Garden Doctor > Dealing with Flooding

Many gardens have been affected by extreme weather this summer. Plants growing in soil that has been waterlogged or flooded for any length of time will have been compromised. Ground that has flooded and then drained after a few days will recover as it dries out, but soil that remains waterlogged will ultimately cause damage to plants and gardens.

Beds and borders

Plants submerged in water will be susceptible to root problems and fungal rots such as phytopthora and are unlikely to recover. Plants growing in waterlogged soil have a better chance if the soil is likely to dry out. The best solution is to dig up affected plants and replant them into containers using a quality potting compost, away from the waterlogged soil. Choose Westland John Innes Mature Plant Compost for best results.

These plants will need care and attention and may already have been damaged. When you remove the plants from the soil examine the roots and cut away any that are affected. It may also be a good idea to reduce the top-growth (stems and shoots) of the plants. Prioritise your time and deal with precious plants in the first instance.

Keep off waterlogged areas as much as possible if they are likely to drain, as trampling over the ground will compact the soil further.

If waterlogging is a recurring problem then look at the overall drainage of your garden. You could consider creating a bog garden where the garden soil is permanently waterlogged, or you could try to improve the drainage of the ground. Soil structure can be improved by digging in Horticultural Grit or copious amounts of Farmyard Manure or Premium Topsoil. Extreme conditions may require underground drains installing so take expert advice. Dig over the area as thoroughly as possible, loosening compacted soil, but try to avoid moving heavy subsoil to the surface as this may compound the problem. Initially allow weeds to grow but hoe them off before they flower and set seed. By allowing them to grow they will take water from the soil and speed the drying out process.

The soil micro-organisms and beneficial creatures may also have been affected by the floodwater. These need to be replaced. Organic matter will encourage worms and beneficial microbes to return to the soil. Speed this process by digging in your own home made garden compost that will be full of the active microbes essential for a healthy soil.

Food crops

If your vegetable patch has been swamped with floodwater it is not safe to eat the crops as they may have been contaminated with sewage. Dispose of any food crops and try and clean up the area. Be sure to protect yourself from contaminated water by wearing waterproof gloves, clothing and boots. If the vegetable garden has been waterlogged by heavy rain and not floodwater you need to allow it time to dry out. Harvest any vegetables that are still viable and wash them thoroughly before using. Consider building raised beds to accommodate your vegetables for next season.

Lawns

If the lawn has been underwater for a week or more or completely covered with flood debris then it is unlikely to recover and may need to be replaced. Silt from floodwater and any resulting debris will need to be removed because it could be contaminated. Be sure to protect yourself from contaminated water by wearing waterproof gloves, clothing and boots. If the lawn is waterlogged keep off it until it starts to dry out. Rake off the surface debris and then aerate the whole area using a hollow tine aerator. This will remove plugs of soil from the lawn, brush Sharp Sand into the resulting holes to improve drainage and then use the Lawn Repair Kit to resow any bare patches.