Wet Feet Kills!
Wet feet is the number one plant killer. Almost 70% of all plant deaths in Melbourne, within the first few months after planting, are caused by wet feet.
Chris & Marie’s Plant Farms have a garden inspection service which visits and assists customers experiencing difficulties with establishing our plants. We have visited hundreds of customers and have discovered that 7 out of every 10 problems are caused by wet feet.
WHAT IS WET FEET?
A lack of oxygen in the soil around the root zone of plants occurs when the soil is saturated with water for more than a day. Organic matter starts to decompose and uses up all of the available oxygen thus the plants die due to lack of oxygen being available for uptake through their roots. Wet feet can be detected by saturated soil containing lots of organic matter, a septic or anaerobic (aka stinky-poo) smell and discoloured or dying plant roots.
IN WHAT SITUATIONS IS WET FEET COMMONLY FOUND?
Where plants are planted in heavy clay with a lack of air porosity. Particularly where there is a lack of topsoil and the planting hole is dug into very dense clay sub soil.
In courtyard areas, around driveways, concrete pathways or retaining walls many garden beds have no provision for water to drain away from beneath the ground. Most shrubs and flowers require a well-drained root zone to a depth of 12″ and small ornamental trees require a well-drained root zone to a depth of 18″-24″. Wet feet is likely to occur where garden beds have been constructed and surrounded by hard landscaping with no provision for subterranean drainage of the root zone.
Planting in 3 way, 4 way or Organic Soil Mixes
Many garden soil mixes are made from a mixture of very fine sand and rapidly decomposing organic matter. Within a few weeks these soils become waterlogged and the organic matter decomposes, causing the soil to compact into a very heavy wet anaerobic soil. These soils can cause wet feet even when the garden beds are otherwise well drained.
Excessive Watering of Garden Beds
Garden beds that have automatic watering systems and garden beds that are down slope from automatic watering systems are often watered too frequently, particularly at times when evaporation rates are low. Water is a valuable commodity and far more plants die from over watering than from under watering. It is best to water manually where possible and use your automatic watering system when on holidays.
An occasional long deep soak is generally better than watering all the time. Observe when your plants require water or when the soil is dry underneath and water at this time.
Laying Instant Turf
When instant turf is laid it requires constant watering for several weeks until it takes root. This can cause surrounding garden beds to become water logged. When making a new landscape with instant turf, establish the turf before making and planting the garden beds. If you are establishing turf with established garden beds consider hand watering the turf to keep it wet without water logging the surrounding garden beds.
Digging a Hole for a Plant and Throwing Away the Parent Soil
Often when people dig a hole for a plant and discover the soil in the hole is very hard or heavy clay they remove the original or parent soil from the hole and plant their tree or plant with some potting mix, compost or garden mix that is softer and more porous with a lower density than the original parent soil,this is a recipe for disaster! The flowing of water takes the course of least resistance and the hole fills with water, the organic matter in the new soil will decompose and the plant will get wet feet. When digging a hole in heavy or dense soil replant using 80% parent soil and only 20% soil additive.
The soil additive should not contain animal manure or fast decomposing organic matter. Instead it should only contain washed river sand, mineral gypsum or slow decomposing organic matter such as composted pine bark. Use only slow release fertiliser such as Devotion™ Time Release fertiliser. Provision for drainage should be made where necessary.
COMMON WET FEET MYTHS
There are a number of popular myths about wet feet that defy the laws of physics.
I have sloping land so I can’t get wet feet.
People on sloping land are actually more likely to get wet feet as water flows downhill. Poorly drained garden beds and planting holes will flood more quickly and more often on sloping land. People with heavy or non-porous soil on sloping land who dig planting holes are more at risk of wet feet than people who dig planting holes in flatter land.
I will put pebbles, gravel, bricks, clay breaker, compost in the bottom of the hole to make the water go away.
If you dig a hole in impervious clay the only thing that will make the water flow away is a drainage channel or a pipe. If you fill your bath with water the way to empty it is by pulling the plug out.
If I dig a really big hole the water will go away.
Theoretically this may work, but you may have to dig to China! When digging in impervious or poorly drained clay soils a big hole will simply hold more water. The only thing that will drain a really big hole is a drainage channel or an agricultural pipe.
I just won’t water my plants.
Not watering as an alternative to providing good drainage doesn’t work in Melbourne, as Melbourne has prolonged periods of rain that will saturate any poorly drained area.
