Because it is such a widespread problem, relax, because you’re not alone, and the good news is that with a few rules of thumb, you won’t have to worry about how to water ever again.
A lot of times gardening books will tell you that a general guideline for watering is 1 inch (2.5 cm) per week.
There are a lot of problems with that guideline because it doesn’t address different climates and different times of the year, and while that 1 inch (2.5 cm) may be good for a warm summer day, it may be too much for a plant on a cool spring or fall day.
It also doesn’t address if you get rain, or what your soil type is.
More bad advice is when you’re told to water, then wait for a day or two, and then dig down 2 to 6 inches (5 to 15 cm) and test the soil moisture around the root zone. Yea right, like every time you to want water you’re going to dig around to check. Get real!
Some Good Advice
There are three main things you want to keep in mind:
1. The type of plants you have
Plants with deep extensive root systems, or those that are able to store moisture (like succulents), are able to survive on less water and are drought tolerant, as opposted to non drought tolerant plants that need lots of water to survive.
2. The moisture retaining capacity of your soil
Plants growing in fast draining sandy soil are going to need more frequent watering than plants grown in heavier or well mulched soil that holds water better. If you have sandy soil, you would be wise to consider mulching.
3. Your climate
Do you live in a desert or do you get periodic rain, etc.
A Good Rule Of Thumb:
The best rule of thumb is to water as deeply and as infrequently as possible. Watering to make sure the soil is moist to at least 6 to 8 inches (15 to 20 cm) deep is best because it helps the plant grow its roots deeper into the soil. A note here: We don’t mean to flood your plants! Just a good deep watering, don’t get carried away.
Frequent light watering in not good for your plants because it only wets the surface of the soil which encourages roots to grow upwards in search of moisture. The water evaporates quickly and the soil dries out, leaving the roots in hot, dry soil.
The Best Time Of Day
The best time of day to water is always in the morning. This gives the plant time to absorb the water and get ready to handle heat, cold, or just the energy it takes to produce chlorophyll, grow, and move nutrients around.
If you water in the late afternoon or evening, the problem is that the plant is now wet and the air temperature is cool. Those are the best conditions for mildews, molds, and all kinds of disease problems. Keep life simple, water in the morning.
Finally The Fool Proof Way - The Squeeze Test
Keeping the above in mind, now apply the way most successful gardeners check the soil.
If the soil crumbles apart when you open your fingers, it’s too dry
If the soil holds together without packing densely, it’s just right. It means the soil is slightly moist, and forms a weak ball with rough surfaces, no water staining on fingers, and a few soil grains break away
When it’s too wet, it forms a ball with well-defined finger marks, light to heavy soil/water coating on fingers, ribbons between thumb and forefinger.
Way Too Wet
When it’s way too wet, it forms a soft ball, free water appears briefly on soil surface after squeezing or shaking, medium to heavy soil/water coating on fingers.
So overall, keep in mind:
The plant material
The time of year
Your soil type
Water in the morning
Water deeply and infrequently
And lastly scoop up some soil, give it a squeeze, and see how it reacts
The more you do this, the easier it gets, to the point where you’ll know exactly how much water your plants need, and you won’t ever have to really think about it again.