What is well-draining soil?
If you’re a gardener, chances are you’ve come across the term ‘well-draining’ soil once or twice.
Most plants, including perennials, annuals, herbs, vegies and fruit trees, love well-drained soil. But what does well-draining soil mean?
Well-draining soil is soil that drains water at a steady rate. Like the character Goldilocks in the fairytale The Story of the Three Bears, most plants prefer soil that doesn’t drain too quickly or too slowly, but is just right. But what exactly is ‘just right’ you ask? Take the simple test below to find out if your soil is well-draining.
A simple test to find out if your soil is well-draining
Dig a hole 30 centimetres deep and wide. Fill it with water. If the water drains from the hole in 10 minutes or less, you have fast draining soil. If the water takes an hour or more to drain, you have poorly-draining soil. If your soil is well-draining, the time the water takes to drain will falls somewhere in between.
What happens to most plants if they don’t have well-draining soil?
If your soil is slow-draining, it gets too wet. Your plant’s roots need oxygen as much as they need water, but if they’re sitting in soggy soil, their oxygen intake from the soil is reduced and they can suffer from root rot, are more susceptible to disease and insect damage and can eventually die.
On the other hand, if your soil has too much air, it will drain too quickly and your plants won’t have enough time to absorb the water. As a result, the roots will dry out and your plant will die. Just like plants that get too much water, plants that don’t get enough water are also prone to disease and insect damage.
I don’t have well-draining soil in my garden. Help!
If you have poorly draining soil, it’s likely you have either clay soil (too slow) or sandy soil (too fast). If you’re not sure what type of soil you have, click here to take the soil type test.
Clay soil drains poorly and causes plant roots to sit too long in wet conditions. If you have clay soil, you need to make it more porous. Clay soil can be improved by adding organic material such as compost, rotted manure and mulch, along with gypsum or clay breaker, before planting. Where digging is difficult, laying organic mulch and manure over the soil to break down, assists over the long term. Learn more about clay soil.
Sandy soil tends to be fast-draining. To improve sandy soil, regularly add organic material such as compost, rotted manure and mulch. When planting, work organic matter into the soil before planting and regularly spread organic mulch and manure over the soil surface to replenish organic matter. For new plantings, line the planting hole with several sheets of wet newspaper. This slows water loss for the new plant but eventually breaks down as the plant gets established. You can also apply a soil-wetting agent such as Wettasoil from time to time to encourage water to soak in. Learn more about sandy soil.
How to create well-draining soil in containers
The good news is, all potting mixes are well-draining, so all you need to do is choose a potting mix that’s appropriate for the type of plant you’re potting up.
Bagged potting mixes are pre-packed with the nutrients your plants need, so there’s no need to add soil, compost or anything else. Buying a potting mix is also far more effective and efficient than mixing your own.
Before adding potting mix, ensure the container has enough drainage holes for its size. Resist the temptation to line the bottom of your container with gravel or similar chunky material, as this makes it harder for water to drain from the soil. In the past, adding a layer of pebbles and/or activated charcoal helped with container drainage, however with the massive improvement in the quality of potting mixes, this technique is no longer necessary.
If you have a plant that’s already in a container, give it well-draining soil by taking the plant out of the container and adding new potting mix at the bottom of the container. Or you can move the plant into a bigger pot with new potting mix. If you have a container plant that you notice water runs off, add Wettasoil granules on top of the soil.