Watering plants seems simple and uncomplicated. However there are some myths that mislead even the more experienced gardener. A sustainable landscape calls for installing the right plant in the right spot. Making a plant feel at home improves plant health and reduces the need to overuse a valuable natural resource: water.
When choosing plants, first evaluate your existing conditions and read plant labels. If plants like wet feet, you’ll want to put these in areas that tend to have damp soils like near streams, springs or water features and fountains. If you have dry shade, then look for plants that like those conditions. However, if you’ve inherited an existing landscape or experience drought, unusual heat or drying winds, additional irrigation or hand watering may be necessary. Whether you're taking care of an established garden or installing new plants, you’ll benefit from these guidelines and myth debunking tips.
While the general rule of thumb is about an inch or two of water each week with deep, infrequent watering as opposed to the more frequent shallow watering, this really depends on a number of factors. First, consider your soil. Sandy soil is going to hold less water than heavier clay soil. Therefore, it’s going to dry out faster while the clay-like soil will hold moisture longer (and is more susceptible to overwatering). For clay soils (Western PA,) avoid daily light sprinklings, which encourage roots to grow near the soil surface where they're vulnerable to drying out. Apply water slowly so it's absorbed by the soil rather than running off — a soaker hose is ideal. Another advantage of a soaker hose is that you don’t have to stand and direct the spray.
This is why amending the soil with compost is so important. Healthier soil drains better but allows for some water retention too. Applying mulch is also a good idea, reducing watering needs. Weather conditions determine when to water garden plants as well. If it is hot, windy, and/or dry you’ll have to water more often. Of course, in rainy conditions, little watering is needed. Plants, too, dictate when and how often to water. When a plant is first installed, it requires regular watering until it acclimates to it’s new home. (Read on to later in this blog)
Different plants have different watering needs.
Be sure to read water recommendations and growing conditions on labels or reputable website sources. If plants like wet feet and they are planted in a dry soil, they will need more irrigation. Some plants like hydrangea, astilbe and hosta are sensitive to heat and may need more water during hot and windy weather. Vegetables, bedding plants and many perennials have more shallow roots systems and also require more frequent watering, some daily–especially in temps over 85 F. (29 C.). Most container plants need watering on a daily basis in hot, dry conditions — sometimes twice or even three times a day.
The best way to water most plants is by applying enough to moisten the plant's entire root system, and then letting the soil dry out slightly before watering again.
When to Water:
Time of day is key. The most suitable time for watering is morning, which reduces evaporation. But late afternoon is okay as well provided you keep the foliage from getting wet, which can lead to fungal issues.
Wilting is a sign that the leaves aren't getting enough moisture, but that doesn't necessarily mean that the soil is dry. Anything that damages plant roots can cause wilting.
Plant roots need a fairly constant supply of both air and water. Too little water and the roots die from lack of moisture. Too much water and the spaces between soil particles remain filled with water, suffocating roots. Both situations reduce a plant's ability to deliver enough water to stems and leaves, resulting in wilting. A good example of this is an outdoor pot with inadequate drainage holes -- after a week of heavy rain, the plant’s roots become waterlogged. Root diseases, physical damage (such as disturbing roots while you're hoeing) and soil-borne insects can also harm roots to the point that they can't fully hydrate the plant.
Damage to stems can also cause wilting. Some diseases and insects (especially borers) prevent water distribution throughout the plant, causing some or all of it to wilt.
The only way to tell if lack of water is causing wilting is to check soil moisture.
How To Water
The myth that water droplets act like tiny magnifying glasses and burn plant leaves has no basis in fact.
There are good reasons to avoid watering your garden on a sunny afternoon, but causing scorched leaves isn't one of them. Anyone who has watched the sun come out after a summer shower knows that the water quickly evaporates. Try to avoid watering on sunny afternoons to minimize the amount of moisture lost to evaporation, but don't worry about leaf scorch.
Overhead watering isn't the most efficient from a water conservation standpoint, but there are times when it's called for. It's usually best to apply water directly to the soil around plants rather than watering with a sprinkler. Less water is lost to evaporation, especially on hot, sunny days. Foliage stays dry, minimizing disease problems.
But there are times when an overhead shower is called for.
During dry, windy weather, a fine layer of dust can build up on leaves, reducing the plants' ability to photosynthesize efficiently. Another case is if plants are infested with insects, such as aphids and spider mites. Simply hosing them off plants can keep them in check. Gardeners who want to avoid spraying chemicals prefer this method. Finally, heat-stressed plants that have wilted even though their roots are moist can benefit from a cooling shower — the effect won't last long on a sunny day but it may provide some relief.
Even drought tolerant plants need watering.
Many young plants have perished because these drought tolerant plants didn't get sufficient water at installation time and during their first season of growth. When you set out a new container-grown plant, the roots are confined to the shape of the pot. The plants need a consistent supply of water during their first growing season, until their roots grow out into the surrounding soil. Water them as you would your annual flowers in their first season. During their second and subsequent growing seasons, drought-tolerant plants may need supplemental water only during extended dry spells. Note, however, that just because a plant is drought-tolerant doesn't mean it won’t fare better with a regular supply of moisture.
Watering in Newly Installed Plants
(Courtesy Penn State Extension—Advice for PA residents)
Newly installed landscape plants have a unique set of needs. Unlike established flowers, shrubs and trees, new plants experience an adjustment when transferred from container to the ground. To help plants get a good start in your garden, follow these tips from the Penn State Cooperative Extension. If you live in another region, check out your state extension’s planting guidelines.
Soak the plants immediately after planting and check regularly to prevent drying out. Less frequent but deep watering encourages perennials to root deeply. Perennials that are said to tolerate drought are drought tolerant only after they have become established. The addition of mulch will help to reduce the need for frequent watering.
Shrubs and Trees
Water the plant weekly during the first year, except during weeks when it rains enough to wet the top six inches of soil. When you water, be sure to soak the soil by allowing a hose to trickle slowly at the base of the plant and at the edges of the backfill soil. Move the hose around a tree or shrub bed to assure uniform water application. Avoid shallow, frequent watering because it will encourage the growth of shallow surface roots, which will be vulnerable to drying out. Be careful not to overwater. Frequent saturation of the surrounding soil in poor drainage areas could smother the root system. Water only when the soil under the surface is dry to the touch. Continue to monitor new trees for drought stress into their third season. They may suffer from insufficient water even when other established plants in the landscape are thriving.
Water is a precious natural resource that we don’t want to waste. And unless it comes from the sky, it isn’t free. Start by finding out what your plant needs to grow and thrive. Keep an envelope with the original plant tags, or make notes in your journal. After planting the new specimen in the ideal spot, soak it thoroughly and check soil moisture regularly to help it adjust to it’s new home. And follow our guidelines for optimal watering. Your thirsty plants will thank you.
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