Updated/Fact-Chacked on February 25, 2022 by John
Most plants need well drained soil conditions to thrive. If rain water does not drain through your soil, the plant roots will likely rot. Water logged soil can become anaerobic, which means it lacks adequate oxygen to sustain the majority of plant life. Water retention also changes the thermal efficiency of soil, so plants cannot get their required temperatures to grow well.
The two worse types of soil are clay based and sandy soils. Sandy soils will drain water away too quickly, taking nutrients with it, while clay soils hold too much water. Both these conditions can be improved by adding organic matter, along with a few of our tips below.
What is well drained soil?
Soil with good drainage will have plenty of air gaps between solid elements allowing water to trickle down, while giving the roots enough time to absorb all the nutrients they need.
How to check if your soil is well drained
Dig a 15″ inch hole in your soil, ideally use a bulb planter and then fill it with water. The first amount should drain away quickly, then refill again with water and see how long it takes to drain away. Ideally, you are looking for around 1 inch per hour.
Ways to Improve Soil Drainage
Add more plants
The more plants you add to the soil, the more roots you will have growing to absorb rain water. The roots also create more space and air pockets for water to flow down by breaking up compacted soil.
Add wood chips to the surface
Wood chips will absorb some of the moisture and stop rain water being absorbed directly into the soil immediately. Some of this moisture will then evaporate when the sun comes out.
Wood chips also reduce the amount of weeds coming through so it’s a win-win.
Dig and turn the soil regularly
Digging and turning your soil regularly will help break it up and create aeration, it will also limit weed growth.
Add organic matter
Adding organic material from a compost heap can greatly improve your soils drainage, you could also add shredded leaves. This will help both sandy and clay heavy soils. Organic matter can include a good compost, coco coir, worm castings and grass clippings.
Add grit to clay soils
Grit or course sand can be turned into clay soils to improve it’s drainage.
Solutions for severe water logged surface
Install underground drainage
This can be an expensive job and you’ll probably need the help of an external groundworks team. They would dig your garden up and install perforated pipes and run-offs to catch all the excess water and take it away – just make sure they don’t point the run off at your house or a neighbour’s property.
Build raised beds
If the above is too expensive and you want to expand your plant growing area, opt for raised beds – you then have 100% control over the soil quality. Raised beds also allow you to work in the space without having to stand on the soil and compacting it, great for smaller properties and allotments.
Creating good soil drainage in raised beds
If you already have a raised bed in place, all the above tips will help the water drain away better.
If you are creating a new raised bed, here are some tips to build the best drainage system possible.
- Choose a place where the water drainage is best. If the area you have chosen is poor (heavy clay or sandy), carry out some work first to try and improve it. Even if you are building high raised beds, water will filter down to ground level eventually.
- Create your raised bed in the sunniest spot possible to allow water evaporation; also avoid areas where trees may create shade when foliage is out.
- Use a good quality raised bed liner at the base to allow water to drain through but stop unwanted weeds and grass to come through into your raised bed soil.
- Add a stone/gravel base layer on top of the existing soil. A good type is Mot type 1 sub base.
- Add worms to your raised bed soil, they will work for you breaking up the soil.
Soil Drainage FAQs
How can I make my soil drain better?
The fist step is to add more organic matter. You could also try adding vermiculite.
Can plants recover from root rot?
Root rot occurs when the soil is not draining properly, which creates good conditions for harmful fungi. It is hard to save a plant with rotten roots, but try removing the bad roots and re-plant in better conditions.
What does plant overwatering look like?
Look for plants generally wilting and changing colour while the soil is continually wet when you insert a finger.
John Green is a 46-year-old graphic designer living in Durham. John is RHS level 3 certified and owns an allotment in Durham.