Do you have waterlogged pot plants? In eastern Australia and particularly Queensland, a large number of homeowners suffer inundation by flood waters as a result of extreme weather events every year. You may live in a heavy rainfall area and you may have the same problem. Prolonged heavy rainfall and flooding can cause havoc for us in our gardens.
So how do you clean up plants that may have been contaminated by flood waters? How do you revive plants that have been affected by heavy rainfall? Or soil that is just badly waterlogged?
I’ve had to have my own strategies for coping with subtropical weather events so here are some steps to follow for pot plants that have been completely inundated by flood water:
- Firstly, hose off the plant foliage to remove any sludge or chemical residues – use higher pressure for strong shrubs and potted trees and lower water pressure for delicate plants.
- If the pot has accumulated sludge from the flood waters on top of the soil or mulch, remove it (make sure you use gloves for protection in case of bacteria, chemicals or toxin residues) and bag this up to go in the bin. You don’t want this contaminating other parts of your garden or coming in contact with humans or animals.
- Empty any pot saucers to prevent mosquitoes breeding.
- Next, scrub the outside of the pot and rim with warm soapy water. Use a safe biodegradable or environmentally friendly soap not one with chemicals because if the pot surface is porous, it will absorb these and they may end up in the soil.
- It is likely the beneficial microorganisms and soil life that were living in your pot and keeping your plant healthy have drowned or at best case, their numbers have greatly reduced. If this is the case, the potting mix or soil may smell ‘sour’ or anaerobic. Oxygen normally fills the gaps in between the soil crumb structure and all organisms and plants need air to live. When plant roots start to decay, you may notice this unpleasant smell.
Other clues there is something wrong with your soil or potting mix are:
- your plants are wilting or looking decidedly ‘unwell’ all of a sudden
- your plants are being attacked by pests
- worms are coming up to the surface in great numbers (they are trying to save themselves from drowning!) and
- sometimes you might notice a scum or residue on the surface of the soil.
The good news is … you have a number of options to restore soil and plant health:
- If you don’t want to re-pot the plant and the soil is still smelly, then to sweeten it you can add a sprinkling of garden or agricultural lime which should help remove the odour. If however, you have a plant that prefers an acidic soil, then avoid this treatment.
- If you are prepared to re-pot your plants, then you can re-use some of the potting mix but add some other ‘ingredients’ to build up the health and restore aeration.
Make sure you use gloves and a mask when mixing up the soil and add equal parts of fresh compost, worm castings and if possible, vermiculite to retain minerals and aerate the potting mix. Grade 3 Vermiculite (a puffed natural mineral called mica) available at garden centres and nurseries is a good size and helps aerate plant roots. Alternatively use a coarse washed river sand available at landscapers for very low cost.
- Remove any dead or dying shoots or foliage at this time with clean secateurs. Pay attention to tool hygiene and ensure you wash your tools in warm soapy water if they have been used on sick plants.
- If you are not re-potting, you can add beneficial microorganisms back into the soil by gently forking in some fresh compost and/or worm castings into the top layer of the pot without disturbing the roots of the plant. Then ‘feed’ them with a drink of diluted molasses and seaweed or kelp. Molasses is a thick black liquid that is basically a simple sugar that beneficial soil bacteria go crazy over at their ‘dinner table.’ It is usually sold cheaply at health food and garden produce stores and is a great investment in soil and plant health. A capful in a watering can is all that is needed. Follow the directions for the dilution of the seaweed fertiliser. Once the microbes have some food, they will have enough energy to start to multiply and get to work in your pot, restoring the pH balance and health. Repeat this treatment every 2 weeks until the plant recovers and soil health is restored.
- Use a moisture meter to measure how much water is still in your soil.
These are usually available at garden centres and hardware stores for around $10 but are a valuable diagnostic tool for you in the garden. If the soil moisture measures above 80%, it is still too wet so let it dry out before adding any more water. The ideal moisture level is between 40% and 70%, which allows some oxygen to stay in the soil.
- Finally, check the drainage holes at the base of the pot.
