Trees

Trees can bring so much to a garden, including shade, fruit, autumn colour, fragrance, flowers, height; and also offer very valuable environmental benefits. After the first year or two, trees need little maintenance or pruning and usually look after themselves with just a little routine care. If well chosen and managed, their ultimate stature and spread should not become an embarrassment.

Avenue of lime trees

Quick facts

Group Trees
Planting time October to April
Height and spread Varies
Aspect Sun, part shade and shade
Hardiness Fully hardy to tender
Difficulty Easy to difficult

Cultivation notes

Tree planting and establishment

Choosing good quality specimens, planting them correctly and looking after them for the first two years are crucial to successful tree establishment.

Other things to consider;

  • It is important to choose species suited to local conditions, such as soil type and exposure
  • Find out what the expected height and spread will be; chose one that will not outgrow the space available
  • Buy good quality, healthy trees with a well-balanced branch system. If grafted, the union should be well-healed. Check for obvious signs of damage to the trunk. Avoid trees with long circling roots or where thick roots protrude through the drainage holes of their container
  • Specimen, semi-mature or other large trees are much harder to establish than the smaller trees sold in garden centres, and these in turn require more care when planting than the 1.2m (4ft) young trees often called whips and available from specialist nurseries. This applies equally to existing trees that are being transplanted as to newly purchased specimens

Routine maintenance

Feeding: There is no need to apply fertiliser in the first growing season. The roots should be encouraged to grow out into the surrounding soil in search of nutrients and moisture to establish a healthy root system. On infertile soils, feeding the year after planting may be beneficial. Apply a balanced, general-purpose feed over the entire root area at about 70g per square metre (2oz per square yard) in the spring.

Watering: During the first two seasons after planting, newly planted trees require thorough watering in dry spells to ensure that the water reaches the full depth of the root system. The quantity required will vary with soil type but typically 30-50 litres per square metre (4-6 watering cans) each week in dry weather will be necessary.

Well established trees should not need to be watered, except in very severe drought.

Weeding: Grasses and weeds compete with young trees for nutrients, light and especially moisture in the first five years after planting. If planting in a lawn leave a circle of  at least 90cm (3ft) diameter free from turf as competing grass can seriously affect establishment and later growth.

Once established, weed control and underplanting is less potentially damaging as the developing tree will deprive competing plants of light and moisture.

Mulching: Trees, especially newly planted ones, benefit from mulching to suppress weeds, provide nutrients, support the growth of mycorrhizal fungi, improve soil conditions and conserve moisture. Trees are usually mulched in late winter, after any fertiliser application, to conserve winter moisture reserves in the soil before the spring and summer.

Suitable mulches include woven polypropylene or proprietary tree mulch mats. Organic mulches include bark mulch, leafmould or well-rotted manure. While clear of weeds apply a mulch 7.5cm (3in) thick over the root area (a minimum of 50-75cm (20-30in) in diameter). Draw the mulch back 10-15cm (4-6in) from the base of the stem to prevent rotting.

Adjusting ties and removing stakes: Inspect tree ties in spring and autumn and adjust ties to prevent constriction of the stem. After two growing seasons the tree should make sufficient root growth to anchor the tree and the stake can be removed.

Reversion and Sporting:  Remove reverted (in variegated trees) or sported shoots promptly.

Suckers: Remove any shoots arising from below grafts or from the roots.

Pruning and training

Young trees often benefit from some initial formative pruning:

  1. Remove congested shoots and ones that rub and any weak growth to make a balanced and attractive small tree. Also remove competing leaders. Do this in winter.
  2. To make a standard tree (lollipop shaped with a bare trunk) in winter remove sideshoots (laterals) from the lower third of the young tree and also any weak or competing shoots at the top of the tree.
  3. In later years gradually remove the lowest sideshoots from the bottom third of the tree, and shorten by half the remaining ones on the middle third in winter.
  4. Go on developing the clean stem until it is tall enough for your needs and then it is possible to make a tall tree with a centre leading shoot or a spreading tree (called an open-centred tree) by removing the leader by cutting back to a healthy shoot.
  5. After this initial pruning annual pruning is not usually needed, but from time to time remedial action might be taken to remedy storm damage, uneven growth or other problems.

For more, see our page on pruning established trees.

Propagation

Most garden trees are cultivars are propagated by grafting or budding (chip budding or T-budding) as they do not come true from seeds.

Many trees, especially species, can be raised from seed.

Others can be raised from softwood, semi-ripe or hardwood cuttings.

Cultivar Selection

View and choose from the vast array of trees offered on the RHS Find a Plant. Narrow the search to suit your needs; by size, evergreen or deciduous, season of interest, etc.

Trees for small gardens or wet soils are particularly valuable. Also see our page on birch for winter interest.

Links

RHS Find a Plant
AGM plants

Problems

Trees are large, slow-growing and therefore hard-to-replace features in gardens. Happily trees have evolved to withstand disease by compartmentalising diseased portions. All the same, ill health is a worry. Brown leaves on trees can mean a number of problems. Yellow leaves (chlorosis) indicate a nutrient deficiency or more often a soil structure or moisture problem. Newly planted trees have their own set of problems.

Trees can also suffer attack from pests and diseases such as honey fungus, silver leaf, bacterial canker, phythophthora root rot and verticillium wilt.

Bleeding from pruning cuts may be problematic on a number of tree species, including Acer, walnut and birch.

Unfortunately, trees can sometimes fail. Consider the common reasons trees and shrubs die. And consider getting in an expert arborist to inspect the tree.

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