From the Royal Horticulture Society
Few garden plants will survive water-logging or flooding. Prolonged periods of sitting in ground saturated with water causes yellow leaves, root rot and death. However, conditions can be improved using various techniques to promote drainage and prevent damage.
Quick Facts
- Common name for this problem: Waterlogged or badly drained soil
- Plants affected: All except a few tolerant ones
- Main causes: Heavy rain combined with difficult soil conditions
- Main symptoms: Yellow leaves, rotting roots, stunted plant growth
- Timing: Winter and summer
What Is Plant Water-logging?
Soils become waterlogged when water builds up, unable to drain away. This leaves no air spaces in the saturated soil, and plant roots literally drown. Serpico Landscaping’s teams can help correct drainage problems from compacted soil, as a service for spring and fall, especially smart for spring 2017!
Short-lived flash floods after a downpour seldom harm most plants. It is prolonged, saturated soil that cause the most damage.
Symptoms
Symptoms of water-logging are not easy to tell from other disorders but look for the following:
- The first symptoms appear on the leaves. This includes yellowing or decay between the veins, resulting in soft areas at the base or centre of the leaf. There may be dark areas along the midrib, and areas within the leaf go brown, especially on evergreen leaves
- The plant may also look like it is short of water, even wilting
- A root sample will show blue-black roots, a typical sign of waterlogging that may be accompanied by a sour, rotting smell. Roots may rot away completely, with few remaining. Damaged roots will be blackened and the bark may peel away
- Shoots may die back due to a lack of moisture (the roots cannot supply water to the leaves) and bark peels off the shoots easily
- Herbaceous plants may fail to sprout in spring, or leaves may open and then die
- Plants may be stunted, or even die
- Some plants suffer from a condition called oedema…which, similar to humans, is the same name for a condition characterized by an excess of watery fluid collecting in the cavities or tissues of the body…or in this case, a plant’s body
Some of the symptoms are easily confused with water stress (too little water). But in fact, a waterlogged plant actually is water stressed. This is because the roots are drowning and cannot absorb any water or nutrients to move around the plant.
Cause
Excess water causes problems for plants in a number of ways;
- Water-logging limits oxygen supply to the roots and prevents carbon dioxide from diffusing away.
- Root function is reduced or stops and the roots start to die off, allowing the invasion of rots and decay organisms. This has a subsequent effect on the visible parts of the plant, as the leaves and stems are unable to obtain enough water and nutrients
- In cold, winter soils, roots respire little, so water-logging is much less damaging than during warm seasons, when roots respire freely and demand more oxygen. Few plants can survive summer water-logging, unless they have special roots adapted to such conditions. Willows and marginal aquatic plants such as flag irises are examples of these
- Waterlogged soils may be compacted or have a naturally dense texture lacking drainage channels. This means that the soil remains wet after rain
- Some soils are more liable to water-logging than others
Control
Short Term
- After flooding, Serpico washes down hard surfaces and collects up debris to prevent storm drains from blocking, soil surfaces from being covered, and avoiding any pollutants or contaminants from lingering in gardens
- Do not walk on the grounds! Keep off the soil until it is workable, to avoid compacting it and worsening the conditions
- Remove damaged shoots from affected plants
- Serpico Landscaping’s teams recommend we apply a balanced fertilizer in the spring, mulching over the root area after application
- Foliar feeds (spraying plant nutrients directly onto leaves) during the growing season may help improve leaf color, and encourage new root growth
- We water thoroughly in dry spells after a water-logged period, as plants will be more susceptible to drought stress
Long Term
- Serpico Landscaping can inspect for any needed improvements to soil structure and drainage through cultivation
- Consider planting trees on a slight mound
- Choose permeable surfaces when laying drives, paths and patios to allow rain to soak in
- If there is somewhere for water to go, drainage can be installed. Or, where appropriate, it may be worth digging out a ditch or seasonal pond at the lowest part of the garden to catch surplus water and let it soak in slowly
Northern California’s recent available irrigation water conversion — from five-year drought to a renewed water supply — has been almost overnight due to increased snowpack levels and multiple *atmospheric river* rainstorms. Now, Serpico Landscaping can help address any plant water-logging or issues after flooding on properties…as we continue to adapt to changing precipitation here in the SF Bay Area.
