What to do for flooded gardens is, unfortunately, a question more people need to ask.  It seems that our climate is making extreme rainfall and subsequent flooding more likely in some parts of the country.  For gardeners this is a heart-breaking experience on top of the damage to homes and other possessions, but for those whose gardens have been flooded, some caution is needed.  We summarise here advice from research institutions specializing in agriculture, horticulture and arboriculture on how to manage flood-affected gardens.

How Floods Affect Gardens

Floods can kill plants or severely damage them by:

  • Erosion of soil so that roots are exposed. This makes trees more susceptible to uprooting in  subsequent winds.
  • Water logging, silt deposition or compaction removing oxygen from soil spaces around plant roots. This can also destroy microbial life that is essential in soil to provide nutrients for plant growth
  • Making roots more susceptible to root-rot organisms
  • Contamination from run-off from roads, farms and industry, sewage and other chemicals from transport vehicles and household products. These may include heavy metals such as cadmium, arsenic and lead, pesticides and other hazardous chemicals from industry such as oils
  • Buildup in soil of decomposition products such as ethanol, carbon dioxide and methane
  • Prevention of photosynthesis by water or silt coverage of leaves
  • Removal of bark from tree or shrub trunks from impact of debris in rapidly flowing water
  • Insect infestation resulting from damage to trunks may further weaken trees and shrubs.

On the other hand, river plains that are affected by floods and properly managed after the flood are among the most fertile areas for many crops.  Here the emphasis must be on appropriate management!

General Garden Recovery from Flood

Initially do nothing!  Difficult as that may be, trying to remedy garden damage before soil has dried out sufficiently can do even more damage.


  1. walk or dig since these actions cause more compaction and disturbance of soil structure. Wait until water has drained and dried enough so that soil is firm enough to stand on without sinking in.
  2. prune plants whose leaves are wilting as soon as waters have subsided. You may be surprised as some slowly recover.
  3. add fertilizer since stressed plants will not take it up and subsequent rains my wash it away.

What you can do:

  1. Allow sufficient time to assess tree and shrub damage. They may lose leaves or branches may be broken, but remove only obviously dead branches.
  2. When walking on soil after flood waters have subsided, be aware of risks of standing on or touching debris such as broken glass or nails which could cause injury.
  3. Wear gloves and closed shoes which should be removed before entering any dwelling to avoid spreading contamination. And wash hands thoroughly after removing gloves
  4. If lower leaves of non-produce plants that covered in silt, try hosing it off – maybe even using a pressure hose. Although adding more water to the garden sounds peculiar, leaving silt on leaves will inhibit block sunlight, inhibiting photosynthesis which plants need to perform in order to survive.
  5. It may be useful to add fungicide since wet warm conditions after floods can stimulate fungal growth.
  6. Add commercially available soil microbes and organic matter to the soil surface. If you use fungicide, wait a week before adding microbe preparation. They will help the natural soil biota which are so necessary to breakdown organic sources of nutrients and for preventing both human and plant disease.

Can I Eat Produce from a Flooded Garden?

Since flood waters carry contamination of various sorts, including toxic chemicals and pathogenic bacteria (e.g. E. coli, Salmonella) or parasites, which affect food safety, you will, unfortunately, need to discard some produce or delay planting again.  Appropriate action depends on the type of produce and the degree of exposure to the waters.

Fruit or vegetables that have come into DIRECT contact with flood waters

These should be discarded if they have been submerged or been splashed by the waters.  Some research organisations suggest that if the produce has only been splashed, you could wait 72 hours before harvesting, then thoroughly clean and cook it before eating it.

However, some produce that has been splashed is particularly risky e.g. those with soft surfaces e.g. leafy greens, berries, tomatoes, eggplants, peppers or melons, and should not be consumed.

It is wisest to discard root crops like potatoes and carrots.  Crops like rhubarb or asparagus should be dealt with in the same way.  However, the University of Wisconsin-Madison and West Virginia University  suggest that root crops may be salvaged by cleaning first with drinking water, then bleach and rinsed again with water ( see those website for details).

Whether submerged or only splashed, no produce should be eaten raw.

No produce that has been exposed should be preserved by any method because preservation processes are not guaranteed to remove or destroy contamination.

When handling any produce from a flooded garden make sure to prevent cross-contamination by washing hands thoroughly with soap for 30 seconds between dealing with different types of fruit or vegetables.

Produce that Floodwaters Have Not Touched

There are slightly different opinions about how long you should wait to eat produce that matures after flood waters have receded and were never in direct contact with the waters.  Estimates of between 90 – 120 days are if the produce is peeled and cooked.  Make sure that it is completely intact with no cracks, holes or bruises – such produce should be discarded.

Planting Next Season’s Edibles

It is advised not to sow or plant after the flood until at least 2 months have elapsed.  For fruiting plants like tomatoes, wait 60 days, but for root crops like radishes wait at least 100 days.  During this time adding organic matter to the soil would be useful.

This might be a good time to install raised garden beds to reduce the chance of edibles being affected in subsequent floods.