Make sure these are free of roots or blockages so water can drain away freely. If your pots get waterlogged frequently, consider drilling more holes in the pot or transplanting into a more suitable container. Adding gravel to the pot saucer will also help drainage or put the pot up on feet or a portable trolley to enable water to drain freely.
A waterlogged soil is not a healthy environment for plants to live – much like we would not be comfortable living under water all the time. We need to come up for air and the plant roots need oxygen too. Saturated soils with poor drainage can quickly become anaerobic, making the plant susceptible to diseases like root rot. When plant roots sit in excess water for too long, they start to rot or decay. As the roots deteriorate, they can’t take up water, so the plant wilts. Resist the urge to water your plant – it can actually make things worse! Waterlogging and compaction can create ideal conditions for diseases such as phytopthora and other fungal attacks.
- If the pot or container feels heavy and the plant is still wilting, the excess water may not be getting away fast enough. If you have already drilled enough holes, you may need to actually remove your plant from the pot to save it. Spread out a number of sheets of newspaper in a tray. Lay the pot on its side and gently slide out the plant’s root ball.
Allow the root ball to dry on the newspapers for about 12 hours, then using clean sharp scissors, trim off any dark-coloured (brown rather than white) or slimy roots. When you are finished, re-pot the plant in a clean container with some fresh potting mix as already outlined.
- Whilst most books and websites on container gardening recommend the addition of coarse material such gravel, sand, pebbles, pottery shards or polystyrene pieces to the bottom of pots to improve drainage, scientific research studies have consistently demonstrated quite the opposite is true. According to one scientist, Dr Chalker-Scott, Extension Horticulturalist and Associate Professor at the Washington State University:
“Nearly 100 years ago, soil scientists demonstrated that water does not move easily from layers of finer textured materials to layers of more coarse textured. Since then similar studies have produced the same results. The coarser the underlying material, the more difficult it is for the water to move across the interface. Gravitational water will not move from a fine soil texture into a coarser material until the finer soil is saturated. Since the stated goal for using coarse material in the bottoms of containers is to “keep soil from getting water logged,” it is ironic that adding this material will induce the very state it is intended to prevent.”
- Pot plants that have been inundated with water will also have likely leached out much of the plant food or fertiliser that was in the pot previously. You will need to replace this food source with some more organic fertiliser to ensure your plant has the energy it needs to regain its health. If you notice discoloured or yellowing leaves this is often a sign your plant is crying out to be fed because it is missing essential minerals in its ‘diet!’
Choose a slow release, powdered or pelleted organic fertiliser and if the plant patient is really suffering, a foliar spray on both the top and underside of the leaves early in the morning with kelp/seaweed will give it a quick ‘pick me up.’ Use a spray bottle for this – see Frugal Gardening: 5 Thrifty Recycling Ideas on how to get one for free.
- To minimise future waterlogging perhaps from heavy rains and storms, consider moving your pots to a more protected position, such as under an eave on a verandah or balcony if possible.
- Add a layer of mulch to the top of your pots which also stops valuable potting mix from splashing out of the pot and provides a buffer between the soil and the water.
Work with nature!
If you live in a high rainfall area and your plants are constantly getting swamped, consider working with nature – not fighting it! Start again with water loving plants that thrive in wet conditions – you’ll have less work to do in the garden as a result and have more success.
If you live in an area that has been flood, storm or rain affected but your garden escaped, now may be the time to take a few cuttings and share them around with neighbours, schools or community gardens that suffered damage. No doubt they will be warmly appreciated. Starting over from scratch can be very disheartening – but when seeds are replanted and others offer help, the task doesn’t seem as daunting. Gardens have an amazing capacity to heal the spirit – they provide a haven, hope and watching nature regrow and renew itself, often helps humans do the same. It is well summed up in this quote:
“The greatest gift of the garden is the restoration of the five senses.” – Hanna Rion
Has your garden suffered damage? Do you have a problem you need help with? Share your thoughts here.
© Copyright Anne Gibson, The Micro Gardener 2010-2013 – http://www.themicrogardener.com. All rights reserved.