting evergreens must be avoided during spells of cold drying winds.
Where to plant
Plant trees where their shape can be appreciated and where they can grow unimpeded by other plants, walls or buildings. Trees are planted for a wide variety of reasons, such as to give height to a garden, for shelter, for privacy or to frame views. Where trees are planted depends on their function. Our strongest winds come from the south and west and shelter trees, such as Alder, should be planted where they will be most effective. Trees can be used to block off the view of a garden from neighbouring windows but too many in a small area will make the garden dark and dismal. Strategically planted upright growing trees such as Prunus ‘Amanogawa’ and Sorbus ‘Joseph Rock’ can provide privacy without being too oppressive. Tall growing forest trees or trees with invasive roots such as Popular or Willow should not be planted within 35 metres of the house and so are unsuitable for small gardens.
What to plant
Trees come in all shapes and sizes and may be planted for the beauty of their flowers, fruits, foliage, bark, scent or shape. In small gardens, plant trees that have several attractive features which will provide interest over a long period of time. A visit to a good garden centre, where a wide range of trees is on display, can be very helpful in making a wise choice. Trees that grow large, such as oak, ash, beech and cedar are only suitable for big gardens. Upright growing (columnar) types, such as Sorbus ‘Joseph Rock’, are very useful in small gardens. Where there is room for only one or two trees, choice types should be selected. Suitable trees for small gardens include June berry (flowers and autumn colour), mountain ash (spring flowers and autumn berries), White Himalayan birch (white bark) and Acer griseum (flaking bark and autumn colour).
How to plant
The success of trees depends on good planting. Trees that are planted badly may survive for 10 or 20 years but never thrive.
When planting trees, the correct sequence of operation is:
- dig the planting hole
- insert a stake in position (if staking is necessary)
- place the tree in the hole and back fill the hole with soil
- tie the tree securely to the stake
The planting holes should be at least twice the diameter of the container or root ball, so that the roots can be well spread and backfill soil can be worked in easily around them. Loosen the soil at the bottom and sides of the hole so that new roots will penetrate more easily. Any dead or diseased roots should be removed from bare root plants. Stand container-grown plants in water for half an hour before planting to ensure that the compost is thoroughly moist. If roots of container grown plants are matted or circling around the root ball, these should be gently teased out with fingers or hand fork to enable them to grow outwards into the surrounding soil.
Planting trees too deeply is a common mistake; trees must be planted at the same depth as they were growing previously in the container or field. As the soil is backfilled around the roots it should be firmed in stages by treading to remove air pockets. No fertiliser is necessary unless the soil is poor when a slow release fertiliser can be used as recommended.
Staking is usually unnecessary for small trees or for conifers