Drainage for Container Plants

We love getting questions from our readers, and this is another blog inspired by a query from a friend of ours in Newfoundland who has an indoor garden of her own. She asks: “do i need a pot that drains and a tray or can I just have a pot that doesn't drain?” and that is a good question for both indoor and outdoor gardens. The short answer is “yes, all containers need some drainage” but as always in gardening the long answer is a bit more complicated. So let’s dig in and learn about drainage for container plants and how you can ensure that your container garden gets the right drainage for plant health.

Plants, Soil, and Drainage

Drainage is one of those tricky issues when it comes to plants. All plants have specific needs, including soil moisture levels, and ensuring the right amount of drainage and the right level of watering are essential for keeping plants healthy. That being said, there are a variety of ways to accomplish this and it would seem that every gardener has their own. So if you have a system that works for you and gives you good results, keep using it! The advice we present here is for folks who are finding their way in gardening or new to containers, or who just have a few questions about the best way to make it all work.

There are four factors in container plant drainage: container size, the drainage properties of the container, soil composition, and watering. We’ve discussed container soils and potting mixes at some length elsewhere, so please check out those articles if you get a chance or if you have questions about soil drainage. As for containers, we’ll start by talking about the impact container size has on drainage

Plants need room to grown, and root growth is easy to overlook as it happens (mostly) underground. By ensuring that your container plants have the right sized containers, you’ll both give the roots room to grow and help keep the soil from compacting or getting waterlogged. Larger containers generally require less frequent watering. So, when in doubt it’s generally best to go with a container that’s a little too big rather than one that’s too small.

Container Materials and Drainage

Containers come in a variety of materials. Some are made of breathable fabrics that enhance air circulation and drainage. More traditional materials include things like terra cotta and porous ceramics which allow water to slowly seep through and create drainage that way. However in many places plastic containers are the most available and most affordable. And while plastic containers can work just fine, there are a few things to consider.

Plastics are generally waterproof, meaning that plastic garden or plant containers will hold water unless an opening is made for drainage. Many plastic containers have drainage holes built into them, which helps if the container is used correctly. We’ve discussed on of the biggest gardening myths—putting gravel in the bottom of containers—and why you shouldn’t do it. Containers with holes do belong on a tray to catch excess water, however, and should have enough clearance between the tray and the container to allow drainage to occur. Double potting is also an option; placing a plastic container with holes for drainage inside a larger container without holes allows you to use the outside container while still permitting  some level of drainage. This works well if you have a decorative container you like that doesn’t happen to feature drainage holes. Just remember that with double potting drainage is still limited so keep an eye on your plants!

Watering Plants and Drainage Issues

Which brings us to the last factor in drainage: watering. Over-watering and under-watering are both bad for plants, and even with good drainage chronic over-watering can lead to waterlogged soil. Every plant species has its own watering needs and its own preferred soil conditions, so learn what your plants require in order to thrive and give it to them. Plant tags in containers, either commercial or home-made, can help remind us when and how much to water so we recommending using them!

A good general guideline is to water plants as needed and check their soil regularly in order keep tabs on their watering requirements. You will often see guidelines like “water when the first inch/2.5 cm of the soil is dry” or something similar. These are good rules to follow, but they do require you to inspect your plants and containers regularly.

In conclusion, while there are a variety of ways to ensure good drainage for our plants, from soil mixes to drainage holes and double potting to watering appropriately, they all require us to pay attention to our plants, our soil, and our containers. This is always a good lesson in the world of gardening, and one that we appreciate being reminded of now and then. We hope this blog helps answer some of your questions, and please keep them coming! Get in touch and ask us anything you’d like to know about plants, gardens or related issues and we’ll do our best to answer!