County Connection- Advice from the Heartland

News Release - Floyd County
Roy Ballard, Purdue Extension Educator, ANR

Water in the Landscape..."Waste not, want not"

The problem with writing about a drought is that by the time the story reaches the press, we may well be in the midst of a prolonged period of rain. I hope this is the case this time. In reality, a drought or any significant period without rainfall can have impacts that persist long after the rain finally begins to fall. These effects may show up some time later in the case of perennial plants and often go unrecognized as being "precipitated" (pardon the choice of words) by the earlier lack of water.

While some of us were fortunate enough to have received some rainfall lately, one has to ask oneself, "Is this too little, too late?" For the rest of us, we may have to make some serious decisions about if we should water and which plants will need it or benefit from it the most. Fresh water is not an unlimited resource and deserves to be used wisely. Some predict, and I tend to concur, that fresh water will be the "Blue-gold" of the 21st century. One can only begin to speculate on the impact this will have on economic growth and the regulations which will evolve to restrict water use and water/nutrient runoff. But that's a discussion for another day.

It's a well documented fact that, for life as we know it, plant and animal alike, water is essential. In plants, water generally accounts for 80-90% of fresh weight. Without adequate water the plant cannot produce its own food, eliminate waste products, "breathe" or even maintain its physical shape. This water must be available not only in adequate quantity and at the right time, but it must be of a quality that will not cause harm from pathogens and dissolved toxins. During a drought it comes as no surprise that even if plants survive, they become far less attractive, less productive and more vulnerable to other stressors such as disease, insects, etc.

Water stress, in its most basic form, occurs when the amount of water exiting the plant through transpiration to the atmosphere exceeds the amount of water that the plant is able to absorb from its roots. In a dry, windy environment even plants with adequate soil moisture may begin to wilt. Some plants are well adapted by various means to avoid water stress. Plants with needles or spines have reduced surface from which to lose water, while others have waxy leaf surfaces to retain water within the leaf. Leaf rolling (corn) and even leaf loss (deciduous trees in fall) can be ways for plants to conserve water during times of stress.

Secondary problems may include spider mite infestations; blossom-end rot of tomatoes, squash and peppers; and increased wildlife and insect damage on fruits and vegetables.

While these may be damaging enough, the often insidious long-term impacts of drought can be worse. These may include an increased susceptibility to wood-boring insects, increased susceptibility to diseases, root death, diminished winter hardiness, dieback of terminal branches, and even plant death.

Since our access to water is usually limited due to availability or cost, it becomes evident that we probably cannot save every plant in the garden. Instead, though it is a difficult realization to come to, we probably should begin a form of garden "triage" in which we prioritize not only the level of susceptibility of the plants but also assess their replacement cost, prominence in the landscape, and the personal aesthetic value we place on them. In general, young woody perennial plants may have a higher priority than fruit and nut trees or small fruits and vegetables. Even further down on the list would be the less expensive and more easily replaced plants such as large beds of annuals.

Lawns composed mostly of well-established fescue will tolerate (not thrive in) limited periods of drought. Watering these only seems to increase their level of dependence on water as they come out of dormancy. Increasing mowing height, decreasing mowing frequency and maintaining a sharp mower blade are all helpful at this time. Those of us who resent the time spent mowing all spring should consider this something of a reprieve from the drudgery of walking in ever decreasing circles as we chase our lawnmower. In most cases, grass growth will resume (all too soon) when temperatures cool and the moisture levels increase.

Even when water is available in the garden, there are some considerations that will make it more available to garden plants.

When should I water?

If soil cannot be formed into a loose ball, it is too dry to supply moisture to plants and watering is in order. Remember, however, to consider the depth of the roots of the plants you are working with. If the top 2-3 inches of soil around an established oak is all that is dry, it is most likely not as much in need of water as a vegetable garden in the same situation. Watering in the morning is preferred to reduce evaporation loss and so that plants will not go into the evening with wet, disease-prone leaves. Strive to have all irrigation completed before 10 a.m. (or so).

How much should I water?

