“Ask the way to the spring.”
— Rumi
Backyard fruit trees cared for and kept healthy with adequate water, sunshine, pruning, and mulch are generally well positioned to resist pests, disease, and other complications that arise. Fruit trees are plants first and fruit producers second. From a blade of grass to an oak tree, plants operate on similar principles. Important for fruit trees, the information in this chapter and the next can also be broadly applied.
Established pomegranate trees like this one aren’t likely to need supplemental water, but newly planted trees surely will.
When I worked in nurseries and talked to customers about their various plant problems, water irregularities caused more trouble and had more ramifications than any other issue. The water needs of fruit trees and other plants depend on constant factors like soil type, and changeable factors, like day-to-day weather patterns. Watering is never a one-size-fits-all proposition.
Water requirements depend, first, on the frequency of natural rainfall. If it rains consistently from spring through fall where you live, watering won’t be much of an issue, except in unusual circumstances. When I moved to Upstate New York, I was astonished to learn that nobody needed hoses, except when they wanted to wash the car. Watering was simple: wait for rain. In places like Portland, Oregon, or Portland, Maine, plants get along just fine without supplemental water most of the time.
In California, however, the rain usually stops in April and doesn’t resume until October or November. This is one of the factors that defines a Mediterranean climate. Most plants here fare poorly without some irrigation. For reasons unclear, plants handle natural rainfall pretty well in places like the Portlands — far more easily than they manage a conscientious gardener in a Mediterranean climate with a garden hose or a timed sprinkler system.
Plants contend with drought situations in a number of ways. Plants that naturally tolerate drought have small leaves or waxy, gray, and fuzzy foliage that both deflect the effects of too much sun and help a plant conserve available water. A pomegranate, for example, tolerates more drought than a persimmon. You can tell by looking. Big, deep root systems have the capacity to collect more water if water is in limited supply. The five-inch oaks that sprout in my meadow have eighteen-inch taproots. Plants without these overt defenses, though, can still handle some drought in the same way that people manage the stress of a few sleepless nights, provided it doesn’t become chronic.
As a plant tries to manage a water shortage, certain routine events tend to occur. Plants that run dry lose their healthy luster. A practiced eye will catch the flat, blue-green color of a suffering lawn by sight, as well as the same dull green of dry plants in the nursery, garden, or forest. Spring growth that follows winter rain or snowfall shows itself in bright, shiny foliage. As the summer progresses in my unirrigated summer-dry landscape, the vibrancy of foliage flattens and grows drab until spring comes again. The native and Mediterranean plants in my garden have adapted to tolerate just these conditions.
Wilting is a plant’s first line of defense against a water shortfall. Wilting has a biological function. When leaf surfaces droop they get less sun, and with less sun the plant preserves its diminishing stores of available water. Plants running slightly dry are also more likely to sunburn. Sunburn looks like sunburn — scorched — and, like sunburn on a person, manifests in a pattern on the parts of the plant that had too much exposure. At the nursery, we always saw lots of sunburned leaf samples a couple of weeks after a heat wave, yet our customers rarely connected a sunburn event to the weather.
Drought stress shows itself from the outside in. With extreme water shortages, water travels through the plant as far as it can go. When a plant runs out of water the tips and edges of foliage dry out and turn brown. If the lack of water recurs consistently — if, for example, a sprinkler system is timed to run consistently a little short — a series of lines appears at the edge of the leaf, one line for every time the water didn’t go quite far enough.
One factor that affects water is soil. The ratio of clay, sand, and silt particles defines soil type. Water penetration improves with more sand particles to separate the silt and clay particles. Does this mean you should add sand to your clay soil? Emphatically not, but more on this shortly.
Clay particles are the tiniest soil particles. They stick together. More accurately, they congeal. If you dig clay soil, it hangs together in a big lump. Water and air won’t move easily through soil that is predominantly clay because the spaces between soil particles are so small. Clay soil is mucky and airless when it’s wet and impenetrable when it’s dry. When you water clay soil, the water slicks out across the surface of the soil in a shallow puddle. Water that confronts heavy soil has a hard time going deep. Roots growing in heavy soil appropriately stay near the surface to get the water and air they need. To compensate for heavy soil, water long and slow. This gives the water a chance to percolate down. Water less frequently — heavy soil excels at holding water. Clay soil is rich in minerals and nutrients because they don’t wash away.
If sand is added to clay soil in the interest of drainage and in inappropriate amounts, the tiny clay particles gather around the sand, much the way cement gathers around sand particles to form concrete. As discussed in chapter 5, organic amendment dug into soil can be counterproductive. Removing “bad” soil and replacing it with “better” soil changes the way water moves through soil and will likely make your problem worse. Develop the soil you have with mulching. As you will learn in the next section, surface mulching is the best way to amend any kind of soil and improve its capacity for managing water.
In contrast, sandy soil lacks enough clay and silt to hold water around roots. The air pockets created by too much sand send water racing down and away from the root zone. Plants that grow in sandy soil need more frequent watering for shorter durations. Plants not naturally acclimated to sandy soils need more fertilizer, too. Roots grow easily through fast-draining soil — they meet no resistance — but this soil type dries out quickly and nutrients leech away with frequent watering.
