Feature

After the floods: Repairing your lawn and garden

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After the floods

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 manifest itself.

Even short-term flooding has the potential to cause significant damage to the soil and the root systems within. 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 that rely upon them. 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 resultant 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 water deficit. 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.

Garden Recovery

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 work can commence. If plant foliage is 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. Silted leaves will affect the plant’s ability to function effectively.

Floods can also take their toll on soil nutrient levels. Erosion, leaching and disruption to soil microbes can decrease the level and availability of various soil nutrients, particularly nitrogen. Replace lost soil from garden beds with compost-rich soil and a layer of mulch. This will not only cover up any exposed plant roots but also create a more stable environment for them should the weather become warm and dry. You do not want your plants to be faced with one extreme after another. Plants should be given a light fertilisation to help replace lost nutrients and encourage regrowth. Yates Dynamic Lifter, Blood & Bone, Thrive, Aquasol or Multi-Nutrient Plant Food are all suitable fertilisers.

Waterlogged soils can also become acidic. If a pH test shows this to be a problem then both lawn and garden will benefit from the application of lime (rates will depend on starting pH). To repair the damage done to soil microorganisms and improve plant survival and recovery, apply a seaweed formulation such as Yates Nature’s Way Seaweed Booster. Apply to the foliage and root zone at 2-4 week intervals.

Monitor all flood-affected plants thoroughly for signs of stress in the weeks following a flood. Above-ground symptoms of stressed plants may include leaf yellowing, drooping foliage, leaf drop and branch die-back. The longer your garden has been wet, the more likely it is that they will become infected with bacterial and fungal diseases – including various root and collar rots which are often able to gain a foothold following flooded conditions. A suitable fungicide may need to be applied once a diagnosis has been made. The Yates Garden Problem Solver may help you with the diagnosis. Yates Anti Rot is a low toxic preventative fungicide used to control a range of root and collar rots and works by boosting the plant’s own defence mechanisms. For those plants which are showing signs of die-back, don’t be too hasty in removing their limbs. Determine whether the branches are dead – live stems and buds will reveal green tissue when the surface is scratched. Prune all dead, broken or diseased branches.

Lawn Recovery

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 a number of 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 and long-sleeves to avoid cuts and scratches and soil-borne diseases such as tetanus.

Flood afftected area

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 disturbance with a steel rake. 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 tilled 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. Here is some detailed information on establishing new lawns (from seed or turf).

Lawns will also greatly benefit from the addition of nutrients following a flood, helping to replace any lost nutrients and aiding in their rapid regeneration. Suitable fertilisers include Dynamic Lifter and Yates Lawn Master. Calculate lawn size and apply fertiliser evenly at around half the recommended rate (more suitable for stressed lawns). In addition, the lawn will benefit from the addition of a quality seaweed formulation, such as Yates Nature’s Way Seaweed Booster. Apply to lawns at 2-4 week intervals to stimulate root growth and boost overall lawn health.

The stress and damage caused by flooding may also predispose your lawn to disease. Symptoms should be carefully noted (or preferably photographed) and discussed with a local horticulturist at your local nursery who can recommend appropriate treatment options. You may also find that weeds, including many from seeds transported in the floods, may establish themselves in your lawn. You should be in no great hurry to control these, particularly whilst your lawn is still stressed. The weeds will at least provide temporary cover to the soil and even help in drying the soil out. A range of weeds can be controlled with selective herbicides such as Yates Bindii & Clover Weeder Concentrate or Buffalo Pro Hose-on Weedkiller (read labels first). The Yates Problem solver is a useful tool for identifying and controlling weeds.

Flood-affected Fruit and 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. The NSW Food Authority indicates that: “Vegetable gardens can take a month to become suitable after flood or sewage discharge. Discard all leafy green produce. 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.” (Source)

Mosquitoes

To prevent mosquitoes breeding in your yard it important to remove all sources of standing water from your garden. Empty out water features, pot plant bases, palm fronds, waterlogged rubbish and other receptacles and try to facilitate drainage of standing water from your yard.


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