By Matt Gibson
Capillary mats are a heaven-sent gift when it comes to taking care of seedlings. They are also a great hack you can use to help with watering your plants while you are away on vacation. There are some drawbacks to using water mats to keep your houseplants hydrated, but as with most innovations, when they’re used correctly, capillary mats make a gardener’s life much easier.
In this article, we take a close look at water-storing capillary mats. We break down how to use them, when to use them, why you may want to use them for certain jobs but not others, and more. We’ve suggested making your own capillary mats at home as well as including a few links at the bottom that give instructions on how to make your own mats. However, we also take a look at the capillary mat brands that are available at garden centers and nurseries. To become a water-storing capillary mat expert, just keep reading.
What Is a Water-Storing Capillary Mat?
Capillary mats, also known as self-watering trays, are a very useful tool for anyone who is germinating seeds or seedlings. They are also a handy way to water your plants while you are on vacation or whenever you may need a few days off from gardening responsibilities.
Early in their history, capillary mats were primarily used in greenhouses and hydroponic growing systems, so they were not commonly known to the average gardener. These days, self-watering trays are inexpensive, available to the public, and used widely by home gardeners around the world to start seeds and to provide water from the bottom to the top for plants that are sensitive to crown rot.
The mats themselves, are made from an absorbent material, such as felt, or any other water-absorbent fabric that is not susceptible to rot or decay. One end of the fabric dips down into a water reservoir, while the other side of the fabric provides a flat surface. The pots that sit atop the mat then draw water up from the reservoir below, keeping the soil consistently moist, instead of allowing it to swing between the extremes of dry and wet.
These conditions are not suitable for all plants, especially those that are native to arid climates and prefer to have their roots dry out completely between waterings. However, a consistently moist environment is perfect for germinating seeds and seedlings, as well as for raising plants that are more suited to tropical environments with lots of moisture.
Why Gardeners Love Self-Watering Mats
The entire setup is no larger than a three-ring notebook and provides enough room for around 24 seedlings, giving each a cell that’s approximately an inch by an inch and a half square to grow in, totalling about one square foot of space. These setups are available commercially and can be purchased at your local nurseries and gardening centers.
For the more thrifty gardener, the setups are quite easy and relatively inexpensive to make for yourself. Not only will making your own storage mats save you a good deal of money, it will also allow you the freedom to tailor-make the mats to suit your space, as they can be sized to fit in place wherever you need them.
Self-watering mats also include a clear plastic cover that helps to retain humidity during germination, which can be tucked away neatly when not in use by sliding it underneath the reservoir. When you turn the container over, the reverse side looks like a pegboard.
When seedlings are ready to be transplanted, simply flip the container over, then pop them out of their individual cells. The plant’s root systems will work to hold the soil together during transplanting, thus offering the seedlings a bit of support and stability during the transition from their starter home to their permanent home in the ground or in the container of your choice.
The Downsides of Watering Mats
Every great invention has a few drawbacks. Sometimes, new ways of tackling tasks come with hiccups and kinks that need to be worked out or counter-balanced in order to ensure success. Capillary watering mats are no different. The trick is knowing when those drawbacks will affect you—so let’s take a look at the downsides of water-storing capillary mats so you can determine whether they’re the best option for your garden.
When water evaporates at the soil’s surface, the fertilizer that you used to boost your garden’s growth leaves salt deposits on the top of the soil. These salts can draw water up from the roots of your plants and effectively dry out the garden environment completely.
This is usually not an issue for gardeners who are using watering mats as a starting kit for seedlings, as care is generally taken not to over-fertilize seedlings in general (and seedlings don’t usually spend enough time in their starter trays to suffer from this issue). If salt accumulation becomes a problem for you, all you need to do to rectify it is to occasionally water the setup from above to wash out the unwanted salts.
Another issue that gardeners run into is that of available space, when seedling roots begin to grow through the bottom of the cells and work their way into the matting material. This can become quite a problem when you try to remove the seedlings for transplanting, as their entangled roots make them a chore to remove—not to mention the root systems can be severely damaged when it comes time to remove them from the mats and put them in the earth.
Another issue you will want to take care to avoid, despite the hands-off nature of self-watering mats, is general neglect. If left unchecked, water levels in these setups can become too high or fall below the level that keeps your plants or seedlings happy. It’s easy to forget about upkeep when such a large part of the job is taken care of for you, as is the case with self-watering systems.
Be sure to check the reservoir levels often to keep your plants healthy and happy. Despite these few drawbacks, watering mats have proven they can be a big help for many busy gardeners. Without them, gardeners are tasked with spending a lot of time babying seedlings from April to May of each year.
DIY Capillary Mats From Household Items
Ken Sanderson, a horticulturist from the Alabama Agricultural Experiment Station at Auburn University, fashioned his own capillary matting system out of black plastic trash bags and used newspapers. Line your greenhouse benches (or small mat setups for container gardening) with black plastic trash bags to retain moisture levels.
On top of the lining, stack seven to 10 sheets of used newspaper over the plastic, then sit the plants directly on top of the newspaper. Now, instead of watering the soil in the plant containers, you’ll hydrate plants by watering the newspapers themselves.
This setup is especially helpful for gardeners who are dealing with small seedlings and other delicate plants, as directly watering the, fragile foliage of these plants could result in some unneeded damage. Watering the newspaper beneath them keeps delicate stems and roots well out of harm’s way, though.
This system is also preferable to many commercial setups that have been reported to have some issues with insects or fungus, as Mr. Sanderson’s DIY method, if well maintenanced, is safe from infestations. Avoid using newspaper with lots of colored ink, as this ink may contain toxins that you don’t want your plants to ingest. After about 10 weeks, you will want to compost or throw out the newspaper and replace it with new sheets.
Want to Learn More About Watering Mats?
Check out our very own how-to guide to make your own capillary watering mats:
Or use this tutorial video to make your own simple capillary watering mat system:
This useful video highlights watering mats and several other houseplant watering hacks
This guide shows how capillary matting works and how to make your own simple matting system: https://home.howstuffworks.com/how-to-care-for-house-plants2.htm
Watch this short tutorial to find out how to make your own self-watering seed tray: https://www.youtube.com/watch?v=EzyJP8w18KU