Outdoor potted plants, under constant sun and other drying elements, have greater watering needs than most indoor potted plants and plants grown in the garden. Fortunately, with a couple of proper water techniques and some persistence, your outdoor potted plants can thrive.
Cover the soil in your outdoor potted plants with several inches of mulch, such as bark or pine needles. This will help retain water and keep the soil cool so the roots do not dry out and possibly fry to death.
Water outdoor plants in the early morning or evening when it is cooler. Water evenly on top of all the soil, not just next to the stems. Only water only as fast as the soil can absorb it and stop when the water drains out the drainage holes. Do not water the foliage or flowers since that may cause flower loss and fungus growth on the leaves.
Check the soil each day during summer. During hot weather, the soil in a potted plant will dry up quickly. Stick your finger about an inch into the soil. If it is dry, then water it as described in step 2. For smaller pots and hanging plants, especially those in the sun, you may need to check the soil in both the morning and evening. During cooler weather, such as early spring and fall, you may only need to water your plants every few days.
Empty the water out of pot saucers or containers after it rains. When you are away or on the hottest days of the year, it's fine to let your plants sit in container of water, but overdoing it may cause root rot.
Use a watering wick as an alternative watering device. These are available for purchase or you can make your own. Fill a bottle--up to 1 liter--with water, quickly flip it over with the cap off, and stick it several inches into the soil. Refill as necessary.