Bring your garden back to life after the flood

Bernice Shepherd

For many of us, getting into the garden is a healing and grounding activity, a balm for the soul. 

But after devastating floods and relentless wet weather, what was once a beautiful sanctuary or productive food garden has become a muddy, stinky quagmire, no good for growing anything.

But according to local environmental scientist and soil analyst, Ian Thomas, your soil can be restored. 

Ian’s passion is growing delicious, quality food and he runs The Gourmet Garden School, helping gardeners to boost soil health. 

In the weeks following the flood, he generously offered a free online series to help flood affected communities recover their soil. 

The good news is that soil can be repaired very effectively using natural methods – and much quicker than you might think.

Here are some of the easiest things you can do to help return health and balance to your garden after flood or a soggy season.

Can I eat crops that have been affected by a flood?

We know that flood mud can be toxic. 

Raw sewage and heavy metals can wash in on floodwaters – so don’t eat any produce from the vegie patch for at least 8 weeks after flooding – it is best to discard anything that was growing there at the time.

Root crops especially will be polluted and should be pulled out and composted.

Leafy greens are extremely effective at sucking up contaminants and storing them in the leaf tissue – they should therefore also not be eaten but pulled up and composted.

Discard fruit that has been flooded – but fruit trees that survive the flood will produce fruit that should be perfectly safe to eat.

How do I remove contaminants?

Biological pathogens such as bacteria, fungi and viruses do not pose a long-term problem – they thrive in wet, deoxygenated, nutrient-rich conditions and will die off or go dormant once everything dries out. 

In the meantime, reduce exposure by wearing gloves, a facemask and covering cuts or wounds.  

Industrial pollution is of greater concern as these contaminants can remain in soil for decades while leaching into the groundwater. 

Leafy plants that are adept at drawing up and removing toxins from the ground can accumulate heavy metals such as poisonous arsenic. 

This is known as phytoremediation: phyto = plant, remediation = remediation.

If you believe your soil has been contaminated by industrial wastes, sow green manures for at least two cycles before planting any food crops. 

The leaves of the green manure will accumulate the toxins, effectively removing them from the soil once chopped and put in the compost. 

But this compost is best used on lawns or around non-fruit trees because the heavy metals will not go away, just be relocated. 

These plants are excellent phytoremediators when used as green manure: sunflowers, mustard and brassicas, corn and maize, broad bean, radish, lettuce, sorghum, barley and oats.                                              

If you suspect your soil may be contaminated, it may be worth sending a sample to a soil testing laboratory (some are listed at the bottom).

Composting contaminated plants

Of course, when you compost contaminated leaf material your compost will contain those contaminants, so use it only around ornamental plants you will not be eating and in areas where you will not be growing food crops. 

If you put this waste into the council green bin it is just transferring the problem elsewhere and into the environment, rather than containing it where it originated. 

The issue of environmental contaminants such as industrial waste getting into floodwater in the first place is a whole other matter – but if we want to see less pollution in the world, a good place to start is being responsible for our own.

What happens when soil gets waterlogged?

Good, healthy soil is chock full of microscopic organisms such as bacteria, viruses, fungi and nematodes. 

A teaspoonful contains thousands and even millions of organisms, known as the microbial community.

Aerobic (air breathing) organisms are essential to healthy soil. These are the organisms that create soil and provide the complex chemical conditions necessary for your plants to thrive.

Without these essential organisms, soil is dead and cannot sustain life for long.

When soil gets full of water for any length of time it becomes depleted of oxygen. Aerobic organisms in the soil die and the anaerobic ones (that do not need oxygen) take over. 

An excess of anaerobic bacteria creates unpleasant smells, which is why soil that is consistently sodden can develop a foul smell.

Soil Biology Diagram – credit Georgie Moon with permission from The Gourmet Garden School

How can I encourage beneficial microbes?

Oxygen: A healthy microbial community needs oxygen – so aerate your soil by forking it, applying gypsum or sand that will break it up, and applying organic matter. 

Most soil microorganisms need organic matter to chomp on and it is this broken down matter that creates wonderful rich soil.

Food: Bacteria like a high nitrogen environment – lots of green material, a bit of blood and bone, urine or fishmeal. 

Fungi like the opposite – high carbon and low nitrogen – so add straw or woodchip to encourage healthy mycelia (the white strands of fungi under the soil).

Our little aerobic soil buddies (bacteria) love sugar. Try adding a teaspoonful of molasses or something sugary to your watering can to encourage them. Avoid honey as it has strong anti-bacterial properties and you do not want to kill them off.

Inoculate your soil: Even a teaspoonful of good, healthy soil or compost (from a non-flooded friend) added to your garden will contain many of the good microbes you need, and these will multiply and spread through your garden.

You can also inoculate your soil with compost tea. Add water to a bucket of chopped up uncontaminated plants and let it sit for no more than one or two days – until bubbles form. 

You could also aerate your tea with a ‘whisk’ attachment on a drill – like a giant stick mixer. 

Add a good splash of the ‘tea’ to your watering can.

Of course, there is a lot more to creating rich, healthy soil – most backyard soils leave something to be desired even without waterlogging. 

Where soils have suffered in the recent weather events, there is an opportunity to learn how to boost and enrich them, giving a more fertile ground ready for spring. 

And once you are able to get out into your garden again, planning, renewing and getting your hands dirty – it will help restore you.

If you want to learn more about improving your soil, visit Ian’s YouTube channel

Or join the Facebook Group

Soil Analysis: The Gourmet Garden

Soil Testing: EAL Laboratory for contaminant testing: Phone 6620 3678

Vegesafe takes some weeks to come back so maybe search for labs online.

Gardens are waterlooged after all the rain.
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