It is almost impossible to overestimate the importance of water for your garden – after all, water makes up 85-95 percent of the weight of living plants.
In fact, plants use more water than anything else. Water carries nutrients from the soil to the plant cells, so plants that are kept at their desired hydration level will be stronger and healthier.
It's important to state, that there is NO way in one blog post to teach anyone exactly how to water every garden, every plant, in every climate or region. Instead, we can talk about rules of thumb and suggest tools that will help you understand what to look for when determining watering needs.
There’s a fine balance between too much and too little water. Too much water can result in soggy roots and plants may become oxygen-starved. Clearly, for bog or aquatic plants, this isn’t an issue. But for our perennial and shrub borders, this can be deadly. Too little water and plants can just stop growing, wilt, and eventually die. For plants that have developed to live in more hot/dry/arid conditions, there is clearly a higher tolerance for dry conditions. Knowing your climate and your specific growing conditions – including soil type – must always be the starting point in making watering decisions.
A good rule of thumb is that ornamental gardens require about one inch of water per week. This assumes a healthy soil structure that can hold that water for the plants to be able to absorb it. Gardens located in a hot, dry climate lose moisture at a more rapid rate and may require up to two inches of water per week, while gardens in cooler climates may require no watering at all or minimal watering.
For most healthy garden soils, one good soaking is better than several shallow waterings. This helps to encourage roots to grow nice and deep rather than staying close to the surface awaiting their next quick sip of water. Water that goes deep, can endure longer than the water on the surface which dries up under the hot sun and atmospheric heat.