When soil is waterlogged, plants literally drown. Water fills all the air spaces between the soil particles and this prevents oxygen from reaching the roots. In turn, this causes the soil to stagnate and prevents root growth.
- plants may look like they need water because symptoms include yellowing leaves that wither and drop off. Wilting of the plant may also occur
- the surface of the soil is soaking wet with puddles on it
- when lifted, the plant roots are black, soft and soggy, and the soil smells of rotten eggs
- plant growth is stunted or plants fail to sprout and shoots die back
After prolonged rainfall, soil becomes waterlogged. And if walked on or driven over, the soil becomes compacted and drainage gets worse.
- water fails to drain away and puddles appear on the soil's surface
- soil turns to mud easily
- boggy lawns
Waterlogging and compaction can create ideal conditions for diseases such as phytopthora and other fungal attacks. For example, box is prone to box blight in poorly-drained sites.
- do not walk on wet soil because this aggravates compaction
- dig up waterlogged plants in pots, remove damaged parts of roots and replant in fresh, free-draining compost
- remove any dead or dying shoots
- spike lawns with a motorised spiker and add lime-free sand to improve drainage
- apply mulch over the root area
- feed during the growing season to encourage new root growth
- water regularly in dry spells because plants are more prone to drought stress after prolonged periods of waterlogging
- in clay soil, use plenty of organic matter and horticultural grit before planting to improve soil structure and drainage
- gently break down the sides of planting holes with a fork
- with free-draining soil, add organic matter to bulk up the soil and add nutrients, which would be washed away in heavy rains
- build raised beds and fill with well-drained topsoil
- install a drainage system or soakaway. Dig ditches filled with gravel to drain water away from the garden or talk to a builder about a pipe drainage system if the problem is more extreme
- put crocks in the bottom of pots and place them on feet to aid drainage
- do not overwater pot plants
Make the most of it
If poor drainage, flooding and waterlogging are persistent problems, it could be worth rethinking your planting scheme. Choose shrubs, trees and perennials that thrive in wet soil.
Trees and shrubs that do well in moist conditions include salix, cornus, betula, sambucus, liquidambar, ash and amelanchier.
Create a bog garden, which is good also for attracting wildlife. Plant irises, carex, gunnera, primulas, hostas, rheum and rodgersia.
If you are planning to lay a lawn, ensure the ground is not compacted and dig in plenty of organic matter, grit and sand before laying turf or sowing seeds.