There's no one-size-fits-all approach to watering—the amount and frequency of watering depends on the size of the pots and plants, as well as the amount of light. It may take a bit of experimenting to find the Goldilocks balance of just right between overwatering and under-watering, but once you've got that down, you can refine your technique and focus on other factors.
While there are no hard and fast rules to watering, which really comes down to paying attention to a plant's specific needs, your judgment can determine whether you produce a healthy, bountiful crop, or one that you'd avoid showing your closest friends. With that in mind, below are a few watering tips to keep your plants in great shape.
Check for drainage: This sounds like a no-brainer, but can easily be overlooked when growing in pots. Without proper drainage, excess water stays in the base of the pot, causing root rot. If the drainage holes are too small, create larger ones by using a knife or other instrument.
Start with a finger: Before assuming your plants' needs, check the soil moisture with the handiest tool at your disposal—your finger. Feel the soil around your plants; ideally the top two to three inches are dry and the soil below is moist. If your garden is outdoors, check the weather forecast to see what's anticipated before watering.
Like in love, timing is everything: It's best to water during the start of the daily photosynthesis period. Watering in the morning provides the best environment for plants to absorb water, especially during warm weather before the hot sun or winds evaporate the moisture. This protects the plants from wilting in the afternoon heat. If mornings aren't manageable, try watering in the late afternoon, but not too late, as the foliage needs time to dry before the sun goes down to prevent the development of fungal diseases.
Deep and sparingly: While seeds and seedlings need moisture close to the soil's surface, more established plants need the water to go deep in order to help develop roots that will go on to find water in the subsoil during droughts.
Don't go overboard: You want damp soil, but there's a fine line between not enough and too much. Overwatering is one of the most common causes of plant death. Avoid having soggy soil five to six inches below the surface, as waterlogged soil can deprive roots of oxygen, which can lead to them losing the ability to uptake water. A sign of overwatering is foliage that begins to brown at the edges and falls from the plant. If that happens, take a step back from watering, and let the plants be. If growing outdoors, do not water every night unless the weather is really hot and dry.
Humus helps: Mixing in some hearty humus can provide water the material it needs to hang on to until your plants are thirsty. Depending on the type of soil used, more organic matter can increase the accessibility of water for your plants.
Get the water just right: Plants dislike water laden with chemicals and water that's too hot, too cold or distilled. The best way to prepare water is to let it stand in an open container for a few days before use (especially if the water is high in chemical content). Using water that's been sitting also allows it to reach room temperature, which prevents shocking the root system with warm or cold water. While using distilled or boiled water isn't harmful to plants, it doesn't contain certain beneficial chemicals needed for growth. Finally, make sure the pH is balanced.
Catch the rain: Plants love rainwater because it is rich in nitrogen and other elements. Rainwater is a great change in diet, especially for indoor plants.
Check the weight of the pot: Lift each pot every time you water to get a sense of its weight (it is heaviest when it's moist, it is lightest when it's dry). Over time this will become intuitive and you'll know when it's time to water based on the pot's weight.
Pay extra attention during flowering: You can positively influence a plant's potency by limiting the watering during this period. That said, you should also check how long after watering your plants start wilting, and regularly water them one day sooner.
These tips are no replacement for common sense and regular maintenance, but keeping these things in mind will likely simplify the daily watering routine.