Containers provide great flexibility in a garden-they allow you to garden in a restricted space and grow plants which require specialized soils. Containers can also be used to  restrict the growth of plants that might otherwise take over the garden, such as lemon thyme or mint.  However, providing adequate water to containers provides some challenges.  Because the plants are grown in a confined space, the root system does not have the ability to go in search of water- the plants must make do with whatever water the gardener provides.  Use some of the following tips to keep your plants well-watered!

First things first- know your plants!

Not all plants need equal amounts of water.  Succulents, for example, are more drought tolerant. Read the labels when you purchase plants  and observe your plants over the growing season so that you become familiar with their watering needs.

Know your  containers

• Different containers have different abilities to retain water.  Unglazed clay or peat pots need more frequent watering. Metal or black containers absorb more heat.  Research your containers so that you can water appropriately.

• Insert a plastic pot into an unglazed container to help retain moisture.

• For  concrete containers, consider raising them on a higher surface, such as a table or a pallet to allow air movement.

Make sure your container has drainage holes

Without drainage holes, the pores in the soil will fill with water and the roots will not be able to get oxygen for respiration. Soggy roots could lead to a dead plant. Ensure that there are drainage holes of about 5mm in diameter.  Drill drainage holes if your pot does not have any. If you are really attached to a container without holes,  place your plant in a container with holes and then place it in the  nicer container without holes.

Choose the right growing media

• The type of growing media will affect how often you need to water. Look for a growing media that is high nutrients, has good water retention and good drainage.  Use a soilless mix for hanging baskets to mimimize weight. Consider making your own mix if you are planting a lot of containers. A good growing media is one part garden soil, one part soilless mix and one part compost or composted manure.

• Mix polymer gel with your growing media. Polymer gel expands when wetted, absorbing about 200 times its weight in water.

• Fill the pot to within 20cm of the top- Not filling the entire pot ensures that the media does not run out when you water.

• Do not pack the soil into your containers-  compacted soil decreases aeration, which decreases the availability of nutrients to the plant.

When to water

• Plants that begin to wilt are stressed. They do not have enough water for photosynthesis or to maintain plant turgor. Water plants before they begin to wilt. Stick  your finger in the soil up to the second knuckle- if the soil is dry, it is time to water.  In the heat of the summer, plants in containers may need to be watered daily.

• If your containers have really dried out, poke holes in the soil with a pencil and apply water to the holes

Best time to water

Water in the early morning. Plants will absorb the water before the evaporation rates increase with the heat of the day.

How to water

• Use the mist setting on your hose and water until water runs out the drainage holes. Using the mist setting allows the water to be absorbed slowly, ensuring that the entire media is wetted.

• Water in two stages- water slowly first, and then come back and water again.

• Consider using a watering wand- it extends your reach and allows you to get water to the soil rather than the foliage.

• Purchase a self-watering container. A self -watering container uses the capillary method- water will be absorbed from the bottom of the pot and ensure that the entire media is wetted

• Install a drip irrigation system and attach it to your hose or to a rain barrel, Drip irrigation saves time, especially if you install a timer!

• Caution: make sure that your plants are not standing in water. This can lead to the rotting of the roots.

Conserve moisture

• Add a layer of mulch to the top of the pot.

• Group your containers so that watering is easier.  Place your  containers in a group so that the shade from the taller containers will help conserve moisture in the shorter ones.  Grouping containers also helps to increase the relative humidity.

• Place landscape fabric on top of the soil. Cut  slits in the fabric and then place your plant in the soil. The fabric will help conserve moisture.

• Line the insides of your pots with bubble wrap- it  not only helps to conserve moisture but also  protects plants in the winter.

• Add a layer of gravel to the top of the container.

References

Beckett, Kenneth., Carr, David., Stevens, David. The Contained Garden. NY,NY: Viking, 1993.

Clay, Henry., Lewis, Jeff. “Gardening in Containers” University of Georgia Extension. www. extension.uga.edu.

Editors of Fine Gardening. Tips for Container Gardening. Newton, CT: Taunton Press, 2011.

Grant, Bonnie L. “Container Plant Watering: How much and how often to water potted plants”. www.gardeningknowhow.com

Hardy, Janice. “Container Gardens”. www.haliburtonmastergardener.com

Harrison, Joanna K.,Smith, Miranda. The Container Gardener’s Bible. Emma’s, PA: Rodale Press. 2009

Lerner, Rosie B. “Container and Raised Bed Gardening”. Purdue Extension. www.ag.purdue.edu

“Successful Container Gardens” University of Illinois Extension. www.extension.illinois.edu

Submitted by Sabine Behnk