Tony Dickerson problem solves
Q How can we restore our flooded bay tree back to good health? Lucy Spokes, Morden, Surrey
A The flooding in summer two years ago would be particularly damaging. It limits oxygen supply to roots and prevents carbon dioxide diffusing away. Root function is reduced or stops and the roots start to die off, allowing the invasion of rots and decay. Top growth will then die or thin as the leaves and stems are unable to obtain enough water and nutrients. In cold winter soils roots respire little so flooding is much less damaging than during summer, when roots respire freely and need more oxygen. Few plants can survive summer waterlogging unless they’ve special roots, such as willows, adapted to such conditions. To start to restore your bay tree to health at this time of year it would be useful to improve aeration with a garden fork, inserted to a full depth every 10cm (4in) and pushed back to open up the soil. This needs to be done over the entire root area to 1m (3¼ft) beyond the canopy. Better still, lift the turf and create a vegetation-free area beneath the tree and apply a mulch to 10cm (4in) deep.
Next spring, once you see signs of new leaf growth, you need to prune the canopy back by 50 per cent to balance it with the reduced root area. This may involve pruning some branches out entirely but others can be reduced, always pruning to a well-placed side branch.
Apply a general purpose fertiliser, such as Growmore. If you haven’t lifted the turf, use a soil auger or bulb planter to create holes 30cm (1ft) deep and 30cm (1ft) apart and trickle an egg cup of fertiliser in before refilling with soil as otherwise much of the benefit goes to the lawn and not the tree. Water thoroughly in dry spells once a week.
Short-lived flash floods after a downpour seldom harm most plants. It’s prolonged, saturated soil that causes the most damage. Keep off areas which have been flooded until workable to avoid compaction and worsening conditions.
Consider installing a drainage system if waterlogging is a long-term problem. This depends on having somewhere for water to go, such as creating a seasonal pond at the lowest part of the garden to catch surplus water and let it soak in slowly, as it isn’t possible to connect to municipal drains.