Winter Tree Care
By Lorraine Spooner
Whilst it is tempting to curl up in front of a roaring fire at this time of year, assuming the garden will take care of itself, this couldn’t be further from the truth. Our trees need our tender loving care during this harsh season, even when dormant, so below I have detailed numerous problems that could be happening behind your back and have recommended the appropriate tree therapy to help your plants survive.
After a wet, dull and mild December, we now have some bright sunshine and frosty mornings, so wrap up warm and venture outside to tackle these essential tasks – by being prepared and taking preventative action, you will reap the benefits and your trees will respond and love you so much more.
Winter burn
This refers to the browning of evergreen foliage, which occurs when the sun and/or the wind causes trees to transpire at a rate faster than their frozen roots are able to replace this lost water, resulting in dessication and browning of the plant tissue. Even on sunny winter days, warmth can initiate cellular activity, but if the temperature of a tree then drops to harmful levels at night, this newly formed tissue can die.
Winter burn can also damage bark, weaken branches, and may affect immature flower and fruit buds if freezing temperatures continue through to early spring. See paragraph below on ‘Protection’.
Frost heaving
Frost heaving occurs when soil freezes and thaws repeatedly. This pushes shallow-rooted plants out of the ground, exposing the roots. Ensure a thick layer of mulch is spread around vulnerable newly planted trees and shrubs which will provide essential soil insulation and retain moisture. Apply to the width of the canopy (or drip line) to ensure the fibrous roots are protected but avoid contact with the bark, as this can initiate decay. The applied mulch should look like a donut, with a hole in the middle for the trunk, not a volcano! If your plant has already fallen victim to frost heaving, replant and mulch once the soil thaws.
Wind rock
Wind rock occurs when the plant is repeatedly buffeted and the roots are disturbed enough to break the fine, microscopic root hairs. Even if the plant looks stable, without those fibrous roots remaining below soil level, take up of nutrition and, more essentially, water will be severely compromised. Follow the same guidelines as above under frost heaving to minimise this problem.
Roses are especially prone to wind rock, so reduce the height of your shrub roses by correct pruning https://www.rhs.org.uk/plants/roses/shrub/pruning-guide
If your tree has been adequately staked to the recommended height on planting, this will help in the prevention of frost heave and wind rock. All stakes and ties should be checked regularly to ensure they are not restricting tree stems as their girths expand. Allowing the tree some flexibility of movement is advisable, as this will encourage good root establishment and growth. Tree belts and ties are also a favoured overwintering habitat for pests, so check and remove before they have a chance to breed in the spring.
Protection
Wrapping to the base of the plant can lock in warmth, protecting the roots from freezing. Use stakes or canes as a framework to hold the fleece or other material away from delicate branches to prevent damage; wrap from top to bottom so that moisture does not collect in the folds of the material. Move tender containerised trees and shrubs under cover where possible, or group closely together against a house wall to create a mini micro-climate between them to keep them warm and cosy.
Thick snow can provide an insulating blanket to low growing plants if left undisturbed; however, this should be removed from tree branches if the weight is likely to cause breakage and damage the understorey. Conifers are particularly vulnerable so brush the snow off carefully by hand or use a soft bristled broom.
Deer and small mammals eat tree bark and branches to survive the winter when other food sources are scarce. This exposes and damages the cambium, a thin growth layer of the bark which makes new cells during the growing season that become part of the phloem and xylem tissues. Install tree guards or preformed net protection supported by stakes, appropriate to the animal. We now stock bio-degradable spiral guards – call the Plant Centre Office on 01869 340342 Option 1, for further information on our range of tree protection options.
Winter drought
This is difficult to comprehend following the recent wet December, but drought is a very common problem for trees during the winter months, when they are unable to draw up water from frozen ground; evergreens and newly planted trees are at most risk of this problem. If the weather is unseasonally dry, then soil moisture levels of your trees need to be checked frequently; follow this link for advice and remedial action NICHOLSONS Planting and Watering Guidelines.pdf then apply a thick mulch for protection and moisture retention.
Pruning
This is one of the most enjoyable of winter tasks, with fruit trees especially benefitting, to encourage fruiting spurs for bountiful harvests. If the weather doesn’t look inviting, fast forward to Spring and daydream – all that blossom buzzing with pollinating insects will be the result of your efforts. Winter pruning is mainly for apples, pears and quince (pome fruit); do not prune stone fruit, such as plums and cherries, at this time of year, to prevent fungal diseases taking hold through pruning cuts.
All trees will benefit from formative pruning in their early years to establish a good shape and what better time to see their structure when they are laid bare in winter. Remove all dead, damaged, diseased, or chafing branches, and those growing towards the centre of the canopy, cutting back the rest by a third; aim for an open goblet shape to allow plenty of airflow through the branches and penetration of sunlight for fruit ripening. Trained fruit trees should be pruned in the spring before bud break and again in the summer, to maintain their shape and maximise cropping.
It is essential to make the cut in the right place. Bad pruning – cutting too close or too far from a bud or at the incorrect angle – can result in die-back, bud damage (preventing it growing into a leaf or flower) and can also affect wound recovery. Make your cut just above an outward facing bud, sloping away from it to facilitate water run-off and allow the wound to callous over more quickly before active growth begins again in the spring.
Follow this link for more information https://www.rhs.org.uk/fruit/apples/winter-pruning
If your trees are mature and you’ve noticed damaged or broken branches out of reach, or they have just become too big for their allotted space, then call in the experts in our Arboriculture Department by contacting bev@nicholsonsgb.com Exposure to winter elements can cause damaged branches to break off completely, leaving trees vulnerable to infection and this also poses a safety threat. All is not lost, even neglected trees can be rejuvenated by Nicholsons’ professionals!
Hibernating Pests
‘Winter washing’ fruit trees can help control pests and diseases by removing overwintering eggs and debris and reducing fungal spores, which might be hidden in cracks and fissures in the bark; it is especially useful for controlling woolly aphids on fruit trees. However, bear in mind that other hibernating beneficial wildlife may be affected, such as queen wasps and ladybirds. Apples, pears, plums, cherries, blackberries, blackcurrants and grapevines can all be treated. Winter Wash is an organic mixture of plant oils, available as a concentrate for dilution in most garden centres.
If you would like any further information, please do not hesitate to contact me lorraine@nicholsonsgb.com Enjoy your winter garden 😊