IDENTIFYING A POTENTIAL WET FEET SITUATION
If you have an area where you suspect you may have wet feet, dig a large hole to the depth that you intend to plant your plant to. If you are planting an advanced plant you will need to dig a very deep hole. Fill the hole with water several times. The hole should drain within 20-30 minutes after the second filling with water. If the hole doesn’t drain you have a potential wet feet problem.
PREVENTION OF WET FEET
Don’t ever use 3 way, 4 way or organic soil mixes that contain a mixture of fine sand and animal manures. You can get wet feet even if your garden beds are well drained using these products.
If you have identified a poorly drained area you can:
- Use wet feet hardy plants as listed under “Plants at low risk of wet feet “. Celtic Cascade® Salix caprea ‘Pendula’, is one of the best.
- Ask our nursery staff for assistance to help you select wet feet tolerant plants.
- Provide drainage using washed river sand, mineral gypsum at the rate of 3kg per m 2 and composted pine bark throughout your soil to improve porosity, don’t use more than 20% volume additive to the parent soil, we recommend Devotion™ Planting Mix For Wet Feet, Heavy & Clay Soils.
- Use only slow release fertiliser such as Devotion™ Time Release fertiliser.
THREE GOOD WAYS OF PROVIDING DRAINAGE
- Cultivate a circle approx. 4ft wide x 1ft deep and add several wheel barrows full of loamy soil. Mix this with your parent soil and create a mound. Many trees such as Silver Birch, Elm, Pine and Oak will die if planted in water but will quite happily grow their roots down into the water.
Dig a hole 18 inches to 24 inches deep x 4ft across then dig a trench and lay agricultural pipe to connect with the nearest storm water pipe. Put a gravel bed in the bottom of the hole so that the water drains to the storm water pipe.One agricultural pipe if laid strategically through the garden can drain many trees and shrubs. Then fill the hole with a mixture of 80% parent soil and 20% washed river sand, composted pine bark and 3kg/m 2 of mineral gypsum. Sometimes the stormwater pipes are buried near the soil surface and an agricultural pipe connected to the stormwater pipe will not provide drainage for the entire root zone of the plants being planted. If this is the case the garden bed can be mounded or raised to provide suitable depth of soil for the agricultural pipes.
If you are planting into poorly drained soil on sloping land, you can drain tree root zones without connecting to a storm water pipe by digging a large hole with a narrow trench running downslope from the hole.Then fill the bottom of the hole and trench with gravel. Fill the balance of the hole and trench with a mixture of 80% parent soil and 20% washed river sand, composted pine bark and 3kg/m 2 of mineral gypsum. Plant your new tree or shrub in the top of the hole. Water will now drain from the base of the hole through the gravel in the bottom of the trench.
PLANTS AT RISK OF WET FEET
Many plants are affected by wet feet but from analyzing our customers’ complaints and problems here are some of the most at risk plants. If you are planting these types of plants be diligent to avoid wet feet.
Plants at risk of wet feet include:
Weeping Cherries, Weeping & upright Silver Birch, Pittosporums, Mop Tops, Gardenias, Rhododendrons, Proteas, Azaleas, Standard Ficus, Standard Blue Potato Vines,BoxOz® Lonicera, English Box, Weeping & upright Japanese Maples, Citrus, Fruit Trees, Standard Roses, Lavender, Silver Bush, Powton® Sapphire Dragons and Myrtus Luma.
All very large advanced plants are more at risk of wet feet as they have a large root mass and require a deeper hole, which means that the bottom of the root mass is more likely to be planted in poorly drained sub soil, therefore exposing a larger more vulnerable plant to wet feet.
PLANTS AT LOW RISK OF WET FEET:
All plants can be adversely affected by heavy soil and wet feet but these plants seldom have wet feet problems or generate customer complaints.
Plants at low risk of wet feet include
Celtic Cascade® Salix caprea ‘Pendula’, Evergreen Cascade® Alder, Toorak ‘Gum Tree’™ Alder, Dwarf Nandina, Mondo Grass, Bongo Borders® Liriope, Photinia Robusta, Box Leaved Privet, Carpet Roses, Rock Roses, Seaside Daisy, Castlewellan Gold Cypress, Neighbours-Be-Gone®Trees, Acmena smithii , Chinese Elms, Plane Trees, Ash Trees, Hydrangeas, Viburnum, Wiegelia, Golden Diosma, Callistemon, Melaleucas, Tea Trees and Eucalyptus.
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