Causes and solutions
Poor root systems
Bare-root trees and shrubs lose most of their root system when lifted for transplanting. They have to grow new roots to survive. For these plants to survive, post-planting irrigation and weed control are crucial.
Remedy: Water newly planted trees and shrubs well, remembering that soil may be dry around the roots even when the surface appears moist. Weeds compete with plants for water, so keep a vegetation-free circle at least 1.2m (4ft) in diameter around the plant for its first three years to help avoid this problem.
Inadvertent frosting, waterlogging or drying of roots before planting reduces the chances of success.
Remedy: Keep newly purchased plants in a cool, but frost-free place, with their roots covered, until you can plant them. Plant bare-root trees and shrubs as soon as you can. If you can’t plant them straight away, heel them in until planting is possible.
Container grown trees and shrubs retain their root system, but container cultivation can lead to congested, curled roots which often fail to grow out into surrounding soil.
Remedy: Dig up the plant and uncurl the roots, cutting them if necessary, and spread them out in a new square planting hole. Try to avoid buying pot-bound plants, which are recognisable by a mossy covering to the compost and congested roots when tipped out of the pot.
Insufficient water
Insufficient watering in the first two years after planting is the main cause of poor establishment. Nearby trees, shrubs and hedges can also cast a rain shadow. They also have thirsty wide-ranging roots, leading to greater watering requirements than expected.
Remedy: Check moisture levels around roots with a trowel. Watering to soak the root zone requires at least the equivalent of four watering cans per square metre.
Weeds, lawns and other vegetation intercept water before it reaches the roots.
Remedy: Keep a circle at least 1.2m (4ft) in diameter around the base of the plant that is vegetation free for three years after planting, using hoeing, weedkillers or mulch.
In hot, dry weather, plants lose moisture very quickly.
Remedy: Cover the bare area around the base of the tree with a mulch of plastic sheeting or organic matter to help retain moisture and suppress weeds. Thick, coarse organic mulches are ideal, cooling the root systems and improving soil structure over time to create a well aerated but moist area where roots can survive winter waterlogging.
Wind rock
Wind rock of unsecured trees and shrubs can damage roots and lead to water collecting in the ‘socket’ caused by the stem moving at soil level. This can lead to fatal rotting.
Remedy: Staking avoids this, but stakes should be no taller than one-third of the stem height and must be secure. Avoid excessively tight tree ties when securing stems to stakes, prevent rubbing of stems against stakes and ties, and remember to progressively slacken the ties as the stems grow.
Plant nutrition
Although a lack of nutrients is seldom involved in establishment problems, it is worth applying a nutrient or fertiliser to the leaves (foliar feeding) in order to get some nutrients into the plant, even though its roots are not fully functional.
Remedy: Use special fertiliser formulated for foliar feeding, and spray in overcast weather to avoid scorching the foliage. Make sure to spray the undersides of the leaves as well. Fertiliser top dressings in late winter or early spring are worth trying where other factors are clearly not to blame for poor growth.
See the below links for more information on looking after newly plants trees and shrubs.
Links
Tree and shrub: planting
Mulching
Tree staking