Good drainage is essential when you’re planting into a container.
It’s true that plants need plenty of water, but waterlogged soil just rots your plant roots.
Good drainage can make the difference between beautiful, healthy plants and those that die after a few weeks causing disappointment and expense.
Creating good drainage isn’t a waste of time – it’s going to save you money in replacement plants!
Let’s take a look at what I think makes good drainage for both outdoor and indoor planters.
Outdoor container plants are at your mercy. In the border any excess rain and hosepipe drenchings can run off, but water gets trapped in containers without drainage holes.
The very first step is making sure your container has drainage holes.
Here I have two types of containers. One has a large drainage hole, the other lots of smaller ones.
One Hole Container
In the bottom of a single drainage hole container, you need a ‘crock’.
A crock is a piece of broken pot with a slight curve. Old broken terracotta pot shards are perfect. This crock allows drainage beneath, but stops soil washing from the drainage hole.
If you don’t have one then look for a naturally curved stone, a seashell, or even a piece of polystyrene with a small section cut out like a bridge, or you could use some weed membrane.
Multiple Hole Containers
The second type of container has lots of holes. I grow cherry tomatoes in a series of these containers. The best thing I have found are numerous pieces of crock to cover the holes.
I have also used weed membrane and those polystyrene packing peanuts – both worked.
I must just report here that the Royal Horticultural Society say that you don’t need any drainage materials in containers with lots of small holes.
I have tried this tactic and it works with very small drainage holes, but the holes in my tomato pot above are too big so the soil runs out. Big drainage holes need a crock or some weed membrane.
Once you have sorted your internal drainage, it’s a good idea to put your container on feet so water can run freely from the base like this.
In summer you can get away with a saucer that stops water running over your deck or patio, but in the cooler months, rain needs to run free.
Houseplants have a different set up. They will have a ‘liner pot’.
This is the pot that a plant is sold in. It will have drainage holes in the base, but is not particularly attractive – take my peace lily liner pot for example.
Does this even need drainage material in the base? It really depends on the size of the holes.
If soil escapes when you water it, then you should probably put something in there to trap the soil but let out excess water.
I’ve used a muslin cloth like this – coffee filters work well too.
A liner pot should always go inside a display pot like this. The display pot will not have drainage holes.
When watering a houseplant you should take the liner pot out, soak it in the sink, let it drain and replace it in the display pot.
While were talking about watering, only water your houseplants when the soil is dry down to a few cms. The number one killer of houseplants is excess water.
Good drainage in a container is something that allows excess water to escape and stops soil wash out.
If you choose good quality potting mix and add perlite to species that need really, REALLY good drainage, such as succulents, then that’s enough – you don’t need to put anything in the pot’s bottom.
It might seem radical, but I would suggest making sure there are drainage holes in the pot, and if the drainage hole or holes are large cover them with a crock or weed membrane.
That’s it! Nothing else. No stones or rocks or gravel. They don’t do a good job, often trapping water in the roots. Filling a container with stones and gravel also makes them really heavy.
The best drainage = crocks or membrane.