What to do for Waterlogged or Flooded Gardens

By Marie Iannotti, About.com Guide

We have less control over our plants during prolonged periods of rain or flooding, than during drought. Unless they are in moveable containers, there is little we can do except wait for the weather to change. Then it is time to take stock of how your garden held up.

If your soil is waterlogged, chances are good your plants are showing signs of stress - or soon will be. Waterlogged and flooded soil has insufficient amounts of oxygen in it, for the plant roots to take up and release water or release excess carbon dioxide. Plants may paradoxically look like they are wilting, but it is not because of too little water, it is because they can no longer access the available water. This leads to root rot and death. While we may not be able to prevent flooding, we should at least be on the alert for signs our plants are struggling. Start by watching for these signals.

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Symptoms of Water Damaged Plants

Symptoms of water damage can look just like many other plant problems. Symptoms are generally first apparent on the leaves, although trees and shrubs may not exhibit symptoms for a year or more. Signs you plants have been damaged by waterlogged soil include:

• Stunting
• Yellowing leaves
• Twisting leaves
• Dropping leaves
• Soft, spongy areas at the base of the leaf
• Wilting despite plenty of water
• Roots turning dark, often with a rotting odor.
• Lack of flowers or fruits
• Shoot dieback

Several factors determine how much damage is done to plants by flooding, including how long the soil is waterlogged, whether it is fresh or salt water, the time of year and the type and age of the plant. Flooding during warm weather is more damaging to plants, because they are actively respiring and need more oxygen than during cold weather.

A short-term period of soggy soil probably won't cause much damage. It is prolonged periods of flooded soil that cause problems. Although some plants, like willows, bald cypress, flag iris and other bog plants, can adapt to long periods of flood waters, most plants cannot; some can handle as little as a few days.

What to do for Waterlogged Plants

Unfortunately, once the soil is flooded, there is not much you can do but be patient. Just because a plant shows signs of distress doesn't mean it won't eventually recover. In the meantime:

Don't walk on waterlogged soil. You will just compact it and cause more damage to distressed roots.

If the plants were underwater, clean them off with a hose, to remove and sludge and other residue.

Keep an eye out for diseases that will take advantage of stressed plants. Fungal disease, in particular, favor damp weather.

You can purchase a relatively inexpensive soil moisture meter at most hardware stores. A meter will tell you the percentage of water remaining in your soil. If you still have mud, you won't need a meter to tell you the soil is waterlogged. But if you are wondering if it is dry enough for the roots to get the necessary oxygen, a meter will tell you when the soil has reached that level (usually between 40 - 70%).

For Flooded Container Plants:

• If the waterlogged plant is in a container and you can't move the container somewhere sheltered, take the plants out of the container and let them sit and drain on newspaper or cardboard overnight. Once they have dried enough to see the roots, prune off any that feel slimy, before repotting in dry soil.
• Potted plants that have been contaminated with sludge are best disposed off.
• Empty and clean pots, water trays and saucers, then wash them in warm soapy water.
• Soil in flooded containers will have lost most of its nutrients and will need a new dose of fertilizer. Use a slow release organic fertilizer, to release the nutrients over time, as the plants recover.

If you are gardening in a flood prone area, consider trying one or more of these options:

1. Raised beds - They will still be susceptible to flooding, but will drain and warm faster.
2. Permeable hardscaping - These will allow more drainage on driveways and patios, limiting runoff.
3. Green roofs and rain gardens - these slow runoff and filter impurities.
4. Dig a pond - divert the run off to a holding area, even if it won't be full all year.
5. Choose water tolerant plants - Why keep fighting it?

Sources:
Royal Horticultural Society
University of Illinois Extension

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