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Marin IJ Articles

The right amount of water at the right time

  • Nanette Londeree
  • Plants, like every living thing on the planet, need water. This essential liquid is vital to the germination of seeds and growth of plant roots; it carries nutrients from the soil to plant tissues, helps to maintain the turgidity of cell walls, and cools the plant. Providing your plants – trees, shrubs, lawns, vegetables, houseplants or whatever you are growing, the right amount of water at the right time in the most efficient and effective way, can be a challenge.

    Either too little or too much water can have a serious impact on your plant’s health, and often, by the time you see signs of distress, it may be too late. When there’s not enough moisture in the soil, foliage can fade in color and wilt, turn brown and die along leaf margins and tips, and drop prematurely. Prolonged or chronic lack of moisture can result in fewer flowers and fruit, slower growth, smaller leaves, and increased susceptibility to plant-killing pests. Even in winter, too little moisture can increase the risk of plant damage from frost as dry soil is less able to absorb and radiate plant-warming heat.

    On the flip side, too much water, be it from Mother Nature during heavy winter rains, poor drainage, or incorrect irrigation methods, can be deadly. Healthy soil is composed of soil particles, air, and water. Air in the soil is vital for plant growth, providing oxygen for roots and soil organisms. When water fills up all the available air spaces in the soil (commonly called waterlogging), oxygen is not available to plant roots, suffocating them and making them more vulnerable to attack by disease-causing organisms. Foliage of plants that have been waterlogged for a short time may wilt and drop prematurely. Signs of edema, brown or tan blister-like areas generally on the undersides of leaves, may appear. Longer durations of lack of air can kill roots, stunt growth, cause abnormally short shoots and small leaves, and may lead to the gradual decline and death of the plant. Waterlogged soil may smell like rotten eggs, be bluish gray or black, and roots may be discolored, rotted, or water-soaked.

    Periodically checking the level of moisture in your soil, especially if you have an automated system, can prevent extremes. The simplest tools for the job are your fingers. Prior to the next time you irrigate an area of the garden or a plant in a container, poke a finger into the soil, penetrating the top three to four inches, and repeat in a few different locations. Is the soil evenly moist? Wet? Bone dry? Depending on what you find, you may need to change your irrigation practices. If you want a more accurate measurement, you can buy an inexpensive moisture meter. Simply stick the probe into the soil to the desired depth and it will give you a digital reading.

    Most plants do best when irrigated deeply; it encourages good root development and provides plants with a greater ability to withstand dry periods. Water your plants slowly; apply water within the “drip line” of the plant (that imaginary line of from the outermost leaves of a plant down to the soil), only as rapidly as the soil can absorb it, until it has soaked at least eight inches below the soil surface.

    Paying attention to when and how you water is even more crucial when it comes to young plants.  Your tender basil starts, transplanted tomato seedlings, new bedding plants or young fruit trees, all need more water while getting established. Moving from a cozy container to the open soil in the garden is a big transition and roots need more water, more frequently until they are well established. 

    Diligent observation can help you keep your plants adequately hydrated. Watch for telltale signs of under or overwatering, and if you see any, start investigating immediately.