Gardeners aspire to loam. Loamy soil has a balance of clay, silt, sand, and organic matter that combines the drainage benefits of sand and the water and nutrient holding capacities of clay. In places where loam doesn’t naturally occur, a top dressing of organic mulch will reduce water needs, create healthier soil, and encourage marginal soil of any kind in a loamier direction.
Proper watering allows for an exchange of water and air in the soil. As roots pull water out of the soil, air comes in. Roots need air as much as they need water. Plants affected by over-watering lose roots, not because they have too much water, but because they lack oxygen. Roots without oxygen die off. As the root system in waterlogged soil gets smaller, it tries to maintain a plant that is too big in relation to the diminishing roots. Damage from root rot progresses exponentially. Continue to water as you have been, and the problem quickly grows worse and worse.
An over-watered plant preserves the exterior of the plant at the expense of the interior. In essence, it gives itself less plant to support by losing foliage. A plant sheds yellow leaves from the inside out, yellow foliage that drops or detaches easily when you tug at it. The center and lower parts of the plant are affected first. In contrast, yellow leaves that hold fast to the plant indicate micronutrient or nitrogen deficiencies, not excess water.
Plants with water-damaged root systems have more difficulty recovering than plants that merely dry out. If you catch an underwatered plant in time, the roots hydrate and begin to grow again. In contrast, the small and shrinking root system of a water-damaged plant lacks the capacity of a healthy plant to pull much water from overly soggy soil. The plant can’t do its part to help the soil dry out. Soggy soil stays wetter longer, a big problem for the already waterlogged roots. When the soil does begin to dry out, you must water these plants as soon as they need it and only as they need it to allow the root system to grow large again. Even with a moisture meter, recovery is tricky.
In addition, too-frequent watering keeps surface soil consistently moist. This moist surface favors an environment for many soilborne diseases, especially a problem for apricots and cherries. Water plants long enough to give them a good soak. The size of the resulting root system enables a plant to survive as the surface soil dries out. Dry surface soil greatly reduces the likelihood of disease. Let soil dry at least a couple of inches down before you water again.
Check for moist soil first if a plant is wilted. Plants that wilt when soil is moist don’t need water. When a plant perks up after a hot day at sundown, this means it protected itself from the sun by drooping its leaves, a natural process called transpiration. If the soil is moist, don’t add water. If you water a wilted plant and it perks up, you don’t have a problem. If you water a plant and it stays wilty for several days, you likely have a collapsing root system — damage that might be corrected with careful watering, but is more likely irreversible.
When you do water, water thoroughly. Let plants use up most of the water they’re given, and then water thoroughly again. How often is this? It depends on the situation. Light soils require more frequent water. Heavier soils require less. For established fruit trees in lighter soil usually once weekly is enough; in heavier soils, and as the tree gets older, water once or twice a month or only rarely. If you find yourself watering daily, you’re probably not watering deep enough. Again, proper watering depends on a number of factors — the soil itself, the presence or absence of mulch, the weather, the wind, the time of year, the age of the plant, and the type of rootstock.
The need to water provides an excuse to get into the garden. It keeps you engaged and aware of events there.
While a moisture meter won’t ever replace alert human engagement and observation, this device costs very little and can be helpful as a tool of enlightenment. Water, check the moisture content of the soil around the plant in several places and at different depths with the meter, then check the moisture content before you intend to water again. As you work with the meter, a pattern develops. Things underground might not be as you supposed. Use the plant’s water usage pattern as shown by meter readings to adjust your watering schedule. Let a plant set its own watering pace. A moisture meter can be especially helpful if you’re working out timing for a drip system.
With or without a drip system, most people water too often and not thoroughly enough. A problem with boring insects in young trees suggests the drought stress associated with this kind of watering. Plant roots follow water in the soil. Thorough, less frequent watering results in a plant with a root system big enough to sustain itself in crisis situations — hot days, droughts, and two-week vacations. An extensive root system makes a more resilient plant.
Be aware of a few other considerations. Plants work harder and use more water on hot days. They also work harder and use more water when they are actively growing in the spring. Wind can be more drying than heat. Depending on the soil and type of rootstock, most trees more than four years old manage easily on one deep watering a month through the summer season. Because of their smaller root systems, young plants need more frequent water than established plants, but less than you might think if you water thoroughly enough. Check with a moisture meter if you are uncertain. Nights are longer and cooler in late summer and autumn, even when it’s hot in the daytime. As a plant slows down and readies for winter, it uses and needs less water than it did in spring and early summer. Last but not least, less irrigation makes fruit meatier and concentrates its flavor.
Ultimately, nothing beats a little attention. Water systems on timers encourage inflexibility and detachment that are usually not beneficial to plants. The need to water provides an excuse to get into the garden. It keeps you engaged and aware of events there. Hose-end bubblers, sprinklers, and soaker hoses hooked up to spigots you turn on and off yourself deliver water slow, deep, and as needed.
