Perhaps one of the biggest problems I've had with my plants is watering properly. Some plants require more water than others. But how do you know? Most times your plant will tell you and I hope to share some of the signs with you here.
The first and easiest place to check for moisture needs is your soil. If you have container plants, the surface of your soil should be damp, not soaked. Containers should have some form of drainage, at least one hole in the bottom so that excess water can seep out.
When watering container plants, water at soil level, around the perimeter of the pot. Not at the stem of the plant where the plant enters the soil. You don't want to wash away the soil from this area as you will expose the root system to the elements. Water slowly, allowing the water to soak into the soil. When the water starts to pool on the surface of the soil you have watered enough. If the water seeps out of the bottom, the soil in your container can not absorb any more moisture and additional water will lead to root rot.
When watering larger areas like flower gardens or vegetable gardens it's always best to water the ground instead of using a sprinkler or spray nozzle on a hose. Soaking the soil around the base of the plants instead of spraying the leaves will get moisture to the roots, which is best for strong plants.
Adequate moisture will promote root growth. Focusing water at the leaves and not allowing the water to soak into the ground will keep the roots from growing further into the ground. The roots will remain short, shallow and not produce large plants or fruits. Watering less often but more thoroughly, really drenching the soil will encourage deep root growth and stimulate larger fruit.
Signs of too much water:
1. Yellow leaves
2. Drooping plant
3. Stunted growth
4. Brown spots, mold
5. Wet, sour smelling soil
6. Leaf curl, see pic
Signs of inadequate water:
1. Spotted leaves
2. Dropping leaves
3. Dry, cracked soil
4. Brown, crisp leaves, see pic
If you suspect over or under watering, adjust moisture for a week or so. Plants really are like people and can recover from being "sick."
If you change your watering habits and the plant hasn't rebounded there is likely another cause. In the case of container plants, larger plants will outgrow their pots and need to be moved. Soil can become diseased. Bugs can bring blight and other issues that can't be remedied.