A third consecutive La Niña has been declared for the end of 2022 and may extend into early 2023. La Niña events typically bring heavy and widespread rains to many parts of Australia. While most plants love a good watering, persistent wet weather is not always a good thing for plants. Wet soils can lead to root rot and fungal diseases, while wet plants can be blown over in storms or damaged by heavy rain. Heavy rains also leach nutrients from the soil and can encourage weeds to grow.

While there are some plants that tolerate periodic inundation such as bottlebrush, birch trees, cannas and bog plants, most ornamental and productive plants prefer soils that drain well. Plants that are adverse to prolonged wet conditions include Mediterranean plants such as lavender, rosemary and many herbs.

Knowing that rain can be both a blessing and a curse helps you to get on top of any problems quickly and efficiently. Here are a few things to keep in mind.


Perils of wet soil

When soils get overly wet during prolonged periods of wet weather, water fills all the air spaces that naturally occur in soils. If the water takes too long to drain, roots can drown. When the heavy rain occurs after a long drought, plants that have survived the drought can suddenly drop dead as they are unable to cope with the inundation of water. Overly wet conditions can also affect potted plants.

What to do

Consider ways to improve drainage in areas that are very wet – for example, by installing more surface and sub-surface drainage, and/or creating raised garden beds. While it is raining, make temporary drains to divert run-off from wet areas. Also, check that all existing drains are clear and able to carry water away. Compacted soil where water is pooling may benefit from aeration. Avoid walking on very wet soils where possible and hold off on new plantings until the wet weather subsides.


Following a lot of rainfall, soils and lawns can become waterlogged, which can drown the roots of your plants and grasses.



Even where there’s drainage, wet soil conditions after heavy rain encourage diseases to spread through the soil (such as root rot diseases). You may notice plants wilting even though they don’t need watering, which is a sure sign of root dieback due to root rot. Wet conditions also lead to increased disease in the above-ground parts of the plant including leaves, stems, flowers and fruit.

What to do

Plants suffering from root rot or soil-borne diseases can be treated with phosphoric acid, a safe treatment sold as Yates Anti Rot. Regular liquid seaweed treatments with a product such as Amgrow Seaweed Concentrate can also help plants survive adverse conditions. Plants that can’t cope with wet conditions may benefit from being temporarily dug up and potted while the wet soil conditions are addressed. Having open, well-spaced plantings with good air circulation can help reduce problems after rain, so prune to open plants up. Also remove weeds and make sure that mulches, particularly organic mulches, haven’t built up around the main stem or trunk. Remove dead and rotting foliage from perennials and other clumping plants.

Some of the fungal issues you may notice on foliage and flowers during persistent wet weather include rust, blight, mildew (powdery and downy), black spot and sooty mould. Extended periods of humidity tend to exacerbate the problem as the air isn't able to dry the plants out quickly enough. Flower Power's resident expert recommends Amgrow 3 in 1 Insect, Fungus & Mite Control as a great ready-to-use option, or for a concentrate, try Mancozeb Plus.


Constantly-wet foliage can lead to fungal infections.



Pest numbers are also likely to increase after rain, especially snails and slugs, which are very active in wet conditions.

What to do

Be alert for signs of pests and deal with them as quickly as possible - for example, control snails around new plantings and seedlings with a safe, iron-based snail bait. Flower Power recommends Multiguard Snail & Slug Killer.


Hungry snails are particularly problematic in wet weather.



Weeds grow quickly after rain.

What to do

Keep on top of weed growth with regular manual weeding and hoeing to remove emerging weeds.


Wet weather provides the perfect conditions for weeds - including dandelions - to take off.


Nutrient loss

Persistent and heavy rains can also leach nutrients from the soil. Combined with the excessive growth that can occur after rain, plants can become nutrient deficient very quickly.

What to do

Liquid feed to top up plants and also spread pelletised fertiliser while soils are moist. For a liquid feed, Flower Power recommends Harvest, while for pellets, they recommend Supergrow Organic Fertiliser Pellets.


A gardenia showing signs of nutrient deficiency.


Waterlogged pots

Potting media in containers can become too wet during heavy rain leading to plant death or dieback. Heavy rain can also damage plants.

What to do

Check drainage holes – they may be blocked, preventing water from draining from the container – and clear blockages or re-pot into fresh, well-draining premium potting mix. Flower Power recommends Supersoil Professional Potting Mix. Also improve drainage issues by elevating pots onto pot feet or bricks. When rain is persistent and plants are getting damaged, move them into a sheltered spot until the rain stops. Prune away damaged growth.


Heavy rain can cause damage to plants, including breakage.



Heavy rains can wash away or disturb mulches in gardens.

What to do

A thin layer of mulch helps to protect soils from heavy rains, reduces weed growth that may be triggered by moist conditions and can stop disease organisms being splashed from soils onto above-ground growth. After bouts of heavy rain, check mulches – raking over them or renewing them as necessary. Also check that mulches are not blocking drains or spread over pathways. Inorganic mulches such as gravel may work better around plants that need good drainage such as Mediterranean plants.


Always check your mulches after heavy rain to ensure they're still in place. If not, rake over them or top them up to provide a weed suppressing barrier.