Use self-watering containers to hydrate plants when you are away

SINGAPORE – The end of the year is when most people will go away on a holiday. It can be a stressful time for plant parents: Will their plants dry up while they are away?

It can be a real worry for high-rise gardeners who grow their plants in pots. The growing media in the containers can hold only a limited amount of water in the root zone.

Some may ask a family member or fellow gardening friend to help water the plants.

An online search will yield myriad ideas and contraptions that can be implemented at home to ensure the plants are hydrated. Some are very affordable and can be easily set up by home gardeners, while others can be expensive and a little complicated to install.

For me, the most straightforward way to ensure my plants are given water during my absence is to grow them in self-watering containers. Whether they are store-bought or homemade, they comprise the same components and work via the same principle.

Components of a self-watering container

A self-watering container is simple in its design. It essentially consists of two containers. An inner container holds the growing media and plant, and has drainage holes at its base. A piece of cloth or netting is placed over these holes to prevent growing media from falling out.

The outer container is a watertight one. Its main purpose is to be a reservoir that holds water in reserve for the plant. It can also play a decorative role – this can be seen in store-bought self-watering containers that come in a wide range of designs.

An essential component in the set-up is a wick made from a water-absorbent material. It is threaded through the inner growing container where one end is stuck within the growing media and the other dangles into the water reservoir.

The wick helps to draw water from the reservoir to moisten the growing media via capillary action.

Some store-bought containers have a clear window in the outer container to allow the home gardener to check the water level in the reservoir. Others have a water level indicator.

Note that self-watering containers are different from hydroculture and semi-hydroponic set-ups. Plants growing in self-watering containers are cultivated in growing media that is kept away from the water reservoir.

In hydroculture and semi-hydroponic set-ups, plants are adapted to growing using large expanded clay aggregate (Leca) that sits in a reservoir of water or nutrient solution.

Self-watering containers are hassle-free as they do not require a growing media change and allow a wider range of plants to be cultivated.

Types of plants suited for self-watering containers

The growing media is kept moist via the capillary action of the wick, which draws water from the reservoir. For this to work properly, the growing media should not be too porous.

The preferred type of growing medium is one made with water-retentive materials such as peat moss or cocopeat.

With these criteria, plant candidates for self-watering containers will be those that can thrive in a constantly moist root zone environment. You can include some gritty growing media amendments such as perlite, vermiculite or pumice to improve aeration for the roots.

A wide range of foliage houseplants, shrubs, small treelets and common edible plants like leafy vegetables can be grown in self-watering containers.

Avoid growing Mediterranean herbs such as lavender and rosemary, and cacti and succulents. These plants prefer their root zone to dry out slightly before watering again and detest constant wet feet that is found in self-watering containers.

Watch for pitfalls

It is important to ensure that there are no holes and gaps in the self-watering containers. These can let mosquitoes enter the water reservoir to lay eggs, leading to a mosquito breeding issue.

Some store-bought products have an inlet that allows the gardener to refill the water reservoir easily. Such openings can be concealed with a piece of washing sponge to deny access by mosquitoes.

Self-watering containers as long troughs are commonplace and popular for growing leafy vegetables. Such containers, when used outdoors, will be exposed to rainfall. To prevent the trough from flooding, a hole at the side of the outer container allows excess water to drain out.

An opened drainage hole will pose the same mosquito breeding risk. You may need to place a netting over it to prevent entry by mosquitoes. Check the container periodically and clear any debris trapped by the netting.

While it is tempting to fill the reservoir with as much water as possible, the maximum water level in the reservoir should not touch the base of the inner container. This is to reduce the occurrence of an anaerobic root zone as excess water will fill the pores in the growing media and suffocate the roots.

Some store-bought self-watering containers have water reservoirs that are made from a clear plastic material, offering a visual opportunity to view the water reservoir level.

Algae growth may occur due to light exposure in self-watering containers made from a clear plastic material, so regular cleaning is necessary to keep the set-up looking presentable. Avoid keeping fish in such set-ups as the leachate from soil-grown plants can be harmful to aquatic life.

Making your own self-watering container

A self-watering container can be made from upcycled materials, but you will need an inner flower pot that fits snugly with an upcycled outer pot.

I use a recycled translucent plastic food container. A wick is cut from a polyester table throw. The same material can be cut to size to cover the drainage holes at the base of the pot.