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The health and well-being of all our plants, both indoors and out, ultimately comes down to watering. It’s a very complex issue that is dependent on many factors, such as the type of plant, the kind of soil in which it’s growing, the time of year, current weather patterns and so much more.
I would venture to say that the greatest number of plant problems and plant deaths are due, in large part, to improper watering.
At this time of year, when we have a prolonged stretch of dry weather and above-normal temperatures, I’m particularly concerned about the survival of many trees and shrubs. When any plant develops moisture stress, either from too much or too little water, it becomes far more susceptible to insect and disease problems, root rot and foliage burn. Finding the right balance of hydration is one of the keys to healthy plants.
Automatic watering systems can be both a blessing and a challenge. They need to be adjustable to current conditions. They shouldn’t be watering the same amount every day for the same time period without regard to the type of plants, their location in sun or shade and the nozzle head used to pattern the water flow.
Another issue when watering, especially with automatic systems, but also with sprinklers, is water efficiency and how much water shoots onto sidewalks, driveways and roads day-after-day. Water needs to be targeted to lawn and plant areas, not pavement.
Drip systems and soaker hoses are, by far, the most effective means of water distribution because they deliver the water directly to the root zones, where it can be used most efficiently. It’s a good idea, right after watering, to check the depth of water penetration into the soil to see if it has actually travelled down to a plant’s root zone.
The time of day is also critical. Watering in the morning, when the temperature is on the rise, allows the plants to make the best use of the water. It’s very important to have moisture around your plants’ roots during the time when heat stress is the most intense. If you water in the evening, plants transpire much of it away. This is particularly true with lawns and larger trees.
We are now in a period of high humidity, and this is a significant issue in our food gardens. The foliage on some veggie crops can, overnight, develop mildew. As a preventive measure going forward, it’s important to keep water off the foliage of all your tomato, potato, squash, cucumber and melon plants. Around Aug. 15 is the usual time that we start to see late blight on both tomatoes and potatoes.
So, from this point, keep their foliage dry by using a soaker hose or hand-watering with a proper nozzle or water head, and water only the root zone. The best water nozzles or water breakers have either 400 or 1,000 tiny holes to help distribute the water more efficiently. Water thoroughly and deeply to encourage the roots to grow down and to find their own moisture. Watering every day isn’t necessary if the root zones are moist. Don’t be fooled by wilting leaves — this is often a sign of heat stress, not water stress.
The same is true with annuals and perennials. Try to keep water off the flowers and foliage to prevent mildew and many other diseases. These plants, too, need to be watered deeply to facilitate the roots going deeper.
Hanging baskets and containers need to be checked daily for moisture levels. Water them in the morning, if possible, with a thorough, deep watering to get enough moisture in the pots for the plants to withstand the warmest sun. Again, use a proper hose end nozzle and water until the bottom of the container is evenly moist. Allow your containers to dry slightly before watering again. For moss baskets, also water the sides to prevent the moss from drying out.
With the constant summer watering, you must feed frequently or use a slow-release fertilizer to compensate for the steady leaching of the soil. Working organic matter, like Sea Soil, into the container’s soil mix will help hold more moisture in the soil.
All outdoor trees and shrubs need a thorough, deep watering, especially around their driplines where the feeder roots are located. Established trees, depending on a number of conditions, will need watering only once a week, but after watering, you should dig down with a small shovel or trowel to make sure the water has penetrated down to the roots.
Hedging cedars are particularly vulnerable to hot weather because their root systems are very shallow and tend to dry out quickly. A thorough, deep watering once a week should suffice. Placing a layer of fir or hemlock bark mulch (about two-to-three inches deep) around all your trees will help hold in moisture and prevent rapid evaporation.
Newly planted trees will need daily attention during hot weather until their roots expand into their new surroundings and are able to access a greater supply of moisture. Overwatering can be worse than underwatering, so give them a good, deep drink, then let them dry out slightly. Hot weather may cause some leaves on newly planted trees to wilt a bit but just continue keeping the roots evenly moist.
Lawns should be watered once a week to a depth of 1 1/2 to two inches. This will help keep them green, which in turn will cool your yard and allow your lawn to keep providing oxygen and sequestering carbon. As I mentioned in last week’s column, hydrated lawns are a Fire Smart safety measure too.
All our outdoor plants contribute significantly to better environments in our communities. Urban landscapes are becoming far more important than ever before, and properly caring for them during hot weather pays many dividends. So, keeping in mind local watering restrictions, let’s water wisely to protect our plants, to keep them growing and to help preserve our water resources.