Plants get their water from the soil via their roots, and a small proportion is taken through their leaves (but remember that some plants cannot tolerate water touching their leaves). Because plant containers are small, their roots only have a small amount of potting soil to draw water from. This is why the container gardener has to carefully watch plants for signs of underwatering (and overwatering) and water often, especially on hot, sunny and windy days, when plants and their potting soil can lose dangerous amounts of water.
When watering, the plants in your balcony garden, make sure the water penetrates down through the container, rather than just the surface of the potting soil. Let the water slowly make its way through the plant container until extra water drains away. If a plant is extremely dry, allow the container to sit in the drained water for about a half an hour. Do not leave plants to sit in water for long periods of time because soggy roots can rot, and this can kill the plant. After a half an hour, discard any extra water in the container's water tray. If you have overwatered a plant, tip the container to allow extra water to drain out.
If the potting soil completely dries out, there will be a gap between the soil and the sides of the container. If you water a container plant that has had this occur, the water will quickly drain out without the potting soil soaking up much water. To water a container with this problem, insert a stick into the soil in multiple points and water slowly into those holes.
7 Watering Tips
1. Choose plant containers for shape and construction. The shape and material of your garden's plant containers can affect how fast the potting soil dries out. Terra cotta containers, for example, are porous and dry out quickly. Wide-rimmed plant containers dry out faster than those with less surface area of potting soil.
2. Use plastic when planting. If you have terra cotta plant pots or hanging containers with coconut lining in your balcony garden, you will notice that they dry out extremely quickly. When planting these types of containers, place a plastic bag inside of the container before filling it with potting soil – this will help insulate and reduce moisture loss. Make sure to punch holes into the bag to allow for drainage.
3. Keep appropriate container plants. Keep plants from your area, especially if you are in a desert or drought-prone area. Bog plants, for example, are probably not appropriate for small terra cotta containers in balcony gardens in the Desert Southwest.
4. Water at night. The best time to water container plants is in the evening (early morning is good, too). The plant roots will have more time to soak up water before the sun comes out and dries out the potting soil in your balcony garden.
5. Use mulch. Mulch or pebbles on the soil’s surface can reduce the amount of water that evaporates from the plant container.
6. Keep plants out of sunny spots. If a plant in a very sunny spot in the garden dries out constantly, consider moving the container to a shady balcony spot.
7. Water-retaining crystals. You can also purchase water-retaining crystals for your garden that can be incorporated into the potting soil.
Check your balcony garden daily to see if the container plants need to be watered. Stick your finger into the potting soil, and if the soil is dry up to the second joint on your finger, you should water. Dry or wilting container plants also need water immediately.