In the aftermath of a flood, the health of the garden probably doesn’t rank highly in most people’s priority list, however a few timely actions will vastly improve your garden’s prospects for recovery. Whilst the initial impact of flooding on the landscape is readily apparent - with broken branches, defoliated plants, soil loss, debris and sediment everywhere – the most significant damage is not so obvious and may take a while to become apparent.
Even short-term flooding has the potential to cause significant damage to the soil and plant root systems. When a soil becomes flooded, oxygen – essential for root respiration and soil microbes – is quickly eliminated from the soil. As little as 24 hours of complete immersion can compromise the health of the roots as well as the plants themselves. Although some plants are more tolerant of waterlogged conditions than others, most landscape plants can survive being submerged for about a week or so. Even so, the consequent root damage can make them susceptible to a range of pests and diseases and decrease their tolerance to other environmental stresses – including high temperatures and lack of water over the coming months. It is also important to note that a heavy accumulation of sediment or soil can be as damaging as a layer of standing water, denying the roots of precious oxygen.
The first step in post-flood garden recovery is to allow the soil to drain naturally. Working with wet soil may cause long-term damage to soil structure through compaction. This is a particular problem with heavier soils which tend to compact to a greater degree. Heavy clay soils will take several days to dry out to the point where gardening can start. Before beginning any work, ensure you’re wearing gloves, strong footwear and appropriate clothing to protect yourself from potentially contaminated soil and sharp debris. If plant foliage and stems are heavily silted or covered in debris it is advisable to hose them off gently, taking care not to add too much to the already sodden conditions. Mud or silt can also be gently scraped off plants. Silt covered leaves will affect the plant’s ability to function effectively.
Although dependent on a range of factors, lawns are generally able to survive up to four days of submersion. Floods can however create conditions that result in several challenges for your lawn. It is advisable to minimise foot traffic on waterlogged soils because they are very prone to compaction. As a first step in recovering your lawn, carefully remove any debris (glass, metal, stones etc.) that may have accumulated on the lawn, especially any safety hazards. Ensure you wear strong gloves, sturdy footwear and long-sleeves to avoid cuts and scratches and soil-borne diseases such as tetanus.
The other key consideration is the impact of accumulated silt, soil sediment and organic debris. In many instances this accumulated material should be fairly minimal and is easily dealt with, but larger deposits are a bigger issue. For lawns with less than 20mm of sediment, spread evenly across the grass surface with a steel rake, providing the lawn with a useful layer of topdressing. This layer can easily crust over and prevent air movement, so it is essential to keep it loose and well-aerated through regular raking. Avoid dragging the rake too deeply as this can damage the underlying turf. Lawns that have greater than 20mm of sediment have worse prospects for recovery, but if excess silt is removed quickly and the surface crusting is kept well-aerated it may have a fighting chance. If the lawn does not show signs of regeneration within a few weeks, then it is time to consider re-establishing the lawn. Before doing so, it is critical that the dead layer of lawn below be thoroughly broken up and incorporated into the surrounding soil, otherwise it will act as a barrier to new root growth and limit air and water movement. Establishing a new lawn quickly will help guard against soil loss in the next downpour. Read our detailed information on establishing new lawns from seed or turf.
Lawns will also greatly benefit from a feed following a flood, helping to replace any lost nutrients and aiding in their rapid regeneration. Yates Dynamic Lifter Concentrated Lawn Food is an organic based lawn fertiliser that contains fast acting nutrients to encourage deep green lawn growth as well as rich organic matter to promote soil health.
The stress and damage caused by flooding may also predispose your lawn to disease. Consult the Yates lawn problem page which has pictures of various lawn diseases to help you identify the potential problems. You may also find that weeds, including many from seeds transported in the floods, may establish themselves in your lawn. However, it is best to delay controlling weeds until the lawn is not stressed and it has begun to regrow. A range of common broadleaf weeds can be controlled with selective herbicides such as hose-on Yates Weed’n’Feed or Yates BuffaloPRO Weed’n’Feed, which is safe to use on buffalo lawns.
Flood Affected Fruit & Vegetables
Edible produce in your garden that has come in contact with flood water may be contaminated and certain foods will have to be thoroughly disinfected or discarded. “Vegetable gardens can take a month to become suitable for harvest after flood or sewage discharge. Discard all leafy green produce or damaged vine or dropped tree fruits. After 1 month, wash other vegetables then sanitise in a weak bleach solution of 1 tablespoons bleach to 2 litres of water. Then rinse in drinking-quality water, peel and use. Monitor announcements and consult local authorities after other sorts of contamination. If in doubt, throw it out.” Source - https://foodsafety.asn.au/food-safety-in-emergencies/.
To prevent mosquitoes breeding in your yard it’s important to remove all sources of standing water from your garden. Empty out water features, pot saucers, waterlogged rubbish and other receptacles and try to promote water to drain from your yard. Mosquitoes also rest and hide on plant foliage. Mosquito numbers can be reduced by spraying Yates Home Pest Long Term Control Barrier Spray over leaves and the leaf litter below plants. This spray kills mosquitoes and creates a mosquito barrier on foliage for up to 14 weeks.