Water Inundation and Your Garden

How to Save Your Garden After Water Inundation

Due to the subtropical nature of Southeast Queensland, it’s likely that at some point your garden will be inundated with water. We hope that the water is only from large amounts of rain, but it could unfortunately be from a flood or even a burst water pipe. If water inundation does happen in your garden, follow our recommendations below to help get it back on track. 

1. General Clean Up

   Collect fallen branches and rake up leaves and twigs from grass areas. Clean mulch that has washed up against tree trunks.

2. Plant Clean Up

   An important step in aiding the recovery of treasured garden plants is to remove any mud and silt caked thickly onto the stems of branches or built up over the roots. It is important to do this as quickly as possible as it is easier to hose off while it is still wet. Once dried the task becomes much more difficult. The soil in the gardens that has become completely submerged quickly becomes anaerobic and it is this lack of oxygen that cause plant roots to die.

3. Specific Plants to Closely Monitor

   Grevilleas, wattles and most banksias cope poorly with prolonged inundation. Pawpaws, passionfruit, citrus, frangipani and many fast-growing climbing vines are also prone to root rot.
   Sudden wilting and tip dieback are often the first signs of serious problems. Expect to see increased bud drop on camellias and fruit drop and split fruit on productive trees over the coming season.
   Soft-wooded trees like poinciana and jacaranda are prone to failure. Keep a careful watch on then in the coming months as it can be sometimes before mature trees fall victim to decay.

4. Cuttings & Pruning

   Grab cuttings of fast-growing plants like salvias, dracaena cordylines and tropical species. Cut cannas, heliconias and ornamental gingers to ground level and allow them to reshoot. Large palms that have been blown over by the wind can often be pulled upright and saved. Even those toppled by fast flowing water are worth salvage attempts.

5. Vegetables & Annuals

   Vege crops and flowing annuals pummeled by constant rainfall are best removed and composted. It is likely they will soon turn to mush if they have not already done so.

6. Rejuvenate the Soil

   Aerate the soil using a garden fork and allow time for the soil to breathe before attempting any replanting. Seaweed is a great tonic to repair damaged root systems and ward off fungal root disease. It is also a great tonic to repair damage to soil structure done by seawater inundation and swimming pool overflow. Apply each week until plants show signs of recovery. We also recommend adding a compost or soil improver to the garden soil, to add back any nutrients that might have been washed away. 

7. Useful Liquids

   Liquid silica and potassium are effective in both combating root disease and fungal problems affecting plant foliage. Beneficial trichonderma fungi (used by professional arborists as liquids and pastes) and biodynamic silica sprays are more difficult to obtain but may also be used.

Original article by Annette McFarlane, published as “Starting again after getting submerged” in Courier Mail, 3 February 2013, pg. 56.