How to Water
The best way to water is with a watering can with a fine spray, which distributes water evenly and so won't compact the soil. If you don't have such a can, place a piece of slate or old crock in to the corner of a pot, tilted downward, and gently pour water onto it. This method also prevents soil compaction and gives an even distribution of water. Repeat in each corner.
Boosting Moisture Levels
Mix water-retaining gels with soil (following the manufacturer's instructions), and spread evenly. The gels absorb water and swell to many times their own weight, releasing moisture to plants over several seasons. Plants that benefit most from such gels are those that grow rapidly and are planted in light soil, from which moisture quickly evaporates.
When to Water
Potted plants need watering all year round, except in freezing conditions. In winter, the rain may do it for you, but keep checking because foliage can act like an umbrella, or a wall can create a dry spot. Water in the early morning or evening when evaporation rates are lowest. Use a rain barrel to collect rainwater for watering mature potted plants; use tap water for seedlings and young plants.
Keeping Baskets Moist
In hot summer winds, hanging baskets dry out more quickly than most containers. Use water-retaining gels to help counter this, and invest in a special extension hose so that you don’t have to hold up hefty watering cans and can target the soil in your baskets more easily.
Automatic Watering Systems
These are expensive and can be a little tricky to install, but they are very effective, water-efficient, and particularly useful when you go on vacation. You set the times when the system starts and stops, and determine how much water is needed. All you need is an outside faucet and an adjacent area where plants can be lined up. If you're away for a long time, ask someone to check that the system is working properly.
Rescuing Dried-Out Pots
If the soil in the pot has shrunk, add a few drops of dishwashing liquid to the water in your can to help re-wet it. For badly wilted plants, stand the dried-out container in a bowl of water and place it in the shade for about 30 minutes; then remove from the bowl. If the plant has collapsed, submerge the pot in a bucket of water until no more air bubbles escape, then remove and leave it in the shade until next morning.