In general, one gallon of water per square foot of root zone should be adequate. This depends on soil type, type of plant and plant growth stage. In some of the heavier soils one might expect an inch of water to provide water to the top four to six inches of soil. If the soil is not mulched, this may need to be repeated 2-3 times per week to make up for evaporation. It is important not to assume the water is getting where it needs to go; instead pull, the mulch back and use a screwdriver or trowel to dig into the soil profile to make sure the water is in the root zone and is not running off or being absorbed by the mulch. Water reaching the sidewalk or drainage culvert benefits no one.

How do I apply the water?

Overhead sprinklers are refreshing for us to watch as we try to remember what rain looks like, and they are fun for children to play in, but they are a rather inefficient means of applying water. Much of their water is lost to evaporation and runoff. Instead, gardeners should consider investing in soaker hoses and drip or trickle irrigation systems which keep leaves dry (and thereby reduce foliar disease) and supply water slowly enough for the soil to accept it. If properly designed and maintained, these systems are so efficient that they even share little water with the weeds between plant rows. Most can be placed under mulch and left out of sight.

New trees and shrubs are best watered with a measured amount of water, because it is hard to assess how much water you have applied from a hose. It may be best to run the water into a bucket first. Pour it slowly on the root zone, and time how long it takes to apply a given amount from a hose and then time the application. As an alternative, you might simply run the water into a bucket with a small hole in its side, then leave the bucket at the base of the tree to slowly soak the ground beneath it. Repeat as needed depending on the size of the tree.

In many cases, captured household gray water can be reused around outdoor plants (especially flowers and ornamentals) as long as it has not passed through a water-softening device.

There is little doubt that we will see the end of this dry season, but garden plants we preserve for next year will require some hard choices and some careful water-management practices. This is not the first dry year we have experienced, and it's probably safe to say that it won't be the last. Decisions about plant selection, landscape design and design/installation of irrigation systems should be done with the understanding that dry weather can and probably will return in the future.

In addition to wilting, plants may also show evidence of water stress by any of the following:

• Upward curling or leaf rolling
• Yellowing or browning of leaves, especially along the edges
• Undersized and off-flavor fruit and vegetables
• Undersized leaves and limited shoot growth
• Blossom- and fruit-drop
• Interior needle- and leaf-drop on conifers and evergreens
• Iron chlorosis (leaf yellowing between veins)

Some Cultural Tips to Improve Plant Performance:

• Mulch around plants to keep weed competition down and soil moisture levels up. Remember to mulch no deeper than 2-3 inches total and not to let mulch touching the trunks of trees or shrubs.
• Reduce or avoid the use of fertilizers or pesticides
• Wait to prune until next spring (some of what looks dead may actually leaf out next spring).
• Keep foot and equipment traffic to a minimum on turf.
• Control weeds in shrub beds and in vegetable and flower gardens. They are strong competitors for moisture. Cultivate shallowly.
• Syringe plants during the day to reduce spider mite populations and to cool plants. Water won't burn plants.
• Select plants that are less water-dependant where plants are to be replaced and group them with plants of similar water needs.
• Leave shallow pans of water out for wildlife. Keep birdbaths clean and full. Honeybees will also grow to depend on these, so keep them away from swimming pools, property lines and walkways to avoid conflicts.
• Stockpile organic matter/compost to incorporate into planting beds this fall.

Contact for more information:

Roy Ballard, Purdue Extension Educator in Floyd County by e-mail roy.ballard@extension.purdue.edu or by calling 812-948-5470.

Garden Flowers Fruits & Vegetables Lawn Care Landscape Plants Insects, Pests, & Diseases Indoor Plants

GardenTIPS Home Master Gardeners County Connection Extension Publications Garden Calendar
Kids' Corner Programs/Products Subscribe/Newsletter

The information contained in this web site is specific to the state of Indiana and may not apply in other states.

EEO Statement 1-888-EXT-INFO Purdue Cooperative Extension Service

Updated on May 25, 2007 Copyright, Purdue University, 2002

Contact Us extension@purdue.edu